Tech: sound resets on AFM (WPC 95)

[surgeonB]

I was hoping to get some input on a recent problem...hang in there
while I give the scenario.

I installed the UFO mini saucers kit during a recent shop on a
purchased AFM.
Thereafter, after teh machine was on for a while, when I destroyed
the mother ship my sound would cut off and restart at a higher
volume. After the ball was lost this would often reset to a normal
volume.

Not linking the installation of the UFO kit to the problem I followed
Clays guide and changed the amplifier chips on the sound (AV)
board....which didn't help.

I then thought maybe I should disconnect the UFO mod from my power
supply and see if it happens...and the sound reset did NOT happen.

Since the UFO mod draws from the 5 volt circuit, I checked my voltages
on tip 101 and rather than 5 volts, I had 4.75-4.8.

By disconnecting the UFOs, my voltage stayed closer to 4.8

If I measure voltages on the CPU board...they are the same 4.8

If I disconnect the J210 the power to the CPU board, my voltages at
tip 101 are close to 5 volts.

If I disconnect all cables leading away from the CPU board but leave
J210 connected, the voltage is still 4.75-4.8 on both the CPU and
driver board.

All pins on CPU chips and connectors appear ok. No burnt connectors.
I did not reseat my ROM chip

Testing diodes on the controller board and all diodes test ok forward
however D7 and D8 (5 volt circuit diodes) are not "out of range" as
expected when multimeter leads are switched.

I have not tested any capacitors or resistors yet.

My question is : Is it my CPU board that is the problem or regulation
of my 5 volt circuit located on the controller board? Could it be the
diodes at D7 and D8. Any suggestions on next step.

Thanks

[John Wart, jr]

Your 5 volts is low most likely because the diodes and/or caps for the +5
circuit are worn out or bad. It could be the voltage regulator, input
connectors or any number of other things too.

I'd concentrate on the 4 diodes and the cap first, if that doesn't work,
then look at the regulator.

That should be 4.95 or higher to be rock solid. Any lower is asking for
problems.

"surgeonB" <bn...@aol.com> wrote in message
news:4b0d955b-efc7-441b...@k19g2000prh.googlegroups.com...

[surgeonB]

On Apr 11, 12:24�pm, "John Wart, jr" <johnwar...@johnwartjr.com>
wrote:

> > Thanks- Hide quoted text -
>
> - Show quoted text -

that is what I thought. I can't find my spare caps...I might have
given them to somebody, so I will have to order some. May take me a
week to do it now. I 'll post follow up.

It is interesting though that the machine doesn't reset, only the
sound does.

[martin]

I've seen that before. It is indeed a low 5V supply at the AV board.
Last time, it was the thermistor in the power box. But that is not
what is troubling you: the machine does it when warm.

I'm not convinced that it is the caps, either.

The LM317K is a 1.5A device, and it could be that the UFO mod has
taken it close to the edge. The good news is that you can easily up
the voltage by changing a one or two small parts. That might be in
Clay's guide. If not, we'll figure out how to get you back to 5V.

[surgeonB]

> Clay's guide. If not, we'll figure out how to get you back to 5V.- Hide quoted text -

>
> - Show quoted text -

I fixed the problem. For future reference I will post my solution.

Actually I am not sure what solved it exactly so I will explain.

On the driver board I replaced diodes d7 and D8..which didn't help

I then replaced c1 with a 570 mfd capacitor which didn't help.

I then replaced Cap C9 which didn't help.

I went to replace the voltage regulator LM317 at Q1 and found out I
didn't have the correct part. I tightened the screws to the heat sink
and was waiting for my parts to arrive. I also was scanning my board
under an improved magnifying lens I picked up and noted that one of
the legs on the C! capacitor was not soldered through the board
adquately and I added some solder to that leg. I then put the board
back in so I could play the game with a friend one evening and thought
I would demo the UFO mod lights to him. Nonetheless.....voila....NO
resets of the sound board. The next day I checked voltages on my 5
volt circuit and was getting a steady 5.2 volts.

Not sure if it was the heat sink to the voltage regulator or C1, but
no problems since. I rebuilt the power supply connector to the driver
board and CPU board anyways just in case it was a connector problem,
however I had been connecting and disconnecting the board regularly
during this process in order to try and decipher what component was
the problem.

Hope this helps someone in the future.

Thanks for everyones support and advice.