(Topic ID: 237706)

Bally -35 board not flickering.....still trying to learn boards

By Sonora70

5 years ago


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#1 5 years ago

I have a "clean" -35 board I'm trying to get to boot to use in another pin. The light locks on with no flicker. I've been following Clays guide. Some results I'm getting at U9 include:
pin 40 is going to 5.3 v
pin 2 is going to 4.8 v
When I short R1 and R3 to ground pin 40 goes low.

The voltages across U9 seem close EXCEPT pin 5. It should be 2.8v. Im only getting .017v, almost no voltage at all. Obviously getting that same voltage at TP7. Could this be my problem? Any ideas on what could be causing this? Thanks.

#3 5 years ago
Quoted from Quench:

Have you made any progress here?

This might be a symptom of a locked CPU rather than cause of the problem. In any case measure the resistance between that pin 5 and ground (I get around 4.6M ohms with the black lead on the ground plane of my board). If you get a substantially lower resistance it could be shorted at input pin 8 of U19.
What voltages are you measuring on pins 3 and 37 of the CPU?

I'm getting 0 resistance between pin 5 and ground.
When I measure voltage at pins 3 and 37 I'm getting 2.7-2.8v

#5 5 years ago
Quoted from Sonora70:

I'm getting 0 resistance between pin 5 and ground.
When I measure voltage at pins 3 and 37 I'm getting 2.7-2.8v

I may have said that wrong, I'm getting no reading between pin 5 and ground. Meter stays on 0.

#8 5 years ago
Quoted from thirdedition:

What kind of eproms are you using, and are your jumpers set correctly?

It has 9316 aprons. I have no idea about the jumpers? How would I know?

#9 5 years ago
Quoted from LyonsRonnie1:

Yeah it's a tricky thing, different meters work different ways, on my meter 0 would mean they're completely connected (no resistance between them) but on your meter, 0 means they're not connected (infinite resistance between them) the exact opposite!

My meter is acting as if the leads are touching nothing. I tried a continuity test and there is no continuity.

#10 5 years ago

My board....

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#11 5 years ago

I have no idea what the board came out of.....

#22 5 years ago
Quoted from thirdedition:

So I was only a little crazy. I believe the 620-28 is the Bally 6800 CPU.
If you don't have a 6800 CPU you aren't going anywhere.

Had a 6800 in another old board and placed it in U9.

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#23 5 years ago

Tested the board. No change.

#25 5 years ago

U10 pulled, still no change

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#26 5 years ago

This is a picture of the bottom left reset section just for viewing

#29 5 years ago
Quoted from thirdedition:

That is a bummer, not that I have any expertise, but unfortunately what limited knowledge I do have is running out. Your board is jumpered correctly for the roms and you now have as far as I can tell the correct chips in the right place.
Do you know the roms you have in the board are good? To get a board to start to boot I believe you only need U6 in. Are you sure those are working roms?

I'll look to see if I have more rooms off another board.

#30 5 years ago

Took all the chips out of another board.....no luck. Should I rebuild the reset section? It looks clean.

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