I’m working on a Bally -35 MPU board. When I received this board it was DOA. Solid on LED – zero voltage at U9 pin 40. I was testing it with Leon’s test ROM only. The socket for the U8 is badly corroded and needs to be replaced. I also pulled U7. I found the problem to be a bad R1 resistor. I replaced R1 and R3. Then I got a flicker and the LED goes off. I checked U9 pin 40 and get just over 6 volts. (seems high). Next I installed U1 , U2, and U6 from a Lost World game. The ROMs were working in another board. Now I still getting the flicker and the LED goes off. Seems like sometimes when I short U9 pins 39 – 40 I get one flash (hard to watch both ends of the board at once). I understand the first flash is the check sum for the ROMs – would missing the U7 and U8 cause the ROMs to not check?

Thanks

Bob

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Thanks Tuukka, I didn't think the missing RAM was my problem. I was hoping not to replace the ROM sockets but I think you're right. First I think I'll check for activity on the ROM's to see which sockets are bad.

I'm pretty sure it's jumpered correctly. It was originally in a Supersonic game. Both games had 9316A's.

Thanks

Bob

Do you think the 6 volts at U9 pin 40 is high?

Bob

Update: The weather the last few days was in the 70's F. Worked outside - cut grass, etc.

I haven't touched the board in a few days but tonight I powered it up and now I get a flicker and one flash. Don't know how you did it from Finland but thanks.

I checked the voltage and still get 6.1 at U9 pin 40 and pin 8 shows 5.23 and TP5 shows 5.25.

I checked another Bally -35 board and get 5.53 at pin 40 and 5.25 at pin 8 and 5.26 at TP5.

My power supply shows 5.32. That's the same power supply I've used for over a year and the voltage always showed 5.32. It don't seem to hurt anything.

I guess I'll install the RAM next.

Thanks

Bob

I diode tested both CR5 and CR7 = both show .58 V one way and OL the other.

I volt tested CR7 and get 6.6 on top and 5.23 on bottom - CR5 shows 6.6 top and 6.07 bottom.

By the way I replaced the U8 socket and now it boots to 6 flashes - I haven't tried for the 7th flash yet. I still get 6.05 at pin 40.

Thanks

Bob

That will be tomorrows job.

While you're here - I found an old Bally MPU I rebuilt a while back - the ROMs are marked E 838 - 19 and E 838 - 13. I looked them up and only found the -13. It said EBD? What is it for? Photo's soon.

Thanks

EBD?

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I'm curious because the board was a -35 and was re-stamped -133. The board has a resistor at R113. Is it a -35 or -133?

Thanks

Bob

I think you're right - looks better in the photo than in the flesh. I couldn't find E838-19 (U6) anywhere. If it's Eight Ball Deluxe, what should the U6 be?

I'd be more than happy to copy those ROM's and send them to you. I'd like to know what they are. What device do I copy them to?

So it IS a -35 - not a -133.

Is the R113 resistor/diode the only difference between the -35 and -133?

Thanks

Bob

I replaced CR7 (and C80 next to it while I was there). I now have 5.45 Volts at pin 40.

I spent most of the day removing headers. I must apologize for saying that Bally boards are junk. I've replaced several components, one IC socket and removed all the headers and only lost one solder pad. Maybe my technique has improved a little but I think sometimes some boards are just made better. This board has been a pleasure to work on. I've worked on some boards that if you looked at them wrong you'd lose a pad.

Thank you all.

Bob

For some reason U6 has a raised area under the sticker - almost looks lie it might be a window for erasing. U2 don't have that.

Would that indicate the solder pad was not properly prepared from the factory? I now sand and polish every solder pad before I install new parts.

I looked all through that chart and couldn't find an Eightball Deluxe U6. Now I see it's used for other games as well.

Does that mean I can reprogram those to any game I want? Are those factory EPROMs?

Thanks

Bob

I didn't think they used solder bath back then. I thought every board was hand soldered.

I use an old electric eraser. Like this: ebay.com link: Vintage Bruning Electric Eraser Tool 87 201 Engineer Drawing Drafting Works

I used it back in the days when I was a draftsman. (WOW - it must be 50 years old). It works great but the eraser crumbs are messy.

I can understand sanding on the board is destructive but so is the corrosion. Your completed boards must look really nice. What do you coat the bare traces with?

Here are some photos of the same board from the first post. Getting ready to install the headers.

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I'd like to know the answer. Some solder pads look inconsistent. But other places look like solder bath. The ground traces around the edges look like solder bath - also why would they solder the unused IC sockets (U3, U4, U5).

Those pink erasers do a nice job but too much work. And from my drafting days I'm pretty good at getting into tight places with the electric eraser. I tried those fiberglass pens and never had much luck.

Several others do that too. I've tried it a few times but end up with a mess.

Replacing the socket was the easiest socket removal I've done. Didn't lose a pad. Several of the pins broke off when I touched them but my desoldering gun cleaned them out fine. But I still don't remove them with my fingers.

The only pad I lost was on a header. Easily fixed.

I still think some boards are made better and easier to work on. This is a Bally -35. I've worked on some -17's that were really tough to fix.

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