(Topic ID: 116454)

Bally MPU Locked On LED - been testing and stuck


By parkway

4 years ago



Topic Stats

  • 38 posts
  • 11 Pinsiders participating
  • Latest reply 3 years ago by balzofsteel
  • Topic is favorited by 3 Pinsiders

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#1 4 years ago

So was bored this weekend and decided to rebuild a solenoid driver board (SDB) I had lying around along with a spare MPU board with working Fathom roms (I tested it in my Fathom and it worked). MPU rebuild went great and tested good with a known, good working SDB. On to rebuild the spare SDB now. So, long story short, in my haste and while distracted on the phone with my brother, I installed the 5v regulator in backwards. Didn't realize this until I turned her on and *pop*, blew R50 on the SDB. Had my nicely rebuilt MPU in there too. Awesome. Stupid mistake.

So this is where I'm at with the MPU using a known good SDB (will have to figure out what I damaged on the rebuilt one later): LED locked on. Getting 5v at the two test points on the MPU. Pin 40 on U9 goes high as it should. Shorting pin 39/40 on U9 (or jumping r1/r3 junction to TP4) as suggested in the guides does NOT cause the LED to flicker or start flashing (LED still locked on). I also checked the voltages on the legs of a couple of other chips suggested in the guide and they seemed a little high (like 3.3 instead of the 2.5 like it should be). I swapped out what I am pretty sure are good U9 and U11's and LED still locked on.

Could I have fried something in the reset? I'm guessing with the voltage regulator in backwards I dumped some current into the MPU and blew at least a couple things up. Any suggestions? Again, I'm not horribly worried since these are spare boards, but it would be nice to have a spare set to fall back on just in case (without dropping $300+ on Alltek boards). Not to mention, a good learning experience (like don't install the regulator backwards a__hole!). Thanks.

#2 4 years ago

I should add that the MPU before I rebuilt it had zero acid damage (and was working fine after the rebuild anyway).

#3 4 years ago

No one? I've followed Clay's guide and have repaired these before, but something isn't adding up and just looking for a "fresh set of eyes".

#4 4 years ago

Getting a good 5VDC is what should trigger at least a start of the boot sequence. So it comes on solid and just stays that way? Not even a quick wink? I've rebuilt a couple that were acid damaged and the only time I had a solid lock-on like that was when I put one of the game roms in the wrong place.

#5 4 years ago

Not even a quick wink. And MPU is getting a nice, solid 5v at both test points that should be 5.

#6 4 years ago

You may have sent the whole 12V or so down to the 5V ICs.
every one of them needs to be checked.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#7 4 years ago

Ok. Dumb question, but how do I check them? Anything a DMM can do?

#8 4 years ago

The 5101, 6810, 6821, and 6800 can all be tested in another working board.
The other discrete logic ICs might be able to be tested via...

http://www.pinwiki.com/wiki/index.php?title=General#Testing_an_integrated_circuit

The test isn't 100% conclusive, but you should be able to compare the test results against the same tests on a known good board.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#9 4 years ago

Great. Thanks very much. I just so happen to have some spares of all of those, so I guess I'll swap them in and see. Is there anything else I might have particularly blown up besides IC's?

#10 4 years ago

You can remove all the socketed chips except U6, U9, and U11 and still get the flicker. Once you get it working that far you can start adding the other chips.

#11 4 years ago

I would quickly check Q2 and the Led.
You s/b getting a pulse from U11 pin 39 to toggle the transistor.
If not ..... I would go back to U9 and start there.
* I assume you are bench testing this board!

#12 4 years ago

Yes it's on the bench; good boards are in the machine itself. I'll give pulling the ic's a try and go from there as long as this blizzard doesn't knock my power out.

Is Q2 the same scr as on the lamp driver board? Looks very similar.

#13 4 years ago
Quoted from parkway:

Yes it's on the bench; good boards are in the machine itself. I'll give pulling the ic's a try and go from there as long as this blizzard doesn't knock my power out.
Is Q2 the same scr as on the lamp driver board? Looks very similar.

no

it is a transistor. go to great plains electronics. search for a the bally mpu rebuild kit. download pdf with part layout.

#14 4 years ago

Some Bally/Stern MPUs will not boot on the bench when using a PC power supply. Give it a try in the game.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

#15 4 years ago
Quoted from barakandl:

no

it is a transistor. go to great plains electronics. search for a the bally mpu rebuild kit. download pdf with part layout.

Ok, thanks.

Quoted from ChrisHibler:

Some Bally/Stern MPUs will not boot on the bench when using a PC power supply. Give it a try in the game.

Good to know. I will try it in game.

#16 4 years ago
Quoted from ChrisHibler:

Some Bally/Stern MPUs will not boot on the bench when using a PC power supply. Give it a try in the game.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

I have 3 on my computer desk now. They will Boot.
I would hate to try to T/S this MPU in the machine.
Just my thoughts....

#17 4 years ago
Quoted from barakandl:

no
it is a transistor. go to great plains electronics. search for a the bally mpu rebuild kit. download pdf with part layout.

Q2 is an NPN transistor..... 2N3904
You can test it with an analog or digital multimeter.
You s/b able to buy it locally with the Led, if you have a local electronics store nearby.

#18 4 years ago
Quoted from JKnPA:

I have 3 on my computer desk now. They will Boot.
I would hate to try to T/S this MPU in the machine.
Just my thoughts....

It depends on the reset timing and how fast your power supply stabilizes. If the reset, derived from the 12v line, goes high before the 5v is solid, it locks up or flickers once. You can try triggering a manual reset by shorting p40 and p39 together on u9 cpu.

#19 4 years ago
Quoted from JKnPA:

I have 3 on my computer desk now. They will Boot.
I would hate to try to T/S this MPU in the machine.

I don't know what T/S is, but computer switching power supplies respond to the load. I've had several MPUs that refused to boot from the computer PS, but when connected to the real PS, boot perfectly fine 100% of the time. You must have been lucky thus far. I pulled my hair out over one of these the first time it occurred.

What does T/S mean?
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#20 4 years ago

T/S = troubleshoot, I'm guessing

I've given up on the Bally/Stern reset circuitry. I've just had too many of them that failed to reset reliably on the bench and, more importantly, in the game. I now use Dallas reset ICs on my boards and have had great success.

Chris knows my frustration first-hand as he went to power up my Quicksilver at Expo last year and it took a few tries before it finally reset. Now with a Dallas IC it resets every time.

#21 4 years ago
Quoted from ChrisHibler:

I don't know what T/S is, but computer switching power supplies respond to the load. I've had several MPUs that refused to boot from the computer PS, but when connected to the real PS, boot perfectly fine 100% of the time. You must have been lucky thus far. I pulled my hair out over one of these the first time it occurred.
What does T/S mean?
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

T/S....... trouble shoot.
My main point was to try to work on it outside of the machine for
easy access and part replacement.
I mentioned Q2 first because it is very inexpensive and easy to replace.

#22 4 years ago

I'm going to dig into this more after work tonight. I actually do have some 2N3904's lying around (no idea why) so I'll replace that while I'm at it.

Clay has something about the Dallas on his guide and I found it interesting. I skimmed it before but maybe I'll give it a thorough read and try it out one day.

Yeah it is nice to bench test things instead of swap them in and out of the machine, but I heave heard others say that sometimes it doesn't work.

#23 4 years ago

I bought these as I either couldn't find stock or a good price on the part in Clay's write up (not realizing that GPE carries an alternative.)

ebay.com link

Ed's part is here:
https://www.greatplainselectronics.com/proddetail.asp?prod=MCP130-460DI%2FTO

The main difference between the two is the pinout and the reset delay. Either will work and you end up removing a bunch of components from the circuit. I think you really only have to remove about a half dozen components to isolate the "new" reset circuit from the "old" circuit, but there will be many more unused components you can remove if you want.

#24 4 years ago

Awesome, thanks. I like Ed so I will most likely grab it from him when I'm ready. I have another MPU that I have to fix (and this time hopefully not blow up), so maybe I'll go that route with it.

#25 4 years ago
Quoted from parkway:

I'm going to dig into this more after work tonight. I actually do have some 2N3904's lying around (no idea why) so I'll replace that while I'm at it.
Clay has something about the Dallas on his guide and I found it interesting. I skimmed it before but maybe I'll give it a thorough read and try it out one day.
Yeah it is nice to bench test things instead of swap them in and out of the machine, but I heave heard others say that sometimes it doesn't work.

1. Don't replace the transistor unless it is bad.
@ I'm not saying it is bad; just an easy check.
2. Bench testing...... you test your know Good MPU. If it tests Ok, then you can compare it to your
Bad MPU.
* Just my opinion/just trying to Help!

#26 4 years ago

If pin 40 of the CPU is high than the reset section is probably working.

I think using the Dallas reset generator is not worth it unless you are already replacing all components in that area due to corrosion.

#27 4 years ago
Quoted from barakandl:

If pin 40 of the CPU is high than the reset section is probably working.
I think using the Dallas reset generator is not worth it unless you are already replacing all components in that area due to corrosion.

The Fathom board I've been talking about, pin 40 does go high so I'm not too worried about the reset. I think you guys are correct about one or more IC's being bad. I'm not going to go tinker with anything that doesn't need it.

The other spare board I have (out of a Centaur that was in a flood) has some acid damage and I bought it for a few bucks to basically just screw around with and work on for fun. That one I know has a shot reset section so I was thinking of trying the Dallas route on that.

#28 4 years ago
Quoted from JKnPA:

1. Don't replace the transistor unless it is bad.
@ I'm not saying it is bad; just an easy check.
2. Bench testing...... you test your know Good MPU. If it tests Ok, then you can compare it to your
Bad MPU.
* Just my opinion/just trying to Help!

I hear ya'. I appreciate it.

#29 4 years ago
Quoted from barakandl:

I think using the Dallas reset generator is not worth it unless you are already replacing all components in that area due to corrosion.

Agreed. I only put it into the Wiki for completeness. The only time I've actually used the reset generator was for that particular board. I like the part mapping that's in the wiki. It makes picking the right parts during the repair easy.

Quoted from JKnPA:

My main point was to try to work on it outside of the machine for
easy access and part replacement.

I certainly agree that it's much easier to work on the board out of the game. It just doesn't work sometimes.
--
Chris Hibler -CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#30 4 years ago

Ok. I had some time to monkey around with this. I decided to rule out the chips so I took a known working (as in tested it tonight) board and swapped U9, 10, and 11 from the "bad" board into the working board. Using those chips from the bad board, the good board gave me a flicker and began to boot, so I know that those are good. So that narrows it down to the ROMs I guess. My reset circuit seemed to test ok, so maybe I isolated it to the ROMs themselves? Glad I at least didn't blow up U9 thru 11.

#31 4 years ago

Make sure the rom jumpers are set correctly.

10 months later
#32 3 years ago

I have I be doing exactly the same thing...... For a 6 million dollar man pin ....... Brand new 6800,6820 jumped for 2716s freshly burnt and checked numerous times as well as swapped cpu and pia....... Re-verified all traces numerous times ..... Still locked on ..... I'm suspecting Roms as well ..... Any good known source for these Roms ??? The files I got came from ipdb suppose to be converted for 2716s but I'm second guessing that at this point

#33 3 years ago

First thing I check is reset circuit by shorting CPU pins 39 and 40 together. If that doesn't work then I move on to ROMs and such.

#34 3 years ago

I had the same issue the OP had recently. (Even caused by a junk sdb that I was testing)

I had similar voltages 3.3v instead of 2.4v. Ended up I had no clock signal due to a bad U15.

From doing my reading it seems it's a somewhat common failure component.

#35 3 years ago
Quoted from Slim64:

I had the same issue the OP had recently. (Even caused by a junk sdb that I was testing)
I had similar voltages 3.3v instead of 2.4v. Ended up I had no clock signal due to a bad U15.
From doing my reading it seems it's a somewhat common failure component.

U15 shits the bed so often....

Put your DMM on P3 and P37 of u9. One should read 2.4vdc the other 2.6. If you have a scope or frequency counter. Check the clock speed right at those points. Needs to be about 0.6MHz.

U15 is pushed to the absolute max at 5vdc. Then the power supply on these bally games can run at up to 5.4vdc.... U15 fails.

7437 is rated a bit better than the original device at u15. Use those.

#37 3 years ago

Clock? U16?
Shotgun... replace all untested chips... esp logic chips since they are usually $<1

#38 3 years ago

Had a really stubborn -17 board a while back. Still not booting after some logic chips. All that was left near the roms was a few .01uf bypass caps and it was one of those. Surprise! Bally put cheap caps on the MPU just like on the p/f switches.

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