(Topic ID: 210194)

Bally -35 MPU Boot/Stability (?) Issues

By spiroagnew

3 years ago


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  • 56 posts
  • 10 Pinsiders participating
  • Latest reply 2 years ago by ArcadeWhisperer
  • Topic is favorited by 3 Pinsiders

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There are 56 posts in this topic. You are on page 2 of 2.
#51 3 years ago
Quoted from Quench:

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

Coin battery was one of the first things to go. There's a NVram with a new socket in there now.

Quoted from Quench:

BTW, what happens if you put this board into one of your other Bally machines?

I had it in the 6MDM early on. Same lockup behavior as when in the KISS. This was long before the apparent stability I've currently stumbled upon.

Quoted from Quench:

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.

I can place my finger on it for a few seconds before it becomes uncomfortable. I've only used Fairchilds at U7 thus far.

#52 3 years ago
Quoted from spiroagnew:

There's a NVram with a new socket in there now.

This might confuse matters, but have you done barakandl's recommended changes to the reset circuit after installing the NVRAM which from memory is to remove R11 (the 82 ohm 1W resistor that gets hot) and replace diodes CR5 and CR7 with a jumper links?

#53 3 years ago
Quoted from Quench:

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.
.

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?

if i recall I remember reading clay's guide says to use 470uF or something to extend the reset delay. That cap is about 10x too large of value. I played around with it once and I think I got a 1uF ceramic cap to greatly extend the reset delay. I don't think this is your fix and I would bodge in a MCP-130-460 reset device before doing the cap trick. You can put the MCP-130-460 across the legs at u9 on the back of the board and then can cut out most of the reset crap in the bottom left corner. The reset chip connects just the +5v, gnd and reset.

#54 3 years ago

Ah sorry, I went off ancient memory of Clays guide. Just looked and the addition of the 470uF is more a suggestion to test delaying the reset. But yeah, 1uF is more like a reasonable value.

The voltage across the 8.2V zener diode in that circuit controls the short reset hold time on power-up based on the slightly longer time for the 12V line to reach supply rating.
If the voltage across this zener is less than 7.8V then I'd change it. If it's close/just under 7.8V then for test, you can try temporarily adding an extra diode in series with it which will add another 0.6V to the release threshold of the reset.
Also test resistors R112, R1, R3 and R2 to make sure they're in spec.

2 weeks later
#55 3 years ago

I've returned to button this one up for now, if anyone is following along.

The game has stopped locking up, and it has seen quite a bit of use. The shotgun replacement of U15, U17 and U19 as suggested by barakandl must have done the trick.

As for getting the game to boot back up when it's already been running, I went lazy route and installed a MCP130-475...and it works like a charm. I can now turn the game off and back on and get the game to fully boot. The first flash is a bit longer now due to the MCP130 holding the signal for longer than the reset section would, but the MPU does the job reliably now. For any novices, here's the component I used...

https://www.digikey.com/product-detail/en/microchip-technology/MCP130-475DI-TO/MCP130-475DI-TO-ND/275234

...and I followed Clay's guide to install (Leg 1 (Reset) to Q5's leg closest to R11, Leg 2 to +5VDC and Leg 3 to Ground).

I've learned a lot in this thread, and I wish to thank everyone that chimed in. You guys are great. In solving this, it's boosted my confidence--so much so, last night I grabbed another non-working Bally MPU with some mild corrosion and boot issues I had laying around, and this evening it's currently fully working in my Harlem Globetrotters! Another one saved! Thanks again!

11 months later
#56 2 years ago

I know I am late...but wanted to throw something in here for others that may be looking for a reset problem.

If the game powers on with a solid LED and doesn't reset...but you can force a reset and the game will work fine...your rectifier board in the bottom of the cabinet may be bad. Without getting into a ton of detail...one of the power resistors on the rectifier board may have opened, and will give you all kinds of issues with the reset circuit on power up.

There are 56 posts in this topic. You are on page 2 of 2.

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