Owner`s manual

transformer is defective. If the other channel reads incorrectly as well, follow the

instructions in the next section (2b) below.

2. If your Stereo 70 has NO SOUND FROM EITHER CHANNEL and the

filaments are illuminated – follow the steps in this section

a. Apply power to your Stereo 70. Check to see if the filament is illuminated in

the GZ-34 rectifier tube.

• If it is illuminated proceed to the next step (b) below.

• If it is not illuminated replace the rectifier tube.

• If the replacement rectifier tube filament still does not illuminate use your

Digital Voltmeter (Set to AC Volts

at the 20 Volt Range) to measure the voltage

across

pins 2 & 8 of the GZ-34 rectifier tube. Remember, this is an AC voltage

measurement. The correct reading is 5 Volts AC.

• If this voltage is zero, the power transformer is defective and must be

replaced.

b. Apply power to your Stereo 70. Using your digital Voltmeter measure the

voltages at each of the four sections of the Quad Electrolytic Capacitor. The

following Voltages are typical:

• Section “A” (Designated by a Square): 305 VDC

• Section “B” (Designated by a Triangle): 375 VDC

• Section “C” (There is No Designator): 415 VDC

• Section “D” (Designated by a Semi Circle): 435 VDC

The last two readings can vary depending upon the bias setting of your amplifier.

Any value above 400 VDC for sections “C” & “D”, will be OK in this case.

• If you obtain the correct measurements (all) remove the power and measure

the 15.6 Ohm Bias Resistors as described in the previous section 1e.

• If all of the measurements are near zero volts or below 100 VDC

, replace the

rectifier tube.

• If replacing the rectifier tube does not restore the correct readings, check the

AC Voltage at pins 6 & 4 of the rectifier tube

(relative to the chassis) – the

correct reading is 330 VAC. Remember this is an AC Voltage reading and you

must set your voltmeter accordingly. If you fail to obtain this voltage reading,

the power transformer is defective and must be replaced.

• If all of the readings are low (between 100 VDC and 200 VDC

) replace both

the rectifier and the Quad Electrolytic Capacitor.

C. HUM (with RCA Input Shorting Plugs Installed)