(Topic ID: 282495)

Bally's 5V Reg Q20/TP1 meaures 10V

By mjaklrsav

1 year ago



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  • 2 posts
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  • Latest reply 1 year ago by barakandl
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#1 1 year ago

Having a boot up issue with my Bally's Eight Ball Deluxe with a solid LED.

Measure the voltages at check points and found the Rect Board voltages are to spec.
The Solenoid Driver board test points show TP1 at 10.5V which should be 5V, along with TP3 showing the same since they are tied together per the recommendation. Shorted pins 40 & 39 and nothing.

TP5 is slightly low at 10.0 rather than 11.9V.

Could it be Q20(E-710) 5 voltage regulator? or is it on of the Caps C24 or C29?
Tried pressing on the chips and reseating the connectors but did not work.
There appears to be no damage to the MPU board from battery corrosion.

Search the site for this issue but found all 5v regulators have a low voltage issue and not high voltage.

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#2 1 year ago

Low unregulated 12v is usually an indication that the filter cap is out of circuit or not doing its job. The unregulated return wire, orange in color, will often be burnt at either or both the rectifier board and SDB(A3J3P10) ends. The unreg +12v usually reads more like 15-17vdc when the solenoid driver board is connected and the filter cap is in good shape.

If SDB TP1 = 10vdc and mpu was plugged in the ram, rom, cpu, and every 74xx chip is probably toast. Voltage out = voltage in of the regulator something is very wrong and not normally a way these voltage regulators fail. Hopefully you just got your test point numberings mixed up or there is a ground potential issue from the unreg return wire being open.

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