TM 11-5820-398-35 DEPARTMENT OF THE FIELD ARMY TECHNICAL AND DEPOT MAINTENANCE RADIO T h i s c o p y p a g e s SET i s f r o m HEADQUARTERS, a MANUAL AN/PRC-25 r e p r i n t C h a n g e s MANUAL w h i c h 1 a n d i n c l u d e s 2 .
WARNING DANGEROUS VOLTAGES EXIST IN THIS EQUIPMENT When Receiver-Transmitter, Radio RT-505/PRC-25 is in a transmit condition, 45 volts dc and 125 volts dc are generated in module Al and applied to transmitter power amplifier V1. The 45-volt potential is also applied to modules A6 and A7. Take all necessary precautions. DON’T TAKE CHANCES! CAUTION This equipment is transistorized. Before connecting test equipment within the modules, insulate test prods and clips with insulating tape or sleeving.
2 TM 5820-396-35-CI-9 Figure 5.1.
TM5820-398-35-CI-4 Figure 7.1.
TM5820-398-35-CI-2 Figure 22.1.
Changes in force C 1 and C 2 TM 11-5820-398-35 C 2 HEADQUARTERS DEPARTMENT OF THE ARMY W ASHINGTON , D. C., 22 April 1965 C HANGE No. 2 Field and Depot Maintenance Manual RADIO SET AN/PRC-25 TM 11-5820-398-35, 8 January 1963, is changed as follows: Note. The parenthetical reference to previous changes (example: page 1 of C 1) indicates that pertinent material wae published in that change. Page 3, paragraph 1.1 (page 1 of C 1). Change “AMSEL-MR-MP” to: AMSEL-MR-(NMP)MA. Page 7, paragraph 6b(l), line 3.
2 Page 20. figure 10.1 figure 10 TM5820-398-35-C2-1 Figure 10.1.
Page 43, paragraph 36a, (page 8 of C 1) chart. Delete the last line and substitute: RF Millivoltmeter, Hewlett-Packard Model HP411A. Page 56, figure 31. Add the following note: Note. ON EQUIPMENT BEARING ORDER NO. 64009-PP-63, SWITCHES S2 AND S3 HAVE BEEN OMITTED. Page 60, paragraph 44, heading. After the heading, add the following note. Note. On equipment bearing Order No. 64009-PP-63, switches S2 and S3 are omitted.
Page 124, figure 61. Add figure 61.1 after figure 61: 4 Figure 61.1.
Page 151. Add chapter 6 after figure 79: CHAPTER 6 DEPOT INSPECTION STANDARDS 98. Applicability of Depot Inspection Standards The tests outlined in this chapter are designed to measure the performance and capability of a repaired Radio Set AN/PRC–2.5. Equipment that meets the minimum standards stated in the tests will furnish satisfactory operation, equivalent to that of new equipment. 99. Applicable References a. Repair Standards. Applicable procedures of the U.S.
Equipment Switch, tig~e, singl&pole, singl~throw ------------------------------------------------Barrier terminal biock, Cinch Jones type No. 2-172-Y (2 terminal) ----------------------Barrier terminal block, Cinch Jones type No. 8-172-Y (8 tirminak)----------------------Cable, coaxial, type RG-WA/U ------------------------------------------------------W&, strmded AWGNo.
Eguipmenf ,d?rd dock No. %%2 Capacitor, O.05pf +10To,4M vdc----------------------------------------------------- ------------Wire, stranded AWGNo. l8---------------------------------------------------------- 6145-160-5291 1 As required Lu~, spade ------------------------------------------------------------------------- ------------2 Test Cable No. 7 (fig. 79.3) consisting of: ------------4 Wire, stranded AWGNo.
Figure 79.2. Test cables No. 4, No.5, and No.6.
Figure 79.3. Test cables No. 7, No. 8, and No. 9.
Figure 79.4. Receiver dummy antenna, schematic and wiring diagrame.
Figure 79.5.
Figure 79.6. Test assembly, schematic/wiring diagram.
101. General Test Requirements Most of the tests will he performed under the conditions listed below and illustrated in figure 79.7 (for the receiver system tests) and in figure 79.8 (for the transmitter system tests). Testing will be simplified if preliminary standard control settings are made initially and changes from these settings are then made as required for the individual tests. Perform all tests in Enclosure, Electromagnetic Shielding MX-1761/C (or equivalent).
14 TAGO Figure 79.7.
103. Transmitter Test Setup (fig. 79.8) a. Plug the test assembly connector into POWER connector J3 on the front panel of the RT–505/ PRC-25. b. Connect a test cable No. 7 from ground of power supply A (2.5 volts) to terminal D of test assembly terminal board TB1. c. Connect a test cable No. 7 from the positive output of power supply A (2.5 volts) to terminal E of test assembly terminal board TB1. d. Connect a test cable No. 7 from ground of power supply B (12.
16 Figure 79.8.
723A/U (used as a vacuum-tube voltmeter) should be not greater than 0.02 volt. (7) Reestablish the standard receiver test conditions; use the HP-200AB to externally modulate the 1066A. (8) Without changing the RT-505/PRC-25 VOLUME control setting, determine the receiver audio output level produced with modulation frequencies of 300, 500, 2,000, and 3,000 cps (at 10-kc deviation). Acceptable frequency response is +0, – 6 db (from the 1,000-cps reference) at 300 cps, and +3, –6 db at 500,2,000, and 3,000 cps.
the space between module Al0 and the brass wheel-like part of the coupling. (3) Adjust RT-505/PRC-25 to a frequency 50-kc higher than its current setting. (4) Momentarily set the RT-505/PRC-25 function switch to OFF, then back to ON, and verify receiver audio output by observing the oscilloscope and the TS723A/U (used as a vacuum-tube voltmeter) indications. (5) Repeat the procedures given in (3) and (4) above until a frequency setting produces no audio output within 3 seconds, or until a frequency of 31.
(9) Repeat the procedures given in (7) and (8) above except increase the RF output 70 db to determine the 70-db-down points. The 70-db-down points should be less than 120-kc apart. (l0) Search 50 kc beyond the 70-db-down points for spurious responses. Detected spurious responses should not be above the -70-dblevel. Note. The receiver system tests are now completed. Perform the procedures indicated in paragraph 103 before proceeding. 105. Transmitter System Tests, Radio Set AN/PRC-25 a. Power Output Test.
(3) Record the RF and audiofrequencies being used and the deviation indicated on the ME-57/U. (4) Set the test assembly TRANSMITTER CARRIER switch to OFF. (5) Repeat the procedures given in (2), (3), and (4) above with modulation frequencies of 300, 2,000, and 3,000 cps. (6) Repeat the procedures given in (2), (3), and (4) above with the RT-505/PRC-25 set to 60.00 mc and modulation frequencies of 300, 1,000, 2,000, and 3,000 cps. (7) Evaluate the test results. At both 47.00 and 60.
Short Test frequency (mc) antenna loading Load characteristics — — — — - — — — — — Resistance (ohms) —————— — — 30.00-----------------52.50-----------------53.50-----------------75.00------------------ Capacitancee (uff) (7) Minimum voltage (rms) — — ————— 26.1 56.2 56.2 61.9 12 18 18 82 4 7 5 7 (11) Set the test assembly TRANSMITTER CARRIER switch to ON and read the RF voltage across the resistor of the transmitter load with the ME-26B/U.
106. Miscellaneous System Tests and Inspection, Radio Set AN/PRC-25 a. Tests. (1) Perform the miscellaneous system tests with the equipment connected in a standard transmitter test setup (para 103 and fig. 79.8) . (2) Connect Handset H-138/U to one of the AUDIO connectors on the front panel of RT-505/PRC-25. (3) Press the H-138/U keying button and speak into the microphone. The AN/ URM-43A; ME-57/U, and AN/USM-50A should indicate transmitter output, and sidetone should be heard from the earphone.
By Order of the Secretary of the Army: HAROLD K. JOHNSON, General, United States Army, Chief of Staff. official: J. C. LAMBERT, Major General, United States Amy, The Adjutant General.
TM 11-5820-398-35 Technical Manual No. 11-5820-398-35 HEADQUARTERS, DEPARTMENT OF THE ARMY WASHINGTON 25, D. C., 8 January 1963 RADIO SET AN/PRC-25 Paragraph Page 1,2 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 THEORY 4,5 3-5 Block diagram analysis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-40 6-33 Circuit analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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CHAPTER 1 INTRODUCTION 1. Scope a. This manual covers field and depot maintenance for Radio Set AN/PRC-25. It includes instructions appropriate to third, fourth, and fifth echelons for troubleshooting, testing, aligning, and repairing the equipment. Detailed functions of the equipment are covered in the theory chapter. b. The complete set of technical manuals for this equipment includes TM 11-5820398-10, TM 11-5820-398-20, TM 11-5820398-20P, and TM 11-5820-398-35P. c.
CHAPTER 2 THEORY Section I. BLOCK DIAGRAM ANALYSIS 3. Receiving Signal Path (fig. 82) Receiver-Transmitter, Radio RT-505/ PRC-25 is tunable in 50-kilocycle (kc) increments over a frequency range of 30.00 to 75.95 megacycles (me) to provide 920 channels. The frequency range is covered in two bands: the low band is 30.00 to 52.95 mc; the high band is 53.00 to 75.95 mc. The front panel tuning controls and the BAND switch are used for tuning the RT-505/PRC-25 to the desired frequency. a.
f. The receiver audio amplifier output, including the 150-cps tone, is applied to the squelch input amplifier. The squelch input amplifier with the emitter -follower and squelch feedback amplifier passes the 150-cps tone, which is rectified in the squelch direct current (dc) detector amplifier. When the squelch relay driver receives a signal from the dc detector amplifier, it provides the current necessary to energize K3.
those used for transmission, unless otherwise indicated, by subtraction of 50 kc from the given frequency. a. The vfo output frequency ranges from 41.50 mc to 64.45 mc. The specific frequency depends on the channel selected, and whether the channel is in the high or low band. (1) When the low band is used, the vfo operates at 11.50 mc above the carrier frequency. For example, at a received frequency of 33.10 mc, the vfo frequency is 44.60 mc. (2) When the high band is used, the vfo operates at 11.
also has an input from the 50-kc interval oscillator. g. The- 50-kc interval oscillator generates one of three frequencies: 5.55 mc, 5.60 mc, or 5.65 mc. The specific frequency depends on the frequency selected by the kc tunin g knob (50- or 100-kc increments) and whether the RT-505/PRC25 is receiving or transmitting. When a 50-kc channel point (37 .45, 71.25, etc) is selected, the 50-kc interval oscillator output frequency will be 5.60 mc during reception.
(2) High band. Transformer T3, fixed capacitor C11, trimmer capacitor C9, and tuning capacitor C2C make up the tuned circuit. Switch S1-D shorts the low-band tuned circuit to prevent loss of energy when operating on the high band. c. The combinatoin of resistors R3 and R2 establishes the fixed bias for transis tor Q1. Resistor R1 is the emitter swamping resistor. Capacitor C6 and resistor R4 form a parasitic suppressor. Inductor L2 is an rf decoupling coil.
Figure 1.
10 Figure 2.
the tuned circuit consisting of capacitor C9 and the primary winding of transformer T1. (2) The combination of resistors R2 and R3, R7 and R8, and R11 and R12 develops base-to-emitter bias for Q1, Q2, and Q3 respectively. Resistors R4, R9, and R13 are emitter swamping resistors. Capacitors C3, C6, and C8 are emitter rf bypass capacitors for Ql, Q2, and Q3 respectively. Resistors R5 and R10 are collector load resistors for amplifiers Q1 and Q2, respectively.
tively. Resistors R17 and R21 are collector load resistors for Q4 and Q5, respectively. c. Receiver Discriminator Driver Q6. The receiver discriminator driver amplifies and limits the 11.5-mc if. signal output from Q5 and applies a strong signal of constant amplitude to discriminator Z1 (fig. 88). (1) The 11.5-mc signal from Q5 is coupled through capacitor C15 to the base of Q6.
Figure 4. Receiver audio amplifier module A25, schematic diagram. lower Q2 have a common emitter resistor, R6. Transistor Q2 operates near saturation. Audio input signals from the audio amplifier module are applied through isolation resistor R2, attenuated by dropping resistor R3, and are applied, through coupling capacitor C2 to input amplifier Q1. The audio output signals from Q1 are developed across collector load resistor R7 and directly coupled to the base of squelch feedback amplifier Q3.
cycles of the 150-cps signal will cause the amplifier-detector to conduct. The output developed across collector load resistor R18 is a negative-going half-wave rectified s i g n a 1. The output signal is filtered by capacitor C9 and is directly coupled to the base of relay driver Q5. The negative dc signal causes transistor Q5 to conduct, which causes current to flow through the squelch relay winding. When relay K3 energizes, the receiver circuits will operate. c.
coupling capacitor C7 to the base of output limiter Q3. The output limiter signal is developed across collector load resistors R17 and R18. The audio output to A20 (para 14) of the sso is coupled through capacitor C10 while the sidetone output to receiver audio module A25 is directly coupled from the junction of resistors R17 and R18. A 150-cps tone signal from the tone generator module is superimposed on the audio output signal to the sso through isolation resistor R19. b.
13. Tone Generator Module A23 (fig. 7) The tone oscillator functions only during transmission. The 150-cps output tone is applied to the speech amplifier limiter module (para 12) which frequency-modulates the transmitter output carrier signal with the tone at all times during transmission. The 150-cps tone disables the squelch circuit in the distant receiver. a. During transmission, +10-volt dc operating voltage is applied to transistor Q1 which oscillates at 150-cps.
network contributes a stability f actor about 40 times greater than that of a free-running oscillator. a. Sidestep Oscillator Module. (1) The audio signal from speech amplifier limiter module A22 (para 12) is coupled to the sso through coupling capacitor C6 and isolating resistors R8 and R7, across diode CR1. Diode CR1 is a variable capacitance diode. When the audio signal is applied across the diode, the effective capacitance of CR1 changes as the voltage across it varies.
Figure 8. Sidestep oscillator module A20, schematic diagram. isolation, and proper match for the vfo signal applied to the fss. An output from the vfo is directly fed to receiver mixer A5 (para 8) and heterodyned with the incoming signals to produce the 11.5-mc if. The third vfo output is applied to transmitter mixer Q2. a. VFO Q1. (1) Collector-to-emitter fee db a c k through capacitor C2 and inductor T1 maintains oscillation in Q1.
Figure 9. Quarter-wave network module A19, schematic diagram. emitter. Inductor L3 and capacitor C13 form a filter network to prevent rf leakage into the power supply. c. Transmitter Mixer Q2. (1) The transmitter mixer functions only during transmission. The sso input from A20 (para 14) is applied through isolation resistors R8 and R16 and coupling capacitor C3 to the base of Q2. The vfo output is applied through isolating resistors R10 and R16 and coupling capacitor C3 to the base of Q2.
20 Figure 10.
Figure 11.
decreasing the total capacitance. The rf input to module A8 can be measured at test jack J2. d. Inductor L2 and capacitors C6 and C7 (in the main frame (fig. 88)) form a filter in the +10-volt regulated input to module A8. 17. Transmitter Second Rf Amplifier Module A7 (fig. 12) Transmitter second rf amplifier module A7 amplifies the signal from transmitter first rf amplifier module A8 (para 16). Module A7 consists of a single transistor amplifier, a BAND switch, and a tuned output circuit. a.
c. Capacitors C2 and C3 and inductor L1 prevent rf variations from reaching the -45-volt dc supply. The combination of resistors R2 and R3 provides fixed bias, and resistor R1 is the emitter swamping resistor Q1. Inductors L2 and L3 are rf chokes. Capacitor C7 is inserted into the high-band output tank circuit by S1C to shift the effective range of ganged tuning capacitor C1B by decreasing the total capacitance. The rf input to module A7 can be measured at test jack J2. d.
Figure 13. Transmitter ipa module A6, schematic diagram. the -45-volt supply. A pi-type filter consisting of capacitors C2 and C5 and inductor L2 prevents rf variations on the filament of tube V2 and rf leakage into the 2.5-volt filament supply. The combination of plate inductor L3 and bypass capacitor C4 prevents rf leakage into the +125-volt power supply. Resistor R3 is a screengrid voltage dropping resistor; capacitor C3 is the screen-grid bypass capacitor. 20. Power Amplifier Tank Module A2 (fig.
Figure 14. Power amplifier A29, schematic diagram. L1 (low band) or capacitor C4 (high band) through switch SIB, through pin 3 of 2AJ1 and pin 9 of J7 to receiver first rf amplifier module A3. c. On the low-band tuned circuit, the slug in transformer T1 is an alignment adjustment for the low frequency end, while capacitor C1 is an alignment adjustment for the high frequency end.
Figure 15. Power amplifier tank module A2, schematic diagram. c. The tuning controls tune inductors L1, L2, and L3, which are in series with capacitors C2, C1, and C3, respectively, to resonate the antenna in the low and high bands. When the BAND switch is in the low position, inductor L3 and capacitor C3 are placed in the circuit; when the BAND switch is in the high position, inductors L1 and L2 and capacitors C2 and Cl are placed in the circuit. 22.
Figure 16. Antenna loading network A28, schematic d i a g r a m , Figure 17. First mixer module A14, schematic diagram.
ing of diode CR3, capacitor C5, and resistor R8, to the center tap of the primary of transformer T2. It is terminated in a tuned network consisting of capacitor C4, inductor L1, and resistor R7. The network is broadly tuned to 7 mc. The spectrum generator output contains the 1st through the 12th harmonic of the fundamental 1-mc pulse.
Figure 18. 1-mc spectrum generator module A15, schematic diagram. C10 to the selected crystal ((2) below), and the contacts of S1A to the emitter of Q2; this action completes the regenerative circuit. (2) Crystal selection is determined by the operating mode (received or transmit) and by the frequency selected by the kc tuning control. When the RT-505/PRC-25 is in the receive mode, +10 volts is applied through normally closed contacts 4 and 6 of front-end relay K1 (fig.
and A10J1 and current-limiting resistor R7 to the anode of CM. This positive voltage forward biases CR2; the diode conducts heavily and allows the regenerative circuit to crystals Y13 and Y14 to be completed. If the RT-505/PRC-25 is operating on a 100-kc channel (31.0 mc, 74.20 mc, etc), S1A will be in the position shown and crystal Y13 (5.60 mc) will be selected through contacts 8 and 11 of S1A to complete the regenerative circuit to the emitter of Q2.
Figure 19.
Figure 20. 53-Mc filter module A 13, sthematic diagram the filter properly and minimize variations due to the varying impedances of transistors. The rf output of module A12 can be measured at test jack J2. 27. Frequency Synthesizer System If. Amplifier Module A18 (fig. 22) The fss if. amplifier module (A18) amplifies the 5.6-mc signal input from fss second mixer module A12 (para 26) and applies it to fss discriminator driver module All (para 29) and phase comparator module (para 28) A17. The fss if.
Figure 21. Second mixer module A12, schematic diagram. output termination and minimizes variations due to discriminator loading. The combination of resis-. tor R9 and capacitor C11 prevents rf leakage into the +10-volt dc supply. (3) The rf output of module A18 can be measured at test jack J2. 28. Phase Comparator Module A17 (fig. 23) Phase comparator module A17 contains phase comparator driver Q1 and the phase comparator. The phase comparator compares the phase of the signals from f ss if.
Figure 22. Speech amplifier limiter module A18, schematic diagram. transformer T1. Resistors R1 and R2 form a voltage divider which provides the fixedbias portion of the emitter-to-base bias. Emitter resistor R3 establishes the fixed portion of the emitter-to-base bias and stabilizes the emitter current. Capacitor C2 is a bypass capacitor for the Q1 emitter. Capacitors C5 and C6 and inductor L1 form a pi-filter which prevents any rf signals from entering the 10-volt dc Supply b. Phase Comparator.
Figure 23. Phase comparator module A17, schematic diagram. since E1 and E2 voltages are exactly 180° out-of -phase. (4) If the vfo frequency increases or decreases, changing the 5.6-mc input signal, the 90° vector relationship between the E1 and E2 signal and the E3 signal no longer exists. The change in frequency is equivalent to an E1-E2 phase shift with respect to E3.
apc voltage in its output circuit. The two input signals are the fss if. signal from the fss if. amplifier module A18 (para 27) and a dc voltage from phase comparator module A17 (para 28). The apc voltage is applied to the capacitance diode circuit of the vfo. If aphase-locked condition exists (that is, if the vfo is on frequency), the apc voltage will assume the reference level to maintain the vfo output on frequency.
Figure 24. Fss discriminator module A11, schematic diagram. maintains a constant voltage drop. When the output voltage increases due to a decrease in load or an increase in the input voltage, a proportional positive voltage increase appears at the emitter of dc amplifier Q2 and results in more current flow through Q2. The base of series regulator Q1 goes more positive; conduction through Q1 decreases, which effectively increases the impedance of series regulator Q1.
Figure 25. Voltage regulator module A16, schematic diagram. condition induces a voltage in the feedback winding of transformer T1. The voltzage is applied to the bases of the transistors, causing Q1 to conduct even more, and driving Q2 further into cutoff. The flux in the core of transformer T1 changes at a nearly constant rate until the core is saturated. When saturation occurs, no voltage is developed in the feedback windings of transformer T1.
used in conjunction with Test Set, Electronic Plug-in Circuit AN/GRM-55 to isolate a faulty module at the organizational level. If usedproperly, however, the signal voltages at these test points will expedite maintenance effort at higher echelons. A listing of the modules which are equipped with test points and a description of the signal to be expected at the test point are given below. a. Module A1. Module A1 has two test points: J2 and J3.
the output of oscillator Q1 (in A10) to be checked. A typical rf signal level at this test point is 0.2 volt. Test point J3 permits the output of oscillator Q2 (in A10) to be checked. A typical rf signal level at this test point is 1.8 volts. j. Module A11. Module All has one test point: J2. Test point J2 permits the output of the discriminator (in A11) to be checked. A typical discriminator output level, with the fss if. input disabled (by pressing S2 on the main frame), is a l.
the 0A-3633/GRC. The power distribution when a BA-386/PRC-25 is used is similar except that a shorting cap is installed on J3 and the BA-386/PRC-25 is connected to J4 (fig. 88). b. Receive (fig. 86). When function switch S1 is at ON, and the handset pushto-talk button is not depressed, the RT 505/PRC-25 will receive. The input voltage from the primary power source is applied through connector J3. (1) The input voltage from connector J3E (+12.5 volts) is connected to contact 2 of S1 (rear). The +12.
CHAPTER 3 THIRD ECHELON MAINTENANCE Section I. GENERAL TROUBLESHOOTING TECHNIQUES Warning: Be extremely careful when servicing the RT-505/PRC-25. During operation, 125 volts dc exists at the plate circuit of the power amplifier. 34. Scope of Third Echelon Maintenance Third echelon maintenance procedures (para 35 through 45) supplement the maintenance procedures described in TM 115820-398-10 and TM 11-5820-398-20.
PRC-25. The charts also list the associated technical manuals for the equipment. a. Test Equipment. ‘hat equipment Technical manual Multimeter ME-26 B/U --R;3tV#meter AN/URM- TM 11-6625-200-12 TM 11-5133 S~&$;~ratar AN/ TM 11-1257 Frequency Meter AN/ USM-26. RF Millivoltmeter 411A TM 11-5057 aIf specific models are not available, other models of tbe same nomenclature having eimilar oharacteris tics may be used. b. Additional Equipment Required.
Figure 28. Typical alignment cover for module A20. Section II. THIRD ECHELON TROUBLESHOOTING Caution: Do not attempt removal or replacement of parts before reading the instructions in paragraph 40. 37. Test Setup a. Preparatory Steps. Prepare the RT505/PRC-25 for bench testing as follows: (1) Remove Battery Box CY-2562/ PRC-25 and Battery, Dry BA-386/ PRC-25 (TM 11-5820-398-10 (para 28)). (2) Remove the receiver-transmitter case (TM 11-5820-398-20 (para 8)).
(d) S e t t h e r e c e i v e r - t r a n s m i t t e r controls as follows: (d) Connect Handset H-138/U to one of the receiver-transmitter AUDIO connectors.
Item e. Defective relay K3 or relay socket XK3 . f. Defective wiring between XK3 and A2’7. g. Defective capacitor A27C1O or A27C11. 3 Received signals are not heard, but a rushing noise is heard fn the H-138/U when the function switch is at ON and the long antenna is fnstalled at ANT connector J1. Received signals are normal with the short antenna installed. a. Defective A28S2 or A28S3 ---- b. Defective A28S1 or A38L4 --- c. Defective A28S1, A281.A, or A28C2.
Item Indication Probable trouble either band when the hmction switch is at ON. Transmit operation is normal. b. Be fective A30L2 ------------c. Defective wiring in the regulated +10-vol~line to A3_, A4, A5, or A21. d. Defective wiring between A2 and A3 . e. Defective wiring between A3 and A4. f. Defective wiring between A4 and A5. L?. Defective wiring between A9 and A5. h. Defective wiring between A5 and 11. 5-me filter FL3. i. Defective 110 5-me fflter FL3- J Defective wiring between FL3 and A21.
Item indication in the H-138/U with. the iimction switch at SQUELCH. 9 b output ia heard in the H-138/U when the function switch ia at SQUELCH in either the receim or tranamit mcde of operation. 10 To output ie heard in the H-138/U when tlw function switch is at SQUELCH with a proper (150CPS modulated) signal being received. No out@ is heard in the H-138/U during transmit operation when the function switch is at SQUELCH. Output is normal during receive operation.
Item Indication 13 Receives signal on the wrong channel. Transmit operation is normal. 14 High-frequency noise in the audio output. Tuning knobs do not function properly. 15 Probable trouble Procedure E of J19. Ch6ck physical condition of J19 (fig. 31 and 88). d. Defective wiring between A15 d. Check continuity between pin E and A14. of J21 and pin F of J20. Check physical condition of J21 (fig. 31 and 88). e. Defective wiring between A13 e. Check continuity between pin J and A1O.
Item 3 4 Indication o rf Power output indicated on the AN/URM-43A on one band. Receiver operation ia normal on both bands. o rf power output indicated on the AN/URM-43A on either band. R& ceive operation is normal. Probable trouble i. Defeotive C 1 ---------------- R. >. Defeotive S4, or wiring from S4 to A26 assembly. b. >. Defeotive wiring between A19 and A20. c. i. Defeotive FL1 or FL2 -------- R. ). Defeotive A30L2 ------------ b. >. Defeotive relay K1 ------—-- c. i.
Item Indication Probable trouble 1. Defective wiring between A26 and A20. n. Defective wiring between A20 and A9. n. Defective wiring between A9 ant A8. o. Defective wiring between A8 anc A’7. p. Defective wiring between AT anc A6. q. Defective wiring between A6 anc A29. r. Defective C3 and C4 ---.----s. Defective components in A29 -- 5 6 7 ?ranamits and receives signals on wrong channel on either band. ?ranamits signal on wrong channel on either band.” Receiver operation is normal.
Item 13 14 15 16 Indication is at SQUELCH. Receiver operation is normal. Transmits a modulated carrier that cannot be received when an RT-505/PRC-25 at the receiving site is in the SQUELCH mode of operation, Sidetone is heard in H-138/U. Same as step 13 except no sidetone is heard in H-138/U. BAND switch does not function properly. Tuning knobs do not function properly. Probable trouble Defective wiring between A23 and A22. Check continuity between pin 1 A23J2 and pin 4 of A22J2 (fig. 33 and 88).
Figure 29. Transmitter power amplifier test points and parts location. Section III. THIRD ECHELON REPAIRS 40. Scope of Third Echelon Repairs a. The third echelon repairman may remove and replace audio and control chassis A27, the synthesizer mother board A26, and all other components within the RT505/PRC-25. b. Paragraphs 41 and 42 contain instructions for removing and replacing parts of the RT-505/PRC-25.
41. Removal and Replacement of Audio and Control Chassis A27 (fig. 32) a. Removal. (1) Remove modules A21 through A25 as described in TM 11-5820-39820, paragraph 10a. (2) Remove relay K3. (3) Unsolder and remove 11.5-mc filter FL3. (4) Unsolder and remove receiver discriminator Z1. (5) Tag and unsolder all wiring to relay socket XK3 and audio and control chassis A27 terminal strip. (6) Rem o v e the wiring through the grommet at the lower left corner of the audio and control chassis.
Figure 30. Receiver-Transmitter, Radio RT-505/PRC-25, bottom view.
Figure 31. Receiver-Transmitter, Radio RT-505/PRC-25, bottom view, modules r e m o v e d .
Figure 32. Receiver-Transmitter, Radio RT-505/PRC-25, top view.
TM 5820-398-35-31 Figure 33. Receiver-Transmitter, Radio RT-505/PRC-25, top view, modules removed.
Figure 34. Receiver-Transmitter, Radio RT-505/PRC-25, top view, audio and control chassis A27 open. Section IV. THIRD ECHELON ALIGNMENT Note: Third echelon alignment consists of aligning transmitter power amplifierTank module A2, variable frequency oscillator module A9, and sidestep oscillator module A20. 43. Alignment of Power Amplifier Tank Module A2 (fig. 30 and 31) a. Set the rf output of the AN/URM-48 for 30.00 mc, modulated ±10 kc by a 1,000 cycle-per-second (cps) tone. b.
j. Set the rf output of the AN/URM-48 for 53.00 mc, modulated ±10 kc by a 1,000cps tone. k. Set the BAND switch of the receivertransmitter at 53-75, and the tuning controls for 53.00 mc. 1. Adjust A2T2 for a maximum indication on the ME-26B/U. m. Set the rf output of the AN/URM-48 for 75.95 mc, modulated ±10 kc by a 1,000cps tone. n. Set the receiver-transmitter tuning controls for 75.95 mc. o. Adjust A2C2 for a maximum indication on the ME-26B/U. p.
CHAPTER 4 FOURTH ECHELON MAINTENANCE Section I. FOURTH ECHELON REPAIRS 46. Scope of Fourth Echelon Repairs Fourth echelon maintenance includes those functions allocated to third echelon maintenance (ch 3). In addition, it also includes removal and replacement of the front panel and the selector mechanism housing assembly, and alignment of tuning capacitors C1 and C2. (11) (12) (13) 47. Removal and Replacement of Front Panel a. Removal. (1) Remove modules A2, A6, A 10, and A16.
secure the selector mechanism housing assembly to the chassis. (6) Replace tuning capacitors C1 and C2 and secure them with four screws. Note: Do not tighten the clamp on the shaft of tuning capacitors C1 and C2 at this time. (7) Replace the relay socket assembly on the spacer legs and secure it with screws. (8) Replace the clamps that secure the electrical leads to the selector mechanism housing assembly. (9) Solder the shield and center conductor to ANT connector J2.
Figure 36. Receiver-Transmitter, Radio RT-505/PRC-25, top view, audio and control c h a s s i s o p e n . Figure 37. Receiver-Transmitter, Radio RT-505/PRC-25, front panel, tuning knobs removed.
and secure it with the three audio a n d c o n t r o l c h a s s i s captive screws. 48. Removal and Replacement of Selector Mechanism (fig. 37, 38, and 40) a. Removal. (1) Remove the front panel (para 47). (2) Remove the receiver-transmitter tuning knobs as follows (fig. 40): Note: Removal of the mc and the kc tuning knob assemblies from their respective shafts is identical. Removal of the kc stop assembly can be accomplished without disassembling the kc tuning knob assembly.
Figure 38. Front panel, rear view. Figure 39. Tuning capacitor assembly.
Figure 40. Tuning knob assembly. Section II. FOURTH ECHELON ALIGNMENT 49. General a. Scope of Fourth Eohelon Alignment Procedures. Fourth echelon alignment consists of aligning tuning capacitors C1 and C2. These capacitors must be aligned whenever the front panel is replaced, or whenever tuning capacitor C1 or C2 is replaced. b. Equipment Required. A Ballantine Direct Capacity Meter Model 520 or equivalent is required. 50. Tuning Capacitor C1 Alignment (fig.
rotation curve by turning C1 counterclockwise (from shaft end) and noting that the 520 indicates a decrease in capacity. Reset to 68 microfarads (uuf). f. Tighten clamp on the Cl tuning shaft. g. Adjust the RT-505/PRC-25 tuning knobs to 52.95. The 520 should indicate 10 uuf, or a difference of 58 uuf from the 30.00 mc indication (e above). h. If a difference of approximately 58 uuf is not obtained, repeat the procedure given in b through g above. i. Replace module A8 in the chassis. 51.
nections or test indications that may differ from those given in the test procedures. (2) Unless otherwise specified, all tests are to be performed with the RT-505/PRC-25 connected to Battery, Dry BA-386/PRC-25. (3) The electrical tests should be conducted in a screen room. If available, use Inclosure, Electromagnetic Shielding MX-1761/G or its equivalent. c. Test Equipment. Technical manual Nomenclature I Audio Oscillator TS382F/U. Voltmeter, Meter ME-30A/U Frequency Me@ AN/USM26.
55.
70 Figure 42.
56.
72 Figure 43.
57.
74 Figure 44.
58.
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78 Figure 45.
59.
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Figure 46.
60.
84 Figure 47.
61.
86 Figure 48.
62.
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90 Figure 49.
63.
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94 Figure 50.
64.
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98 Figure 51.
65.
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102 Figure 52.
66.
67. Summary of Test Data Personnel may find it convenient to arrange the checklist in a manner similar to that shown below. 8. RECEIVER Performance Performance standard CATCHING RANGE a. 31.50 Test data Test Test data Test 300 mc kc minimum deviation standard and above below 31.50 m c . 1. TRANSMITTER POWER b. 5 1 . 5 0 300 mc OUTPUT 30.00 mc 2 watts minimum and b. 4 2 . 0 0 mc 2 watts minimum m c . watts minimum a. 52.95 mc 2 d. 5 3 . 0 0 mc 1.
CHAPTER 5 FIFTH ECHELON MAINTENANCE 68. Scope of Fifth Echelon Maintenance The functions allocated to fifth echelon maintenance level include troubleshooting, repair, and alignment of modular assemblies. Also included is replacement of parts in the selector mechanism assembly and in module A10. 69. Test Equipment and Additional Equipment Required a. Test Equipment.
(2) Connect the handset to either AUDIO connector. b. Performance Test. (1) Press the handset push-to-talk switch. (2) Set the ME-26 B/U to the 300-volt, dc range. Normal indication at J3 is +125 volts; normal indication at J2 is -45 volts dc. c. Faulty Part Isolation. Note: Make all measurements with respect to ground unless otherwise specified. (1) Measure the dc resistances at the points listed below and compare them with the normal resistances.
Figure 53. Module A1 parts location.
procedure given in (9) above should be 1,100 kc. (12) Change the receiver-transmitter BAND switch to 53-75. (13) Adjust the AN/URM-48 frequency to 53.000 mc as indicated by the AN/USM-26. (14) Repeat the procedures given in (1) through (9) above. The input-tooutput voltage ratio noted in (3) above should be +1 db; the 3-db bandwidth computed in the procedure given in (9) above should be 3,300 kc. (15) Adjust the AN/URM-48 frequency to 75.950 mc as indicated by the AN/USM-26.
Figure 54. Module A2 parts location. diagrams and to figures 55 and 56 for test points and parts location. a.Preparation. (1) Prepare the following equipment: (a) Signal Generator AN/URM-48. (b) Frequency Meter AN/USM-26. (c) Rf Millivoltmeter 411A. (d) Adapter UG-274B/U. (e) Multimeter ME-26B/U. (2) Connect the AN/URM-48 output to a male connector of the UG-274B/ u. (3) Connect the AN/USM-26 to the other male connector of the UG274B/U.
noted in (3) above. Record the frequency. (9) Increase the AN/URM-48 frequency until the output level indicated by the 411A is again at the level noted in (3) above. Record the frequency. (10) Compute the difference between the frequencies noted in (8) and (9) above. The frequency difference is the 6-db bandwidth, which should be 700 kc. (11) Repeat the procedures given in (1) through (10) above for A3 at 52.95 mc, 53.00 mc, and 75.95 mc.
indication cannot be increased by tuning. (11) Remove the shorting jumper from pins E and H of J9. (12) Replace A5. 74. Isolating Trouble in Module AS (fig. 3 and 57) a. Preparation. (1) Prepare the following equipment: (a) Signal Generator AN/URM-48. (b) Frequency Meter AN/USM-26. (c) Rf Millivoltmeter 411A. (d) Adapter UG-274B/U. (e) Multimeter ME-26B/U. (2) Connect the AN/URM-48 output to a male connector of the UG-274B/ U. (3) Connect the AN/USM-26 to the other male connector of the UG274B/U.
Figure 56. Module Ad parts location. (9) Increase the AN/URM-48 frequency until the level indicated by the 411A is again at the level noted in (5) above. Record the frequency. (10) Compute the difference between the frequencies noted in (8) and (9) above. The frequency difference is the 6-db bandwidth, which should be at least 32 kc. (11) Perform the procedures given in (1) through (10) above for 75.95 mc, except that normal gain in (4) above is 0 db.
receiver-transmitter front panel controls as follows: (1) Turn the BAND switch to 30-52. (2) Turn the tuning knobs to 30.00 mc. (3) Turn the function switch to ON. e. Alignment Procedure. (1) Adjust the AN/URM-48 frequency to 30.000 mc and adjust the output for 10 millivolts between pins A and B of A5J1. (2) Connect the 411A between A21J3 and chassis ground. (3) Adjust A5T2 for a peak indication on the 411A. (4) Disconnect all connections. (5) Replace the module cover. 75.
frequency difference is the 3-db bandwidth, which should be 1,200 kc. (11) Adjust the AN/URM-48 frequency to 52.95 mc as indicated by the AN/ USM-26. (12) Repeat the procedure given in (1) through (10) above; return the AN/ URM-48 to 52.95 mc noted in (6) and (9) above. (13) The gain noted in (3) above should be +21 db; the 3-db bandwidth computed in the procedure given in (10) above should be 900 kc. (14) Change the receiver-transmitter BAND switch to 53-75. (15) Adjust the AN/URM-48 frequency to 53.
(9) Repeat the procedures given in (1) through (8) above until the 411A indication cannot be increased by tuning. (lo) Set the BAND switch on the receiver-transmitter at 53-75, and the tuning knobs at 53.00 mc. (11) Disconnect the 411A from J1S1 and connect it across the AN/URM-48 output. (12) Adjust the AN/URM-48 frequency to 53.00 mc and the level to 100 millivolts, as indicated by the 411A. (13) Disconnect the 411A from the AN/ URM-48 and connect it between pins 1 and 2 of S1J1.
(2) Connect the 411A across the AN/ URM-48 output. Press the push-totalk switch. Adjust the AN/URM-48 for a 100-millivolt indication on the 411A. (Note the db indication.) (3) Disconnect the 411A from the AN/ URM-48 and connect it between pins 3 and 4 of J1. The 411A should indicate 16 db more than the value indicated in (2) above. (This value, +16 db, is the stage gain.) (4) Adjust the AN/URM-48 level to obtain a 0-db indication on the 411A.
(2) After the replacement of a faulty part, perform the alignment procedures given in d and e below, and repeat the procedures in a and b above. d. Preparation fix Alignment. (1) Set the receiver-transmitter front panel controls as follows: (a) BAND switch at 30-52. (b) Function switch at ON. (2) Connect the AN/URM-43A to ANT connector J2. (3) Connect the H-138/U to an AUDIO connector. (4) Remove module A8. (5) Connect the AN/URM-48 between pins 1 and 2 of A7J1. e. Alignment Procedure.
Figure 59. Module A7, parts location. (5) (6) (7) (8) (9) (lo) (11) (12) tain a O-db indication on the 411A. Increase the AN/URM-48 frequency until the 411A indicates a 3-db decrease. Connect the AN/URM-48to the AN/ USM-26 and record the frequency. Decrease the AN/URM-48 to 30.00 mc. Connect the AN/URM-48 between pins 1 and 2 of A8J1. Decrease frequency of the AN/ URM-48 until the 411A indicates a 3-db decrease. Connect the AN/URM-48 to the AN/ USM-26 and record the frequency.
(22) If the gain and bandwidth do not meet the standards of the procedure, proceed to c below. c. Faulty Parts Isolation. (1) Remove module A9. Connect the H138/U to an AUDIO connector. Apply a 30.00 mc, 100-millivolt signal between pins 1 and 2 of A8J1. Press the push-to-talk switch. Measure the voltages at the points given in the charts in (a) and (b) below. Compare them with the normal signal and dc voltages listed. Note: Measure all voltages to ground. (4) (5) (6) (7) (8) (a) Signal voltage chart.
Figure 60. Module A8, parts location. Connect the ME-26B/U to A9J3. Connect the 411A to A9J4. Set the receiver-transmitter front panel controls as follows: (a) BAND switch at 30-52. (b) Tuning knobs for 30.50 mc. (c) Function switch at ON. b. Vfo Frequency Test. (1) While - rotating the mc tuning knob in 1-mc increments from 30.50 to 52.50 mc, observe the indications on the ME-26B/U, the AN/USM-26, and the 411A. (2) A normal apc voltage indicated throughout the tuning range by the ME-26B/U is +3.
(9) Disconnect the 411A from J20. Replace A14. Connect the 411A to A9J4. (10) S e t t h e r e c e i v e r - t r a n s m i t t e r BAND switch to 53-75. (11) While rotating the receiver-transmitter mc tuning knob in l-mc increments from 53.50 to 75.50 mc, observe the indications on the ME26B/U and the 411A. (12) The ME-26B/U indication should be the same as that in (2) above; the 411A indication should be the same as that in (4) above.
50 kc, as indicated by the AN/USM26. (15) If the frequency difference given in (11) above is greater than that given in (7) above, adjust C8 counterclockwise until the vfo frequency is increased by 50 kc, as indicated by the AN/USM-26. Adjust C9 clockwise until the vfo frequency is returned to its nominal value, 63.000 mc, as indicated by the AN/USM-26. (16) Repeat the procedures given in (1) through (11) above.
Figure 61. Module A9, parts location. (5) (6) (7) (8) (9) (10) 124 47.050; the 411A should indicate 0.2 volt. Set the tuning knobs for 30.30 mc. The AN/USM-26 should indicate 47.150 mc; the 411A should indicate 0.2 volt. Set the tuning knobs for 30.40 me. The AN/USM-26 should indicate 47.250 mc; the 411A should indicate 0.2 volt. Set the tuning knobs for 30.50 mco The AN/USM-26 should indicate 47.350 mc; the 411A should indicate 0.2 volt. Set the tuning knobs for 30.60 mc.
A10J3 ana reconnect the AN/USM26. The AN/USM-26 should indicate 5.6000 mc. (7) Connect the H-138/U to an AUDIO connector and press the push-totalk switch. The AN/USM-26 should indicate 5.5500 mc. (8) Set the tuning knobs for 30.00 mc and press the push-to-talk switch. The AN/USM-26 should indicate 5.6000 mc. (9) Disconnect the AN/USM-26 from A10J3 and reconnect the 411A. Press the push-to-talk switch. The 411A should indicate 1.8 volts rms. (10) Set the tuning knobs for 30.
Figure 62. Module A10, parts location. (3) Turn the receiver-transmitter function switch to ON. b. Dc output Level Test. (1) Connect the AN/URM-48 between A18J2 and chassis ground. Connect the AN/USM-26 and the 411A across the AN/URM-48 output. (2) Press S2 (fig. 31) and adjust the AN/URM-48 frequency to the level to 0.2-volt as indicated by the 411A. (3) Disconnect the 411A from the AN/ URM-48 and connect it between pin F of A11J1 and ground. (4) Connect the ME-26B/U between A11J2 and chassis ground.
(2) Adjust transformer T1 for a maximum dc indication on the ME-26B/ U. (3) Set the output of the AN/URM-48 to 5.20 mc. (4) Adjust transformer T2 for a minimum indication on the ME-26B/U. (5) Set the output of the AN/URM-48 to 5.60 mc. Adjust T1 until the ME-26B/U indicates +2.8 volts dc. (6) Replace module A12. 81. Isolating Trouble in Module A12 (fig. 21 and 64) a. Preparation. (1) Prepare the following equipment: (a) Rf Millivoltmeter 411A. (b) R. F. Signal Generator AN/URM25F.
(a) Signal voltage chart. Volts (rma ) Point of measurement ---------------------------~ (2) 0.008 0.0 0.80 0.10 (b) Dc voltage chart. (3) Point of measurement Voltage (dc ) J1-D --------------------- ----Q1 bsse -----------------------Q1 colleotor ------------------Q1 emitter --------------------- 10.0 4.2 0.0 4.5 (2) After the replacement of a faulty part, perform the alignment produres given in paragraph 86 and repeat the procedures given in a, b, and c above. Replace module A13.
procedure given in (8) above differs from that indicated in (5) above by more than 2 db, proceed to the alignment procedures in c below. (10) If the indications obtained in the procedure given in (5) and (8) above are normal, testing of A13 is completed. c. Faulty Parts Isolation. Insert the module extender (fig. 27) into the A13 con- nector on the mother board. Insert A13 into the module extender.
83. Isolating Trouble in Module A14 (fig. 17 and 66) a. Preparation. (1) Prepare the following equipment: (a) Signal Generator AN/URM-48. (b) Frequency Meter AN/USM-26. (c) RF Millivoltmeter 411A. (d) Oscilloscope AN/USM-50A. (e) Multimeter ME-26B/U. (i) Module extender. (2) Remove module A9. (3) Turn the receiver-transmitter function switch to ON. b. VFO InPut Test. (1) Connect the AN/URM-48 between pin 1 of J2 (receptacle for A9) and chassis ground. Connect the 411A across the AN/URM-48 output.
through (7) above and adjust T2 until the indications given in (4) and (6) above are equal. Perform this step as required. (9) Replace module A9. c. Faulty Parts Isolation. (1) Insert the module extender into the A15 connector and insert A15 into the module extender. (2) Place the function switch on thereceiver-tansmitter at ON. Meas ure the voltages at the points outlined in the charts in (a) and (b) below. Compare them with the normal signal and dc voltages listed. Note: Measure all voltages to ground.
c. Faulty Parts Location. (1) Connect A16 to a 12-volt, dc-power source. Measure the voltages at the points outlined in the chart in (2) below. Compare them with the normal dc voltages listed. Note: Measure all voltages to ground. (2) Dc voltage chart.
(b) Rf Millivoltmeter 411A. (c) Oscilloscope AN/USM-50A. (d) R. F. Signal Generator AN/URM25F. (e) Frequency Meter AN/USM-26. (f) Module extender. (2) Insert the module extender into J13 (receptacle for A17). Insert A17 into the module extender. (3) Set the AN/URM-25F output signal frequency to 5.6 mc. (4) Connect the AN/URM-25F between A18J2 and chassis ground. (5) Connect the 411A between pin B of A17J1 and ground. (6) Connect the ME-26B/U between pin F of A17J1 and ground.
Figure 69. Module A17, parts location b. Gain Test. (1) Connect the AN/URM-25F between pin F of A18J1 and ground. Connect the 411A and the AN/ URM-26 across the AN/URM25F output. (2) Adjust the AN/URM-25F frequency to 5.6000 mc as indicated by the AN/USM-26 and the level to 4 millivolts, as indicated by the 411A, (3) Disconnect the 411A from the AN/ URM-25F and connect it between A18J2 and chassis ground. (4) A normal output signal voltage at A18J2 is 0.1 volt rms, as indicated by the 411A.
(a) Signal voltage chart. Point of measurement Q1 Ql Ql Q2 Q2 Volta (rms) base -------------------—--emitter ---— ---------------collector -------------------base -——-----------------emitter--— ------------------ 0.002 0 0.200 0.0025 0.0037 1.4 Q200Wctor --------------------- J2 ---------—------------—--- 0.095 (b) Dc voltage chart.
A20J2 and connect the AN/USM-26 to that point. (15) Press the push-to-talk switch. (16) The AN/USM-26 should indicate 11.5485 mc ±300 cps. (17) Release the push-to-talk switch. (18) If the indications obtained in the procedure given in (5), (6), (9), (120), and (16) above are not normal, proceed to the alignment procedures in c below. (Do not dis turb equipment settings or connections.) (19) If the indications obtained above are normal, the A19 testing is completed. c. Alignment Procedure.
Figure 71. Module A19, parts location. Place the alignment cover (fig. 28) on A20. (3) Insert themoduleextender into J16 (receptacle for A20). Insert A20 into the module extender. (4) Connect the AN/URM-43A to ANT connector J2. b. Frequency Accuracy Test. (1) Set the receiver-transmitter BAND switch at 30-52, and the function switch at ON. (2) Connect the 411A and the AN/USM26 to A20J2. (3) Press the push-to-talk switch. (4) The AN/USM-26 should indicate 11.451 mc ±500 cps, and the 411A should indicate 0.
(b) DC voltage chart. Point of measurement Q1 tW3~ ------------------Q1 emitter -------—--— ------Q1 collector ---------------—-CR1-C4 junction --------------Q2 base ----~--------—----—R8-R7 junction --------------a}lake this measurement Volts (de) 5.9 5.7 0 4.8 4.7 4.0 peakto-peak with the .W,’USW50.A. (4) After replacing a faulty part, repeat the procedures given in b, c, and d above. (5) Replace module A23. Remove the module extender. 90. Isolating Trouble in Module A21 (fig. 85 and 73) a.
(3) Adjust the output of the AN/URM48 until the voltage indicated on the 411A is 100 millivolts. Record the AN/URM-48 setting, which should be about 20 microvolt. (4) Increase the AN/URM-48 output 6 db above that noted in (3) above. (5) Increase the AN/URM-48 frequency until the voltage indicated by the 411A is 100 millivolts. (6) Connect the AN/URM-48 to the AN/ USM-26. Record the frequency indicated by the AN/USM-26. (7) Adjust the AN/URM-48 frequency to 11.
Point of mewurement Millivolta (rms) Q5 colleotoro ---------------Q5 baeeo ------------------Q6collecto@ ------------------Q6 ksec ---------------------- 160 49 1.65 volts 150 aMake this meamrement with the ANAJRM-48 output adjusted to millivolts. bMake tbie ~e~urement with tbe AN/URM-48 output adjusted tO 100 micr0v01t8. 80 cMake this measurement with the AN/URM-48 output adjusted to 5 miorovok (b) DC voltage chart.
given above for 300 cps, 2 kc, and 3 kc. Normal test results for each setting is 3.5 percent. Normal output signal level for each setting is 1.4 volts rms. (4) If the audio distortion output level is found to be greater than the prescribed levels, proceed to c below. c. Faulty Part Isolation. (1) Set the TS-382F/U to 1 kc, and adjust its output for a l-millivolt rms indication on the ME-30A/U. (2) With the push-to-talk switch pressed, measure the voltages at the points listed in the charts in a and b below.
c. Faulty Part Isolation. (1) Measure the voltages at the points listed in the charts in (a) and (b) below. Compare them with the normal signal and dc voltages listed. Note: Make all voltages to ground. (a) Signal voltage chart. Point of measurement Q1 bese -------------------- Q1 emitter ----------------Q1 collector ---------------Q2 emitter ---------------Jo ---------— ------------ Millivolts (rma) 39 35 2.0 volts 8: (b) DC voltage chart.
(8) Increase the TS-382F/U frequency to 160 cps. The ME-26B/U indication should remain zero. (9) Increase the TS-382F/U frequency to 170 cps. The ME-26B/U inication should be infinity. (10) Deere as e the TS-382F/U frequency to 140 cps. The ME-26B/U indication should be zero. (11) Decrease the TS-382F/U frequency to 130 cps. The ME -26 B/U indication should be infinity. c. Faulty Parts Isolation. (1) Set the TS-382F/U frequency to 150 cps and the level to 20 millivolts at A24J1 pins 1 and 2.
Figure 76. Module A24, parts location. (3) Measure the voltages at the points listed in the charts in (a) and (b) below. Compare them with the normal signal and dc voltages listed. (4) After replacing a faulty part, repeat the procedures given in a and b above. (5) Replace A21. Note: Make all voltages to ground. (a) Signal voltage chart.
Figure 77. Module A25, parts location. d. Remove retaining ring (12) fromshaft assembly (30) and remove shaft assembly (30), with thrust washer (31) and 0-rings (29), from housing assembly (59). e. Remove pin (5) that secures arm (4) to housing assembly (59) and remove arm (4) and spring (6). Remove bushing (3) from sleeve (2). f. Remove taper pin (7) that secures sleeve (2) to shaft assembly (16) and remove sleeve (2).
o. Remove spring (83) and sleeve (84) from mask assembly (53). p. Remove retaining ring (79) that secures arm assembly (78) to shaft assembly (57). Remove arm assembly (78). q. Remove spring (56) from arm assembly (78) . r. Remove thrust washer (70) from shaft assembly (69). Remove taper pin (68) from gear (67); then remove O-rings (65) and gear (67) from shaft assembly (69).
assembly (63) on shaft assembly (75). Align the holes; insert and secure taper pin (62) and setscrew (64). f. Place thrust washer (77) and spur gear (73) on stud (74) with the gear hub facing away from housing assembly (59). Mount gear arm (72) on stud (74) while obtaining gear mesh between gear arm (72) and shaft assembly (75). Install retaining ring (71) on stud (74) and secure. Check all parts for freedom of operation. g.
Figure 78. Selector mechanisrn, exploded view.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Retaining ring Sleeve Bushing Arm Pin Spring Taper pin Setscrew Screw Lockwasher Plate Retaining ring Taper pin stop Setscrew Shaft assembly Thrust washer Spring retainer Thrust washer Gear Worm Thrust washer 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Bushing Lamp Housing Flat washer Lockwasher Screw O-ring Shaft assembly Thrust washer Spring Arm assembly Retaining ring Retaining arm Anti backlash gear assembly Thrust washer Ba
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1 2 3 4 5 6 7 8 Coupling assembly Screw Support bearing assembly Hexagonal nut Washer Board assembly Header-shield assembly Cover 9 10 11 12 13 14 15 16 Lockwasher Panhead screw Board assembly Washer Panhead screw Support bearing assembly Screw Retaining ring Figure 79. Module A10, exploded view.
COLOR CODE MARKING FOR MILITARY STANDARD RESISTORS COMPOSITION-TYPE RESISTORS WIREWOUND-TYPE RESISTORS Equal Width Band BAND A— Signifies Composition-Type BAND A— Double Width Signifies Wire-wound Resistor COLOR CODE TABLE BAND B BAND A COLOR FIRST SIGNIFICANT FIGURE BLACK BAND D BAND C CO1OR SECOND SIGNIFICANT FIGURE COLOR o BLACK o BLACK BROWN 1 BROWN 1 BROWN RED 2 RED 2 RED ORANGE 3 ORANGE 3 ORANGE YEL1OW 4 YELLOW 4 YELLOW 10,000 SILVER GREEN 5 GREEN 5 GREEN
Figure 85.
Figure 86.
Figure 87.
APPENDIX REFERENCES TA 11-17 TA 11-100 (11-17) TM 11-1257 TM 11-5057 TM 11-5097 TM 11-5129 TM 11-5133 TM 11-5551E TM 11-5820-398-10 TM 1l-5820-398-20 TM 11-5820-398-20P TM 11-5820-398-35P TM 1l-6625-200-12 TM 1l-6625-261-12 TM 1l-6625-320-12 TM 1l-6625-400-12 Signal Field Maintenance Shops Allowances of Signal Corps Expendable Supplies for Signal Field Maintenance Shops.
INDEX Paragraph Additional equipment required: Fourth echelon testing procedures--Third echelon maintenance --------Alignment: Power amplifier tank module A2 ---Sidestep oscillator module A20-----Tuning capacitor: C1 C2---------------------------Variable frequency oscillator module A9 ----------------------------Amplifier, power, A29, theory --------Antenna: Dummy, fabrication --------------Loading network, theory ----------Audio: Amplifier, receiver, module A25, theory -------------------------And control
Paragraph Page A18--------------------------A19--------------------------A20--------------------------A21--------------------------A22--------------------------A23--------------------------A24--------------------------A25--------------------------Power amplifier circuit -----------Third echelon --------------------- 87 88 89 90 91 92 93 94 39 38 133 135 136 138 140 141 142 143 52 45 Localizing troubles, third echelon ----- 38 45 Maintenance: Fifth echelon: General ----------------------Scope -------
Paragraph Publications, index ------------------Quarter-wave network, module A19, theory - - - - - - - - - - - - - - - - - - - - - - - - - - - Reassembly, selector mechanism -----Receiver: Audio: Amplifier module A25, theory --Output power test -------------Catching range test - - - - - - - - - - - - - - Distortion test - - - - - - - - - - - - - - - - - - If.
Paragraph Page A2 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - A3 A4 A5 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - A6 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - A7 A8 - - - - - - - - - - - - - - - - - - - - - - - - - A9 A10 A11 A12 A13 - - - - - - - - - - - - - - - - - - - - - - - - - - - - A14 A15 - - - - - - - - - - - - - - - - - - - - - - - - - - - - A16 A17 A18 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 72 73 73 74 75 76 77 78 79 80 81 82 83 84
By Order of Secretary of the Army: EARLE G. WHEELER, Official: J. C. LAMBERT, General, United States Army, Chief of Staff. Major General, United States Army, The Adjutant General.
PIN: 018817-000
This fine document... Was brought to you by me: Liberated Manuals -- free army and government manuals Why do I do it? I am tired of sleazy CD-ROM sellers, who take publicly available information, slap “watermarks” and other junk on it, and sell it. Those masters of search engine manipulation make sure that their sites that sell free information, come up first in search engines. They did not create it... They did not even scan it...
