Service manual

Using the schematic in Fig.(s) 43 or 44, check the output of the three
regulators.
Note: For control board #2402 type only, if the scoreboard used a
battery, a dead battery could cause U1 to shut down. If you suspect
this, remove the battery connector from the control board and
resume testing the scoreboard on AC power only.
Determine the type of control board you have by referring to Figs. 29 and
30 on pages 5-1 and 5-2 of this manual.
The 115 VAC power is reduced to 24V center tapped by T1 and rectified by
D5 and D6. The resulting 15 volt unregulated DC is supplied to the voltage
regulators U17, U18, U19 to generate regulated 14V, 8V and 5V. See Fig.
44 below.
Figure 44 #2860 Control Board
The AC input from the transformer is rectified by D1 and D2. The
resulting 15V unregulated DC is supplied to the voltage regulators U8,
U16 and U2 to generate regulated +5V, +7V, and digit pwr.
The data cable consists of two pairs for wires with a shield wrapped
around each pair. The “data” uses one pair and the audio uses the other
pair. If shielded wire is not used, the “data” will cause “noise” to be heard
through the speaker.
If you suspect that the data cable may be bad, check your data cable using
the following methods:
Unscrew the phone plug and inspect the wires.
Using an OHM meter, measure the resistance of the cable, see Fig. 46 on
the following page.
Step 3
Electrical Power
#2860 Control Board
Electrical Power
#4290 Control Board
Data Cable
Step 1
Step 2
7-10
Trouble Shooting-Data Cable