(Topic ID: 354224)

Odd Bally 35 mpu behavior

By slghokie

3 months ago


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  • 25 posts
  • 6 Pinsiders participating
  • Latest reply 3 months ago by Quench
  • Topic is favorited by 1 Pinsider

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#1 3 months ago

Finally got this 35 board to boot on the bench with a pc power supply giving 5v and 12v. Boots every time. Put it in my future spa project and sometimes it boots, sometimes not. Repinned connectors from solenoid to mpu. Added a ground wire just in case it was the issue. I read some forums that talked about write speed on u2 and u6 so the ones in there are at zero speed on a GQ burner. Monitored the power and no fluctuations. Anyone see this before or know what might cause it? Did a video below…

#2 3 months ago

You only need J4 connected to the MPU for it to boot.

You may need to repin J4?

Have you checked fuse holders on the rectifier board, that they are securely holding the fuses?

Have you checked what the voltage readings are at the test points on the rectifier board?

#3 3 months ago

Rikoshay I repinned J3 on solenoid and J4 on MPU before the video. Rectifier board 5v and 12v come in steady (7.7V and 14.4V). Voltages at the MPU and solenoid test points are also solid (no fluctuations). Will look at the fuse holders. Maybe just replace the fuses for good measure.

Again, on the bench with a PC power supply doing 5V and 12V it boots every single time. Only acts odd when booting in the game.

Will likely try another solenoid board if I have a good one just to narrow down the issue.

#4 3 months ago

When bench testing, did you simulate the 43 volts to get the seventh flash?

#5 3 months ago
Quoted from slghokie:

I read some forums that talked about write speed on u2 and u6 so the ones in there are at zero speed on a GQ burner.

It's most likely not this. If you rewrote them a couple of times they are fine.

Quoted from slghokie:

Anyone see this before or know what might cause it?

Yes, this happens when the reset section transistors are reacting to the voltage that's still in the system via the large +5v cap on the SDB. If you let it bleed off voltage does it always start up? I have had boards that did this and the fix was to replace the reset section transistors. IIRC the last one in the chain Q5 is the culprit, but I replaced them all anyway.

#6 3 months ago
Quoted from Billc479:

When bench testing, did you simulate the 43 volts to get the seventh flash?

Billc479 I did not on the bench but I do get the 7th flash in the game....just intermittently as it does not always boot

#7 3 months ago
Quoted from slochar:

It's most likely not this. If you rewrote them a couple of times they are fine.

Yes, this happens when the reset section transistors are reacting to the voltage that's still in the system via the large +5v cap on the SDB. If you let it bleed off voltage does it always start up? I have had boards that did this and the fix was to replace the reset section transistors. IIRC the last one in the chain Q5 is the culprit, but I replaced them all anyway.

slochar gotcha! Will replace the trani's tonight. In other tests (not the video) I would let the voltage drop down to zero then try startup and it was hit or miss on boot. From cold (sitting overnight or for 1 hr) it seems to boot more times than not so I wondered about heat. Easy enough to replace transistors.

#8 3 months ago

slochar I replaced both transistors Q1 and Q5, and still intermittent boot in game.

#9 3 months ago

I replaced the 5v and 12v fuses on the rectifier and pushed the clips in for tighter connection. So far it seems to be more reliably booting so will mark it closed unless it comes back.

1 week later
#10 3 months ago

Well, it came back. Was booting fine in game with 2716 jumpers/roms. Pulled mpu, jumpered for 2732, future spa roms. Cleared and burned them 3 times on normal speed. Boots fine on the bench. Put in game no boot, led locked on sometimes, flash and nothing others. All the power is consistent. 12v is high like 14v on mpu. It booted once in game but is random like what it does like the video. Boots everytime I pull it and put on the bench power. Oddest thing I have seen. Anyone have any ideas? Was gonna change br2 and see if that does anything. Br2 tests file, strong ground. But “feels” like a 12v issue. Tried with minimal connectors and all connectors, again it worked before this.

#11 3 months ago
Quoted from slghokie:

Put in game no boot

What happens when you manually reset the MPU board by very briefly shorting pins 39 and 40 at the U9 CPU ?

Quoted from slghokie:

12v is high like 14v on mpu.

Not quite.
12V at the rectifier board is the voltage spec when the rail is unfiltered, i.e. the solenoid driver board is not connected. Connecting the solenoid driver board adds the C23 11,000uF filter capacitor to the rail which stores energy and brings up the voltage by a factor of about 1.4
The schematics are misleading in this respect.
Your 14V is actually a little low but not alarmingly.
Disconnect J3 from the rectifier board and measure test point TP3 on the rectifier board. If it's 9V or less (should be close to 12V), BR2 may be suspect.

#12 3 months ago

Quench UPDATED when I short cpu 39 and 40 and the led blinks when I short pins. Red reset button on mpu also does not seem to work.

Removed J3 from rectifier and test point was 13.6v so seems BR2 is ok. Also c23 on sdb is 15k not 11k

#13 3 months ago

The button on the mpu is only to reset adjustments and audits to zero nothing with resetting the CPU itself.

#14 3 months ago
Quoted from Quench:

What happens when you manually reset the MPU board by very briefly shorting pins 39 and 40 at the U9 CPU ?

Not quite.
12V at the rectifier board is the voltage spec when the rail is unfiltered, i.e. the solenoid driver board is not connected. Connecting the solenoid driver board adds the C23 11,00uF filter capacitor to the rail which stores energy and brings up the voltage by a factor of about 1.4
The schematics are misleading in this respect.
Your 14V is actually a little low but not alarmingly.
Disconnect J3 from the rectifier board and measure test point TP3 on the rectifier board. If it's 9V or less (should be close to 12V), BR2 may be suspect.

What adds to the confusion is they list the high voltage as 230vdc which is what is with the filter cap in circuit... opposite of the 11.9vdc(come on bally, just call it 12v).

#15 3 months ago

Pics in case it is helpful

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#16 3 months ago
Quoted from barakandl:

What adds to the confusion is they list the high voltage as 230vdc which is what is with the filter cap in circuit... opposite of the 11.9vdc(come on bally, just call it 12v).

That one wasn't in my memory bank - thanks for the reminder

Quoted from slghokie:

Removed J3 from rectifier and test point was 13.6v so seems BR2 is ok.

Rectifier board J3 = SDB J5 = MPU J2 ---> i.e. the 12V power rail.
If you're getting 13.6V with J3 disconnected at the rectifier board, and 14V with it connected you have a problem with the connections leading to the C23 filter capacitor on the SDB.
With rectifier board J3 connected, measure the voltage directly on the legs of that capacitor. If you're getting zero volts diagnose where you're losing connection to it (more likely the ground line either at SDB J3-10 or rectifier board J3-17).

Quoted from slghokie:

Also c23 on sdb is 15k not 11k

Someone's installed a new capacitor, they came with 11,000uF from factory. 15,000uF replacement is fine.

#17 3 months ago

Well, I checked from regulator board pin 17 to SDB pin 10 and have connection. Have connection to MPU. Worked on the pins for 12V that go to the 15k cap and they had continuity between the pins with arrows in the pic. I cleaned and desolder/resoldered where they did not have connection between the 2 pins with arrows but still same result, no boot in game but boots on bench. No other major parts in the line unless the disc cap I highlight in the picture matters. Pulled the SDB connections, and remeasured the regulator board with main power and J3 off. I get 13.7 on TP3. If I reconnect it all I get 14 at TP3, then 13.9 at SDB test point 5 is 13.9 and MPU TP2 is 13.9. When I have reg board and SDB hooked up the 15k cap has 14v on + and no reading on neg.

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#18 3 months ago

Unless your meter's faulty or doesn't handle no-loads properly the readings don't make sense.

Please report the voltage measured directly on the C23 capacitor legs.

#19 3 months ago

Sorry, I misunderstood. First readings were each leg individually. 2 different meters across the cap legs gives 14.1

#20 3 months ago
Quoted from slghokie:

2 different meters across the cap legs gives 14.1

Hmm, filtered vs unfiltered voltages aren't making sense. Only way to resolve this would be to look at it with an oscilloscope.
Anyway, measure the voltage ripple at any of the 12V test points. To do this set the meter to AC voltage this time. With a good 15,000uF capacitor at C23 you should get in the vicinity of 0.3VAC

Quoted from slghokie:

Cleared and burned them 3 times on normal speed.

BTW you mentioned the board worked with 2716 EPROMs but stopped booting reliably in game once you converted to 2732 EPROMs.
The default programming algorithm for these old EPROMs on the GQ-4X burner is insufficient and doesn't program the cells deep enough. You need to set the program speed to slowest '-2' and enable double write. Program them 3 or so times in a row (without erasing in between). A program cycle as spec for a 2732 device should take nearly 3.5 minutes!

#21 3 months ago

Maybe the C(r)apXon cap is just bad. They where part of the capacitor plague in the early 2000s. It could be from that era.

#22 3 months ago

Success!!!!!!! Thank you Quench the roms was the issue!

Thanks to barakandl and slochar as well.

#23 3 months ago

Just a thought... I wonder if the diode on the sound board in series with the 12v is shorted and that is why the 12v stayed up around 14v with the SDB's C23 cap out of circuit.

#24 3 months ago
Quoted from barakandl:

Just a thought... I wonder if the diode on the sound board in series with the 12v is shorted and that is why the 12v stayed up around 14v with the SDB's C23 cap out of circuit.

barakandl The sound board is currently plugged in and works...although the sound is faint. I turned up the knob on the sound board but it is still faint. I had not done anything to the sound board yet and plan to do the caps, that pot, and can check that diode. Easy enough to replace at the same time just to rule it out.

#25 3 months ago
Quoted from barakandl:

I wonder if the diode on the sound board in series with the 12v is shorted and that is why the 12v stayed up around 14v with the SDB's C23 cap out of circuit.

Wouldn't have been that. The unfiltered 12V measurements were done with J3 disconnected from the rectifier board so nothing downstream was connected. Bit of a mystery..

Quoted from slghokie:

I turned up the knob on the sound board but it is still faint. I had not done anything to the sound board yet and plan to do the caps

Could be the capacitors and/or the old input bias design issue with the LM741 at U9.

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