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

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.

#2 5 years ago

PIP

Quench

Pinside member

8y 114K 8,039

Have you made any progress here?

OP
Quoted from Sonora70:
The voltages across U9 seem close EXCEPT pin 5. It should be 2.8v. Im only getting .017v ...

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?

#3 5 years ago

???

Sonora70

Pinside member

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

#4 5 years ago

???

LyonsRonnie1

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Rock Hill, SC

9y 34,550 661

OP
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

By 0 resistance, do you mean 0 as in they're not connected, or 0 as in there is no resistance (they're completely connected) ?

#5 5 years ago

???

Sonora70

Pinside member

OP
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.

#6 5 years ago

KRH

thirdedition

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

#7 5 years ago

???

LyonsRonnie1

Pinside member

Rock Hill, SC

9y 34,550 661

OP
Quoted from Sonora70:
I may have said that wrong, I'm getting no reading between pin 5 and ground. Meter stays on 0.

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!

#8 5 years ago

???

Sonora70

Pinside member

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

???

Sonora70

Pinside member

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

???

Sonora70

Pinside member

My board....

15520936443455370105401815423312 (resized).jpg

#11 5 years ago

???

Sonora70

Pinside member

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

#12 5 years ago

SPD

TheWiz

Pinside member

Chillicothe, OH

8y 45,800 272 22

ROMs are for the Six Million Dollar Man

#13 5 years ago

KRH

thirdedition

I may be crazy, but it looks like the chips in U9 and U10 are swapped.

Someone else please correct me if I'm wrong, but from what I can find that F6820P is the CPU https://www.datasheets360.com/part/detail/f6820p/-1546086776156623257/

And the two 620-29's are the PIAs

#14 5 years ago

???

jj44114

Pinside member

The f6820 is a PIA

#15 5 years ago

???

jj44114

Pinside member

The other ones are not the same. They have Bally part number. U9 is a 6800 cpu. U11 is another pia

#16 5 years ago

KRH

thirdedition

In the picture I'm seeing U9 and U11 have part 620-29.

#17 5 years ago

???

jj44114

Pinside member

The board obviously has had some corrosion and was cleaned up.

#18 5 years ago

???

jj44114

Pinside member

Yea sorry 620-29 are both pia’s

#19 5 years ago

???

jj44114

Pinside member

You need to put a 6800 cpu in U9 before you go any further

#20 5 years ago

???

jj44114

Pinside member

Sometimes when you buy used boards a shitty seller stuffs it with any chips they have on hand so it’s not empty.

#21 5 years ago

KRH

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.

#22 5 years ago

???

Sonora70

Pinside member

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.

15520983706847180298234389029598 (resized).jpg

#23 5 years ago

???

Sonora70

Pinside member

Tested the board. No change.

#24 5 years ago

KRH

thirdedition

OP
Quoted from Sonora70:
Tested the board. No change.

Try pulling U10 as well, I had a board that locked solid like that when U10 was bad.

#25 5 years ago

???

Sonora70

Pinside member

U10 pulled, still no change

15520984358785487897195702050701 (resized).jpg

#26 5 years ago

???

Sonora70

Pinside member

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

#27 5 years ago

KRH

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?

#28 5 years ago

???

jj44114

Pinside member

Remove all socketed chips except for U6 U9 and U11. See if that will give you a flicker on the led.

#29 5 years ago

???

Sonora70

Pinside member

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

???

Sonora70

Pinside member

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

#31 5 years ago

KRH

thirdedition