*HELP* Bally 6803 sound problems - Special Force

[DRANO]

Hi Everyone,
I'm a bit stumped on this recent game I got on the way to Allentown.
It's a Bally Special Force. Dennis Nordman's first design and a surprisingly fun pin for the money... even if the military theme is a bit severe.

Anyway, it had plenty of issues and I and another member worked on the game in the hotel (as some of you will recall ) and only just got it all working the last night before coming home.

Fast forward a few weeks, I set the game up at home and there's no sound.
I look for connection issues and find nothing.
I remove the MPU board and find a broken resistor soldered on the back of it (leading to the 6803 CPU chip). I'm told this was a common factory fix for a design flaw and I repair it... thinking it was surely the source of the problem. It did nothing... not even sure what it does? Wonder if it caused any damage?

So....

-I test the sound board using the test switch and it plays the ricochet sound effect. All good there.
-I test the connections between the MPU and the sound board. All good there too
-BTW, both boards flash the correct number of times, so I do not suspect the boards.
-Just for fun, I was instructed to swap the two PIA chips. No change.
-Running out of ideas, I pull and reseat a few more connectors... I even reverse the two pin connector going to the speaker (don't ask why) and BAMM! It starts working. This makes zero sense, but it works and I'm not going to look a gift horse in the mouth.
-I replace the back glass, press the start button, and the game goes silent again
-No amount if fiddling with connectors does anything again.

I should note that the game's plug has had the ground prong cut off. Not sure if that matters?

Anyway, I'm no electronics genius obviously.
Just wondering if any others here have 6803 experience and can recommend any other course of action.

I'm wondering if I should replace some of the 30yr old caps? Maybe a power issue?
I've also ordered new PIA chips, a 6803 CPU and a couple of CMOS chips that apparently are problematic on this system.

Just looking for any other ideas/suggestions?

Also, if anyone out there has a good 6803 MPU board and would be willing to let me try it in game, it would really help narrow things down.

Thanks.

 

[brewmanager]

It's clearly the pin gremlin that moved into my garage. Hopefully I've defeated it, but it seems like strange things are happening to machines that leave my place. Even ones like Special Force that never even got set up.

I've given up on my efforts to figure out wtf on my bk - taking it for some Santiago mclovin.

Hope Jokerz was ok....

 

[DRANO]

Well, besides the fact that the DMM is showing great connectivity between boards with everything plugged in, several sources are still suggesting that I reflow the headers and re-pin the connectors. I will report back later this weekend.

 

[g-man]

Are you getting any hiss / white noise at all ? If not, I would suspect the amp chip(s) and/or connectors before I would suspect the caps. My experience is mostly with early Bally soundboards, but failed caps usually don't result in complete silence.

I agree that it makes no immediate sense that switching the speaker wire made the sound come back. I'm thinking it was moreso the case that you may have exerted some pressure on the board in the right place at the right time and got a momentary connection that gave you the sound.

Have you, with the machine on, pressed on chips/caps/resistors to see if that temporarily restores the sounds ?

 

[DRANO]

Nope.
There's a light crackle on startup, but no "hiss" that I have noticed. I will listen more carefully next time.
I'm not really familiar with the amp chips. As you can gather, I'm a relative novice to board repair... things are just starting to make sense to me and I'm not yet fully versed on what all the chips are. Is the amp chip on the sounds deluxe board?

And yes, I have pushed and pulled and done all sorts of stuff to the various connectors and chips to see if anything happens.

Thanks!
Adriano

 

[DRANO]

Nope.
There's a light crackle on startup, but no "hiss" that I have noticed. I will listen more carefully next time.
I'm not really familiar with the amp chips. As you can gather, I'm a relative novice to board repair... things are just starting to make sense to me and I'm not yet fully versed on what all the chips are. Is the amp chip on the sounds deluxe board?

And yes, I have pushed and pulled and done all sorts of stuff to the various connectors and chips to see if anything happens.

Also, one more observation. I pressed the sound board test switch today repeatedly. On the 3rd or 4th press the test sound comes out substantially lower in volume. Not sure if this means anything?

Thanks!
Adriano

 

[Menace]

I'm still thinking where the sound deluxe PCB is doing it's self test ok (this rules out the ROMS and amp section), this is a communications issue between the MPU and sound PCB. I'm starting to think the only way to narrow this one down will be with a logic probe or scope.

D

 

[DRANO]

I'm starting to think the only way to narrow this one down will be with a logic probe or scope.

D

Damn, you just started talking Chinese :FP:

Sounds like something Mr. Spock gets during a check-up

 

[WARLOCK]

At this point, you have to watch and "view" Santiago in action. The language (although correct) means little until you can see and understand (view)
what is going on. Even then, you may be able to watch and comprehend and appreciate; but not necessarily repair on your own without assistance.

I have a couple of games with quirks that will require assistance sometime soon, and I keep plugging away on my own (without breaking or changing
anything) until you are stumped. (Trying to keep it simple as Menace always suggested takes 3 times as long to think about, with a whole lot less action)

Then you call in the pro's when you are in need. Tough, but true, then fun again.

 

[DRANO]

Well, I was partially joking.
I do know what a logic probe is. It's just that it would be about as useful in my hands as monkey using a typewriter.

Although I love to pester poor Doug for plenty of online support, I try to avoid calling in the Dr until I know the patient is critical

 

[DRANO]

Okay,
Headers have been re-flowed bewteen sound board and MPU.
Connectors have been re-built.

No change in bahaviour

I have ordered some ICs to test out that route.
I also plan to change out some line filter caps to see if I can get something happening.

Not good all around

 

[DRANO]

Got some new PIA chips in the mail today.
Looks like I'm starting with swapping out some ICs first.

 

[LiL B]

Thanks for starting this tread Drano!

I am just getting my feet wet with my first pin, I have a basic understanding of electronics and I am looking forward to the challenge of working on my own machine.

I have no sound at all even during test mode on my Bally Beat the Clock, when I turn the volume up and down I only have a low hum??

I have run a sound test using function 93 on the key board. The #65 came up on the display?

My question is, is the #65 the identifier of the issue(s) on the sound board? The only #65 I could locate on any of the manual downloads is a SW 1 P.C.B. Switch Part # E658-1

Any input is greatly appreciated

LiL B :roll:

 

[DRANO]

I'll leave that one to smarter folks than me.

Your manual should tell you how many flashes the LED on the board should give you on startup.
Each flash indicates that something has been checked and passed. If it stops short, the manual tells you where the issue likely lies.

For example. Your sounds board might requires 6 flashes to indicate proper operations.
Flash 1 might mean that the sound roms are okay
Flash 2 might indicate that the PIA chip checks out
and so on...

Have a read in your manual and watch what happens on the board at startup.
It's a good place to start hunting down the problem.

My issue is that everythign is checking out and all connections seem good... so I am a bit lost.
It's entirely possible that the circuits are broken somewhere further upstream where I cannot easily test, my filter capacitors could be bad and causing all sorts of havoc, or it could still be an issue on one of my ICs, including the CPU???

I'm basically at the point of swapping out parts until something happens. Which is not where you want to be.
If I had more skill and knew how to use a logic probe, maybe this would be easier.

Good luck!
Start a new thread and report your findings. Someone might be bale to offer help once you've ruled out a few things.

Adriano

 

[Luckydogg420]

I'll leave that one to smarter folks than me...

I'm basically at the point of swapping out parts until something happens. Which is not where you want to be.
If I had more skill and knew how to use a logic probe, maybe this would be easier.

Adriano

I've said these words before. I own a logic probe, only used it once, and not entirely sure if what I was doing was even right. I wish I could run an oscilloscope, that stuff amazes me