Which SDB components should I check in the case where I get 4 instead of 5 volts.
(Topic ID: 170425)
Lodi, CA
Q20 is about it, there's some resistors and caps that are worth looking at but Q20 is the regulator.
Here's the schematic. Look bottom right corner of page 3. http://mirror2.ipdb.org/files/1823/Bally_1978_Playboy_Schematics.pdf
This online post says to check the C23 filter cap. https://groups.google.com/forum/#!topic/rec.games.pinball/bfieloZQ7f4
Measure the 12v unreg supply voltage. If it is also low, C23 is probably bad. If it reads 12vdc to 18vdc, than the regulator is probably bad.
Thanks all. If the problem is the regulator (q20) could I salvage one from an extra board I have? Is there any way I could test the regulator on the old board?
Quoted from DnDPins:Thanks all. If the problem is the regulator (q20) could I salvage one from an extra board I have? Is there any way I could test the regulator on the old board?
You have to test a regulator with the power on. 9-20v in and 5v comes out. There is no clear cut power off testing to do with a DMM that i know of.
Start with only the driver and rectifier board plugged in, specially after working on the voltage regulation section. Don't want to find you have a 12v to 5v short with the MPU hooked up.
Melbourne
Quoted from wiredoug:Ive seen a bad C24 do this too
Sure could if it goes short or close to it. I replace this 2.2uF electrolytic can cap with a 4.7-10uF ceramic these days
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