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(Topic ID: 210194)

Bally -35 MPU Boot/Stability (?) Issues


By spiroagnew

2 years ago



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  • 56 posts
  • 10 Pinsiders participating
  • Latest reply 1 year ago by ArcadeWhisperer
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#1 2 years ago

This is my first time messing with a Bally MPU.

I currently have a Barakandl MPU running in my Kiss--runs with no issues. Game had all .100 connectors replaced during restoration.

The game came with the original -35 board. The game booted with the -35 board in it, with original ROMs. I didn't use this board extensively, I just confirmed that it booted, I replaced it with the barakandl board during the restore.

Original battery holder removed from the -35. Coin style battery installed, with diode.

I completed the jumpers to make the board run with two 2735 eproms at U2 and U6. I burned new ROMs using my new ROM burner, ROMs checked good by the reader. These are the ROMs from IPDB, with no patches applied. When removing U6, I noticed the legs of the original chip were black.

Upon putting the -35 into the Kiss game, I got my seven flashes. The game booted and I played a handful of games with no issues. I walked away and came back and started a game, and the machine was now displaying bizarre behavior--odd sounds, garbage numerals in the score display--but the game still played. I turned the game off and rebooted, and got no flashes, not even the startup flicker. Turning on and off would get the game to boot one time out of ten, but the game would lock up randomly.

I reseated U10/U11, the 5101 and the Roms at U2/U6. The game booted, but would show "000000" in all displays for the high score, as well as other bizarre behavior. I couldn't get the thing to lock up though.

So I'm wondering if this is a ROM issue, 5101/battery issue, a socket issue, a jumper issue, or another issue I've not considered. I have extra chips from other boards that I can swap in, and sockets to install, but I don't have extra sockets for the 2735s...they're on their way from GPE currently.

Any direction would be appreciated.

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#2 2 years ago

I would never expect an original board to be reliable with original sockets.

Bare minimum, first change U2 and U6 sockets. Next add 6810. If not already done due to battery leakage, the 5101. Last, of course, is mpu and pias, bare minimum, the bottom one if any previous leakage.

Of course, an amateur can destroy a board unsoldering that many sockets.

#3 2 years ago

I'm pretty adept at replacing sockets. I thank the Hakko 808 for that. I guess I'll start with the U2 and U6 sockets when they arrive from GPE.

#4 2 years ago

Some observations...

When "cold", the game will boot. After about ten minutes, it locks up and then won't boot again until I wait a bit an let it "cool".

Chips at U7 and U9 are hot to the touch.

#5 2 years ago

Good observations. You can use freeze spray (or air in a can upside down) to re-cool chips individually to find the suspect.

#6 2 years ago

Check voltage at U7 (pin 1 negative, 24 posititive) if its high lift and check diodes cr5, cr7 and resistor r11

Edit, mixed up U7 with U8, disregard the diode check but I'd like to know what the voltages at the chips are.

#7 2 years ago

Asmig Will provide those voltages ASAP.

Another observation: the game now seems to lock up only when it flips to attract mode. When I do get it to boot, I'll play a four player game and run the machine through its paces. The game will only lock up only after the end-game tune plays...not during gameplay. Other times, I'll flip it on, get my seven flashes, and it'll lock up at the first sign of attract mode. Again, it seems to boot OK "cold", just not when "warmed up".

#8 2 years ago

Try reseating the EPROMs a few more times, it might clean the contacts. It almost sounds like it's related to where in the program it is.

#9 2 years ago

The CPU at U9 may get a bit warm, but the 6810 ram at u7 does not typically heat up much in operation. That might be a clue to try a new one.

#10 2 years ago
Quoted from barakandl:

The CPU at U9 may get a bit warm, but the 6810 ram at u7 does not typically heat up much in operation. That might be a clue to try a new one.

Swapped in a spare U7 I had on another board. No change.

I socketed the 5101 RAM because I had the socket on hand, and the one on the board was original. No sign of corrosion under the old socket. But still no change. I even tried a known good RAM. No change.

The sockets for the U2, U6 and U7 will be here Thursday according to tracking.

#11 2 years ago

I looked in my parts stash and found sockets for the U2 and U6 eproms and U7. Replaced one at a time. Still no change. Game still freezes in attract mode. When it freezes, I've noticed the green LED will quickly flash solid light during lock up. U7 still warm to the touch upon lockup.

So far here's what I've tried:

Double checked jumpers I made to make the board 2732 compatible. (Jumpers made with small gauge wire, not solid core wire, issue with that?)
New 5101 RAM, new socket for 5101
New sockets at U2 and U6.
New socket at U7, replaced chip at U7 with known working chip.
Swapped around U10 and U11. Then swapped in new chips in these locations as well.
Swapped out 6800 chip at U9.

My next steps?

New sockets at U9, U10, U11.
Another attempt at burning EPROMs?

#12 2 years ago

Did you try putting your ROMS into Andrew's board? Or take his and put them in yours?

#13 2 years ago
Quoted from eh97ac:

Did you try putting your ROMS into Andrew's board? Or take his and put them in yours?

Andrew's board that was in the Kiss is currently configured with a single 2764 EPROM at U2. I'd have to switch the jumpers around on his board to make it happen, I think.

And I figure troubleshooting one bad board is better than potentially messing up the other one and trying to troubleshoot two! Good idea though.

#14 2 years ago

I see he has update the board since I got mine. You should still be able to try your ROMS in his board after you remove the 2764 and switch the jumper.

#15 2 years ago

I've began to replace the sockets on the 40 pin chips, I've done U9 and U10 so far, no change.

I can't get past the fact that the memory chip at U7 gets so warm. When it's cool, it's fine, when it's hot, that's when I get a reset and then won't boot again 'til its "cooled off". I've replaced the chip with two others from parts boards, and both get just as warm as the original and display the same behavior. Is there a weak link somewhere in and around U7?

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#16 2 years ago

All sockets now replaced. No change.

All chips swapped out for known good chips. Some places, like U7 and U9, multiple chips. No change.

Q5 and R11 replaced. Don't know if this would make a difference. It didn't. No change.

U9 and U15 warm-ish, U7 and U14 still hot. I've got 5.2VDC on each of these at their logic high pins. One of the pins on U9, pin 2 or 6 can't remember, read 5.5VDC if that makes a difference.

Tempted to just put in the working repro board and call it a day, but I'd like to see this through. Any direction would be appreciated.

#17 2 years ago

Re-flow the solder on the J4 pins. On the wiring side board picture the solder job on the headers do not look good.

#18 2 years ago

Question. Have you looked at the driver board? Has the 5V section been tested?

#19 2 years ago

5.5vdc is awfully high and would probably explain the extra heat. Even 5.2 is excessive for an old Bally with a fixed linear regulator (Lm323K).

What do you measure for 5vdc at the SDB?

#20 2 years ago

If the 5V on the driver board is not stable nor will the logic on the MPU. If it drops below 5V the game will reset. If it is above 5V it will cause the chips to overheat. The 5V is derived from the 12v from the rectifier. If the regulator circuit is working correctly you should have a smooth 5V.

#21 2 years ago

cactusjack JT-pinball Thank you for the replies, guys. Here's what I've found...

Rectifier board is a barakandl repro. It gives a reading of 14.7VDC at the test point on the rectifier board.

The recommended mods have been done to the SDB which is original. TP1 and TP3 give a reading of 5.26VDC...the same voltage I get on the chip legs above.

#22 2 years ago

I will test voltages at the transformer tomorrow when I have more time, but here's a thing I noticed:

The rectifier in the game now was sent with a 10w600ohm resistor at R1. All my other Bally/Stern games in my collection have a 10w680ohm resistor in that spot. Looks like R1 is in line with the 12v line that ultimately supplies the 5v. I should probably swap in the 680ohm resistor and see if that makes a difference, right?

#23 2 years ago
Quoted from spiroagnew:

I should probably swap in the 680ohm resistor and see if that makes a difference, right?

R1 is specified as a 600 ohm resistor (check the schematics). They are however harder to find so your boards that have 680 ohm resistors have had it changed (commonly accepted replacement).
This R1 resistor however is on the solenoid 43V power rail - nothing to do with the 12V & 5V lines.

#24 2 years ago

At this point I think your transformer and rectifier are probably good. The lm323 5V regulator in the SDB has a tollarance of 1%. This means the voltage on TP1 and 3 if tied together should be no greater that 5.05V. Has any other work been done to the driver board?

#25 2 years ago

I have another working Bally set up beside my Kiss.

It's running at 5.24VDC at the rectifier/SDB and 5.16VDC at the Alltek repro MPU. My Kiss is missing that same voltage drop, but otherwise the voltages are the same.

The SDB has new .100 male headers, the ground/5V mods and new caps at C23 and C26. The connectors were also repinned.

I can swap out the SDB between the working Bally and the Kiss to see if that makes a difference...? Or advise if there is something else you suspect may be out of whack.

#26 2 years ago

Put the SDB from the working game in the questionable game and see if the heat up problem goes away.

FYI, there is a power path through the 82 ohm resistor and the 11.9VDC that can add power to the 5v buss. But it normally doesn't effect things.

#27 2 years ago
Quoted from CactusJack:

Put the SDB from the working game in the questionable game and see if the heat up problem goes away.
FYI, there is a power path through the 82 ohm resistor and the 11.9VDC that can add power to the 5v buss. But it normally doesn't effect things.

Alternately, I can burn Six Million Dollar Man EPROMs and try the Kiss MPU in the 6MDM. But I'll try swapping the SDBs first...as it's the easier route.

#28 2 years ago

Just to keep in mind my replacement MPU does not use 12v for anything. The stock MPU uses 12v to make the reset, diag led, and powers u8 ram.

#29 2 years ago
Quoted from JT-Pinball:

At this point I think your transformer and rectifier are probably good. The lm323 5V regulator in the SDB has a tollarance of 1%. This means the voltage on TP1 and 3 if tied together should be no greater that 5.05V. Has any other work been done to the driver board?

not when Bally wires up the LM323K like they did. They are usually putting out around 5.25vdc in that setup.

#30 2 years ago

Thanks for the discussion to help me follow through on this. So...

Repro MPU: Doesn't use 12v. Works in the game.

Original MPU: Uses 12v for RAM (among other things). Constant resets. U7 RAM is getting hot, while operating at 5.24VDC.

So my next plan of attack be to look at the 12v/5v line from SDB to MPU?

#31 2 years ago
Quoted from spiroagnew:

Thanks for the discussion to help me follow through on this. So...
Repro MPU: Doesn't use 12v. Works in the game.
Original MPU: Uses 12v for RAM (among other things). Constant resets. U7 RAM is getting hot, while operating at 5.24VDC.
So my next plan of attack be to look at the 12v/5v line from SDB to MPU?

sounds good. you could have a flaky 12v connector causing the reset to drop out or the the ram to undervolt and mess lock up the system. my replacement MPU seemingly would use quite a bit a less current than the original too making a marginal connector less likely to cause a problem.

when it is hot and locked up I'd check some signals. See if the clock stops pulsing in time (P3 and P37). See if the vua-q2 stops pulsing. Since u7 heats up check the unique chip select, (i think it is /a9?). Check the 12v test point and the reset. If the zero cross input to the pia stop pulsing could indicate a problem with u14. I think you said u14 heats up too, really shoundt unless the 82 ohm 2w resistor is baking it from below.

Make sure you didnt tear out the ground pins at J4 when redoing the headers. The ground return comes in on the topside of the pcb only (bad original design). You see a lot of people run a jumper wire from J4 ground pins to the outside of pcb ground area.

#32 2 years ago

I swapped in a known working Solenoid Driver Board. The MPU still locks up.

I did the MPU ground mod from J4 bottom pins to the ground trace.

12v test point on MPU is still at 14.1VDC.

Using barakandl 's above comment, and Clay's guide, here are some findings with my logic probe (took it out of the package for the first time).

Reset signal: When locked up, pin 2 and pin 40 of U9 are still HIGH.

Clock: Pins 3, 36, 37 of U9 are PULSE.

VMA signal: during attract mode, the U9 pin 5 is PULSE. When locked up, HIGH.

I've used Clay's guide to follow this VMA signal. Everything seems to pulse as it should during attract and HIGH when locked EXCEPT...

The guide says that when tracing the VMA signal the PULSEing of U9 pin 5 and U19 pin 8's waveform should match. When in attract mode, U9 pin 5 gives a clear pulse, BUT U19 pin 8 gives a scuzzy, sickly beep and the pulse light barely lights. Is this suspect or am I interpreting the logic probe results wrong?

#33 2 years ago

Dbl post.

#34 2 years ago

Once it is "locked up", you should expect Everything to be either high or low except for the clock signals. It indicates it is crashing the program. Which could be any number of things.

The only guidance I can give at this point is to see if you can cause and fix the heat up problem with freeze spray and solder pencil (touch tip to top center if ICs to heat up internally) or with a heat gun.

If it's not an actual IC (it sounds like you have replaced them all), then the solder pencil won't help since it could be a bad socket or trace.

#35 2 years ago

Also see this current thread with a similar problem that seems to be caused by a suspect U14 - barakandl also mentioned U14 above.

https://pinside.com/pinball/forum/topic/bally-mr-mrs-pacman

The OP in that thread used an icecube in a watertight plastic bag to freeze components and track down the issue (incase you don't have freeze spray).

#36 2 years ago

I've socketed U14, indicated by the other thread, and U19, which gave me wonky readings above. Replaced with chips from a donor board. Did them one at a time. No change. U7 is still blazing hot.

I'm about to give up. I'll try one or two more things before throwing in the towel.

#37 2 years ago
Quoted from spiroagnew:

I've socketed U14, indicated by the other thread, and U19, which gave me wonky readings above. Replaced with chips from a donor board. Did them one at a time. No change. U7 is still blazing hot.
I'm about to give up. I'll try one or two more things before throwing in the towel.

Can you take voltage readings on every pin on U7 in reference to ground? Still don't understand why so hot if not higher than normal voltage coming in.

Have you tried the Ice Cube in a Ziplock bag on U7 to see if it is the only overheated part that is causing the lock ups?

#38 2 years ago

Will try ice cube method later this evening.

U15 and U16 are still warm...but not as hot as the CPU and U7 (the latter takes the cake as far as heat).

Here are my findings for voltages in both attract and locked up states.

20180227_131156 (resized).jpg

#39 2 years ago

Okay...more information.

I used the freeze method as suggested above by CactusJack . Booted the game and kept U7 "frozen" the entire time. Had the game running for 45+ minutes and played about 15 games on it. That's the longest the game has ever been active with this board in it.

So I'm assuming it's U7, the socket, or something that drives U7 that makes it get hot.

I've had three different chips in U7. All got hot. U7 GOT hot even with the original socket.

Open to ideas, obviously!

#40 2 years ago

If there’s no shorts in the chip itself, it would get hot if something on its outputs that it is trying to drive has a short or low resistance. Check what’s on each of its outputs... resistors, caps, diodes, line traces or solder pads that may have solder joints slightly touching each other, and the ic’s that they are driving, harness wires that may have worn insulation and touching other wires or ground screws or metal frame....maybe with power off check the resistance from each output signal to ground, look for any that may be a different resistance than others (especially significantly lower).

#41 2 years ago

using the u7 chip leg's vcc and ground connection check resistance to ground and 5v spots on the board looking for excessive resistance. milliohm dmm is nice here.

#42 2 years ago

deleted...

#43 2 years ago
Quoted from srcdube:

If there’s no shorts in the chip itself, it would get hot if something on its outputs that it is trying to drive has a short or low resistance. Check what’s on each of its outputs... resistors, caps, diodes, line traces or solder pads that may have solder joints slightly touching each other, and the ic’s that they are driving, harness wires that may have worn insulation and touching other wires or ground screws or metal frame....maybe with power off check the resistance from each output signal to ground, look for any that may be a different resistance than others (especially significantly lower).

Looking at the schematic on this... ignore comment above about regarding harness wires, since this is in the middle of the board. As RAM there are no output signals that this chip alone drives... everything is shared busses. So what would make this chip drive more current than it should, but it still works OK for some time?
Address bits 17-23 are all inputs only, so not likely a problem.
R/W line pin 16... not likely the problem. If it was stuck, other chips wouldn't work.
Data bits pins 2-9... if any of the other devices on the databus are not tristating correctly, or there are some resistive paths to ground it could draw more current from the RAM. With power off check the resistances to ground on those pins. However I expect if there was a bus problem like that, then more chips on that bus would have problems, not just the RAM?
Chip Select Pins 10-15... if something is wrong with those signals, particularly stuff that decodes only to that RAM, then the RAM may be incorrectly trying to drive the data bus when other chips are driving the data bus at the same time. U18 pin 15?

#44 2 years ago
Quoted from srcdube:

Looking at the schematic on this... ignore comment above about regarding harness wires, since this is in the middle of the board. As RAM there are no output signals that this chip alone drives... everything is shared busses. So what would make this chip drive more current than it should, but it still works OK for some time?
Address bits 17-23 are all inputs only, so not likely a problem.
R/W line pin 16... not likely the problem. If it was stuck, other chips wouldn't work.
Data bits pins 2-9... if any of the other devices on the databus are not tristating correctly, or there are some resistive paths to ground it could draw more current from the RAM. With power off check the resistances to ground on those pins. However I expect if there was a bus problem like that, then more chips on that bus would have problems, not just the RAM?
Chip Select Pins 10-15... if something is wrong with those signals, particularly stuff that decodes only to that RAM, then the RAM may be incorrectly trying to drive the data bus when other chips are driving the data bus at the same time. U18 pin 15?

would think /a9 problem would show up elsewhere, but maybe not since how the other CS for the 6810 are wired. compare the /a9 pulse (inversion of) A9 or if you have another working MPU if you have one handy compare to that. *note my replacement board does not use /a9 so it can support access larger ram/rom space, so can't compare exactly to it*

check compare vua+clock phase 2 as well to a working board too

#45 2 years ago
Quoted from barakandl:

using the u7 chip leg's vcc and ground connection check resistance to ground and 5v spots on the board looking for excessive resistance. milliohm dmm is nice here.

I tried to look at this last night. I measured the resistance of the ground/5V from U7 to the other ground/5V points on all the other chips. The only non-Zero readings I got were to U9. But I tested the same points for resistance on another Bally MPU and got the same readings. So I'm not sure this is the issue. Are there other specific non-chip components in line with U7 I should be testing?

I had the game playing for quite some time last evening, about half hour, with no freezing. U7 still got warm, but it didn't lock up. However, when I turned it off and then on again, the LED stayed lit and needed to cool off before it could get its seven flashes again.

#46 2 years ago
Quoted from spiroagnew:

I tried to look at this last night. I measured the resistance of the ground/5V from U7 to the other ground/5V points on all the other chips. The only non-Zero readings I got were to U9. But I tested the same points for resistance on another Bally MPU and got the same readings. So I'm not sure this is the issue. Are there other specific non-chip components in line with U7 I should be testing?
I had the game playing for quite some time last evening, about half hour, with no freezing. U7 still got warm, but it didn't lock up. However, when I turned it off and then on again, the LED stayed lit and needed to cool off before it could get its seven flashes again.

Swap u15, u17 and u19 for sanity sake and since your handy at desoldering. That should cover the rest of the gates that triggers u7. U15 goes out the most often as it is driven really hard. Can use 7437.

#47 2 years ago

I swapped and socketed U15. Fired the game up and it ran for 90 minutes of play and attract mode with no lockup. U7 hot and U9 warm like normal but no lockup.

I called it quits and shut the game off. Turned back on and got the solid LED. So the issue hasn't gone away. May have just got a lucky stretch?

U19 replaced and socketed previously, so I'll do U17 tomorrow and report back.

#48 2 years ago
Quoted from spiroagnew:

Turned back on and got the solid LED.

When you get a solid lit LED on a warm power-up, what happens if you then do a manual reset of the MPU board - i.e. very briefly short the reset line at the CPU (U9) to ground? i.e. just quickly short pin 40 to pin 39 on the CPU.

#49 2 years ago

I socketed and replaced U17 this morning. I played the game quite a bit, and left it in attract mode for three hours or so with no resets.

U7 still hot, U9 still warm, but no resets. The off-and-back-on-again gives a solid LED with no boot.

Quoted from Quench:

When you get a solid lit LED on a warm power-up, what happens if you then do a manual reset of the MPU board - i.e. very briefly short the reset line at the CPU (U9) to ground? i.e. just quickly short pin 40 to pin 39 on the CPU.

When 39 and 40 are shorted, I get seven flashes and boot...and the game seems stable.

So quench and others: there's a problem in the reset section or 5V section, correct? I see Clay's guide has a section on this about putting a capacitor on the solder side of the board to "stabilize", but I'll let the experts chime in. Note that I have not rebuilt the reset section on this board as of yet. Does the locked on LED give any clues as to why U7 is getting hot?

#50 2 years ago

Yes sounds like you have a problem in the reset circuit. You can add the capacitor as per Clays guide but that's only masking a problem.

What's the voltage across zener diode VR1 (in the reset section) on the MPU board?
Have you run this board on the bench to see if U7 still gets hot? When you say hot, can or can't you leave your finger on it?

Your picture shows a Fairchild brand 6810 at U7 - are the other 6810 you've used also Fairchilds? I've just put a Stern MPU-100 board on the bench with a Fairchild 6810. After 10 minutes the chip gets warm (in free air). It's certainly not too hot to touch, but it's not cool either.
.

Quoted from spiroagnew:

Does the locked on LED give any clues as to why U7 is getting hot?

Not really. BTW, what happens if you put this board into one of your other Bally machines?

Can you also amuse me and remove the coin battery. Does the board still fail with a locked LED when warm?

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