MPU is on the bench. Only get one LED flicker on power up. Removed U2 and U6 and tested in another MPU and it booted, so I'm assuming U2 and U6 are good. Board did have some corrosion which I abated, replaced several components, including U8 socket. Suggestions?
Quoted from zacaj:Jumpers the same?
That's a good one!
Are the jumpers correct?
Quoted from Inkochnito:U7 socket too?
Check the U2 socket.
Popped off the plastic upper on these two sockets and the pins looked good.
Also replaced U11 socket while I was there (found it to have a few corroded pins).
I found C12 broken while I was working on U11 (maybe I broke it). It is an axial cap, looks like a resistor. Is there some reason why this shape cap is used instead of a ceramic disc?
Quoted from Inkochnito:Are the jumpers correct?
Yes
So after replacing U11 socket, and checking the pin connections, inspecting U7 and U2, and replacing C12 (with a ceramic disc), now I don't even get a flicker. 
Quoted from JethroP:Popped off the plastic upper on these two sockets and the pins looked good.
Also replaced U11 socket while I was there (found it to have a few corroded pins).
I found C12 broken while I was working on U11 (maybe I broke it). It is an axial cap, looks like a resistor. Is there some reason why this shape cap is used instead of a ceramic disc?Yes
So after replacing U11 socket, and checking the pin connections, inspecting U7 and U2, and replacing C12 (with a ceramic disc), now I don't even get a flicker.
C12 is just a bypass cap for U11. The MPU more than likely would run fine without it. Ceramic disc vs glass capacitor was just a choice at the time of manufacturing. Bally went back and forth on capacitor style so its not really important which flavor of bypass cap is used. Probably whatever was cheaper. The axial glass caps may have some kind of manufacturing advantage too.
Double check the last thing you worked on... U11 socket change would be suspect. No bent over pin on U2 ROM etc.
Quoted from barakandl:Double check the last thing you worked on... U11 socket change would be suspect. No bent over pin on U2 ROM etc.
Yep, last thing worked on I replaced the LED. Found it in backwards. So fixed that and got 6 flashes on the bench. Installed the board in the game and got all 7 flashes but the displays didn't come on. Game went into attract mode but won't start a game. Pressed the test button in the coin door and was able to scroll through the menu, even some (not all) of the displays came on.
I had replaced the female pins on the MPU wires connectors. I'm suspecting I need to replace the header pins too. Could there be something to check before I begin that daunting task?
Quoted from JethroP:Yep, last thing worked on I replaced the LED. Found it in backwards. So fixed that and got 6 flashes on the bench. Installed the board in the game and got all 7 flashes but the displays didn't come on. Game went into attract mode but won't start a game. Pressed the test button in the coin door and was able to scroll through the menu, even some (not all) of the displays came on.
I had replaced the female pins on the MPU wires connectors. I'm suspecting I need to replace the header pins too. Could there be something to check before I begin that daunting task?
What happens in display test will give you a clue as to where to look.
Latch Strobes enable the display. So a single completely blank display that has power could be latch strobe problem.
Digit drive turns on a specific digit for every display. Same digit always on or always off on every display could be a digit drive problem
BCD Data tells the decoder chip what number to draw on the display. Displays count in the wrong order could be a BCD issue.
With a logic probe in display test you can check all the display signals leaving J1 right at the header pin post. All should pulse.
Connectors connectors connectors. usual suspect
Quoted from barakandl:Connectors connectors connectors. usual suspect
Took the board out and replaced all the header pins on the board, so all the connectors on MPU have been replaced, headers and females. Put the board back in the game and same thing. Displays are blank unless I do the self test, then they light somewhat. I put in my spare MPU and everything works fine, so I can deduce the problem is on the original MPU.
With the MPU on the bench I checked trace continuities around J1 pins 10, and 20-28. I believe I have a bad C58, as I compared readings to my good board. Also, I checked the voltages at U14, U19, and U20. Do these results suggest where the problem lies?
Screen Shot 2020-06-20 at 3.07.13 PM (resized).pngits hard for me to decode your chart without tearing into the schematic. Checking at J1 is probably easier to tell whats going on.
Do you have test ROM? During leon test every pin of J1 should cycle high and low except for display blanking should just be one little blip every cycle. If there is a problem somewhere in the logic before J1 (besides two signals shorted together) you would likely notice one J1 connector pin always high, always low, or is floating/no signal. All should pulse during display test too.
J1 P7 would not be used in 6 digit games with out a sound board, but still pulse in the test ROM.
Quoted from barakandl:its hard for me to decode your chart without tearing into the schematic. Checking at J1 is probably easier to tell whats going on.
Here's what I have done, maybe will shed some light on the problem: I took the U2 and U6 proms out of the board that is showing blank displays (although I do get 7 flashes on the LED). Put them in a known good board (jumpered for these proms), and get the same results....7 LED flashes but blank displays. To see if I have bad wiring or bad displays I installed the WEEBLY MPU and the game boots perfectly and all displays work. Hurray for the WEEBLY Universal MPU!
So, does this sound like a problem with the U2 and U6 chips? Would these cause blank displays after boot?
There's a shadow on the u6 eprom but it looks like a 2532.... you see 2532 in the chip # at the bottom?
You should get test chips if you're going to fix a lot of MPU boards, makes it a lot easier.
Quoted from slochar:There's a shadow on the u6 eprom but it looks like a 2532.... you see 2532 in the chip # at the bottom?
You should get test chips if you're going to fix a lot of MPU boards, makes it a lot easier.
I uploaded a better pic. Yes, I see 2532 as part of HN462532. I'm never sure when it comes to chip nomenclature. I never think I'm going to fix a lot of MPU boards, but I have worked on a few. Still learning. I'll check into getting test ROMs.
Fathom will boot to blank player displays if all the balls aren't detected in the outhole. Make sure the three balls are there.
Quoted from Quench:Make sure the three balls are there.
All three balls are there. Even in the test mode, the display test shows mostly blank displays.
Quoted from JethroP:the display test shows mostly blank displays.
Be a bit more specific. What are you seeing and when.
Quoted from Quench:Be a bit more specific. What are you seeing and when.
Sure. After the 7 flashes, and all the drop targets reset, etc., and all the displays are blank.
I drop a coin in and 3 credits show up. That is the only display now working....the Credit display. I press the credit button and nothing happens; still showing 3 credits.
Press the test button in the coin door and all the lamps test ok.
Press again and all displays are blank EXCEPT for display #1. It is only showing digits in the ones and tens space. It is showing 11, then 22, then 33, etc...., not 1111111, 2222222, 3333333, etc. as you would expect. There are occasional flickers of single digits in the other displays as the test cycles,
So it's booting, just has display issues. Disconnect the displays and reconnect one at a time, move displays from one position to another to see if the problems stay with the displays or move.
Double check your display voltage isn't too low, some older displays need the full +190v to turn on.
Booting up and staying up is good.....
Quoted from slochar:Disconnect the displays and reconnect one at a time, move displays from one position to another to see if the problems stay with the displays or move.
Double check your display voltage isn't too low, some older displays need the full +190v to turn on.
Booting up and staying up is good.....
Before I do that, can you tell me what difference does it make? When I install a known good MPU everything is fine. When I reinstall the original board, this is when the displays don't work. I have about 165V at TP2. The displays are only not working with the original MPU, and another MPU using the same Game ROMs taken from the original board.
The intention was to remove the displays being the issue from the equation, which I guess it already has (sorry didn't re-read the entire thread before posting).
That lets you skip a couple steps in troubleshooting because it's now narrowed down to the connector on the mpu or the circuitry from U10/U11 PIA's through to the connector. With the upper left connector removed you can probe those pins (1-7=digit enables, 10=blanking, 20-28 are the latches and BCD data) - you should get activity at a relatively good clip on all of these pins in display test.
Quoted from slochar:you should get activity at a relatively good clip on all of these pins in display test.
I do. I have pulse activity on all those pins.
Stated/restated: I have 3 MPU's I have tried in this game. One is WEEBLY Universal MPU. I put it in the game and everything works fine.
The other two MPUs are Bally 2815-35's, both jumpered identical for original factory game ROM's (U2 and U6). I only have the one set of these ROM's.
When I install either of these Bally boards in the game, swapping the U2 and U6 between the boards, I get the same results.. no displays, except for how I described in post #19.
Could both boards have the same defect? Or could the U2 or U6 be bad causing the problem(s) I am having? What more to test?
Quoted from JethroP:I have about 165V at TP2.
Is there a reason the display high voltage is only at 165V and not higher? Please bump it up a little like slochar said.
What happens in display test mode if you disconnect both the J2 and J3 connectors off the MPU board?
The start button not working might be saying there's a short in the switch matrix - some of the switch signals are shared with the display signals.. In which case you should go to switch test mode with all balls removed and all drop targets raised to trouble shoot.
If there was a problem with the U2/U6 ROMs, you wouldn't get the first LED flash on power-up.
Oh, it always helps to post clear high resolution pictures of the MPU board 
Quoted from JethroP:Could both boards have the same defect? Or could the U2 or U6 be bad causing the problem(s) I am having? What more to test?
Probably not, but the only thing is common is the 2 roms/eproms. You need a way to test those, or put other known working eproms (even if from another game) into your board under test (it won't "work" as fathom of course, but the lamp tests, display tests, should work).
Quoted from Quench:If there was a problem with the U2/U6 ROMs, you wouldn't get the first LED flash on power-up.
Unless it's only selecting U6 for some reason - I think I've had that happen ONCE, where address ranges for u2 were enabling u6 only... IIRC the software doesn't have a checksum that says "this is u1/u2" vs. u5/u6. (This could happen I suppose if you're using one of those strange jumper combos that expect a combo rom in u6 only or u2 only... was never a fan of those....)
Quoted from slochar:Unless it's only selecting U6 for some reason
Well, U6 is hard wired to test downwards to $5000 and $1000 with the top of the $1xxx range based on data in U2. But as we know the ROM test isn't completely fool proof.
I typically run a lower voltage to save some life on my displays. Anyway, I raised the voltage to 190. No change.
I disconnected J2 and J3. When I went into test mode, there were no displays at all.
I reconnected the J2 and J3, rebooted, no balls in game, all targets up, and went into test mode. The display was blank on the switch test page.
You have to have J3 plugged in to start the tests. Unplug it after the display test starts scrolling. You need to fix the displays not displaying properly before moving on to whatever's going on with the switches.
J3 is the cabinet switches including the test switch which is why you need it plugged in to start the test (alternately you can ground pin 1 of j3 with a lead momentarily to simulate a test button press if you're uncomfortable plugging/unplugging switch connectors with the power up)
Do the 2 digits that do display do so very brightly vs. when you had the working combo mpu board in there?
Plugged J3 back in. Started the test then unplugged it. So difference. No displays.
The displays that do light are the same as the combo board.
Quoted from Quench:Oh, it always helps to post clear high resolution pictures of the MPU board
Here they are....
IMG_5197 (resized).JPGIMG_5198 (resized).JPGCan you confirm the jumper between E10 and E11 is making good contact?
In game over attract mode (with all three balls in the outhole) are the playfield lamps flashing normal as expected?
With the machine OFF, if you disconnect J4 from the lamp driver board and J1 from the Aux lamp driver board, do you get normal behavior from the displays?
Note the resistor at R21 is for 6 digit display games. Once you get the displays working you'll need to change R21 to reduce display flickering on the 7 digit displays. But this is a job for later.
Quoted from Quench:Can you confirm the jumper between E10 and E11 is making good contact?
Yes, good connection. Same on both non working MPU's
Quoted from Quench:In game over attract mode (with all three balls in the outhole) are the playfield lamps flashing normal as expected?
No. Interesting....what happens end of boot, solenoids reset, game goes into attract mode, lights flashing, then the attract mode lights quit flashing after about 5 seconds. Won't start a game and no displays.
Quoted from Quench:With the machine OFF, if you disconnect J4 from the lamp driver board and J1 from the Aux lamp driver board, do you get normal behavior from the displays?
No.
Quoted from JethroP:No. Interesting....what happens end of boot, solenoids reset, game goes into attract mode, lights flashing, then the attract mode lights quit flashing after about 5 seconds. Won't start a game and no displays.
I don't suppose you can upload a video showing this (playfield activity)?
Are you swapping any other chips between the Bally MPU boards besides the ROMs?
Here is the link to the video.
No, I am only swapping the U2 and U6 ROMS, and both boards act the same.
Quoted from slochar:put other known working eproms (even if from another game) into your board under test (it won't "work" as fathom of course, but the lamp tests, display tests, should work).
Hmm, please do this ^^^ if you can, but also pull the J4 connector off the solenoid driver board so no coils abnormally activate.
It looks like it's crapping out around the time it normally would show the highest score to date.
BTW I know you said the Weebly board works, but just put that thought aside for the moment. What happens if you disconnect all displays except one and then try one other - is there any difference either time? i.e. is one display causing the problem.
Quoted from Quench:pull the J4 connector off the solenoid driver board so no coils abnormally activate.
I did this. No difference.
Quoted from Quench:disconnect all displays except one and then try one other
I did this. No difference.
Quoted from Quench:Hmm, please do this ^^^ if you can,
OK, I will take the ROM's from my Rolling Stones. Question first, do I need to change the jumpers on this board in test for the Stones ROM's to try this?
Quench: Before I remove the Rolling Stones ROM's for this test, could I install the working Stones board in my Fathom to see if the displays light? Would this tell anything? Then I can remove the ROMs and put in the board that is not working and try that.
Quoted from JethroP:OK, I will take the ROM's from my Rolling Stones. Question first, do I need to change the jumpers on this board in test for the Stones ROM's to try this?
You would - I wouldn't do this. No other games with the same rom type?
You can put the rolling stones board into the fathom to test as it is - just take off the j4 from the solenoid board like Quench suggests.
You can also put the fathom boards into your rolling stones with the same conditions, even though it's 6 digit. Pull the sound board connector when you do this it shouldn't make a difference but just to be safe.
Quoted from slochar:You can put the rolling stones board into the fathom to test as it is - just take off the j4 from the solenoid board like quench suggests.
I did this. Installed Rolling Stones working MPU in Fathom. Disconnected J4 form solenoid board as well as J1 from the sound board. No change. The displays don't come on. They flicker once during the boot, but remain off. So does this suggest the problem lies somewhere besides the MPU?
In your video above, I don't see any display glow at the bottom of the displays (could just be the video), so lets check:
On one of the displays, measure test point TP1 for +5 volts and TP2 for +190 volts.
But I must stress, use TP3 on the display as the ground connection for your multi-meters black meter lead during these two measurements..
Oh, one other thing, please confirm 100% that player 1 to 4 displays are 7 digit and the Credit/Match/BallInPlay display is 6 digit.
Quoted from Quench:please confirm 100% that player 1 to 4 displays are 7 digit and the Credit/Match/BallInPlay display is 6 digit.
I have 190V and 5V respectively on TP2 and TP1 immediately on powering up the game. Also confirm that all the displays are 7 digit except for the credit/ball in play which is 6 digit.
Hook up your logic probe. During the time between the 7th MPU LED flash and the game dying, what does your logic probe indicate at:
MPU U10 pin 39 =
Any display connector pin 10 =
Any display connector pin 4 =
Any display connector pin 5 =
Any display connector pin 6 =
Any display connector pin 7 =
Any display connector pin 8 =
Any display connector pin 9 =
Any player display connector pin 12 =
Any display connector pin 15 =
Any display connector pin 16 =
Any display connector pin 17 =
Any display connector pin 18 =
Any display connector pin 19 =
Your logic probe doesn't have the usual 3 LEDs does it?
Can you post a picture of it so we can decipher your readings?
Here's another video of something I learned. After the attract mode ends, and before trying to start a game (can't actually start a game), there are no displays. I learned that if I press any switch, target, etc., the #1 player display starts showing points and doesn't stop until somewhere around 1,250,000. If I touch another switch it takes off again....goes into the millions of points.
This is truly bizarre. Your new discovery proves communications to the displays are somewhat working.
Ok, I've been playing around a bit in emulation and I can kind of simulate what you're seeing by corrupting data in the 5101 RAM at U8.
Are you hooking up a battery to the MPU board?
Have you got any genuine 5101 RAM chips to try? Yours look like a counterfeit. The display info is held in the 5101 chip.
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Piershil
Rochester, NY