Ice Cold Beer sound woes

mbott1701

Active member

Donor 2024
Joined
Jul 12, 2007
Messages
927
Reaction score
53
Location
Allentown, Pennsylvania
I've been wrestling with some sound issues on my ICB. This may get a little wordy as I describe my issue and detail what I've done so far....

The game was working, then one day I turn it on and….certain sounds are faint in the speaker while others sounds normal.

Sounds that work fine:

-Heartbeat countdown
-Left motor move up/down
-Right motor move up/down
-Initial "pssht" and gurgling sound when the game is first powered up. (I guess this simulates cracking open and pouring a beer).

Sounds that are faint in the speaker:

-Target Hole
-Non-Target Hole (the oops sound)
-Bonus score counter
-Credit ("pssht" sound...the cracking open a beer sound)
-Tilt
-Music (99 bottles theme, and game over tune)


Adjusting the volume pot makes the working sounds louder, but the other sounds are still faint in the speaker.

Here is what I've done so far...

The volume pot seems to be working fine since I'm able to adjust the volume of the sounds that are working. There is also a rise and fall of static in the speaker as I turn the pot louder and softer.

I replaced the amp at U38 on the pcb.

I replaced the sound mixer at U33 on the pcb.

It seemed like I had working 8910 chips at U9 and U10 on the pcb.
According to the manual U9 should be driving some of the sounds that are faint, so I thought I'd try replacing that IC.

I got an 8910 from Bob, but when I tried to use it, it made things worse. The game wouldn't start properly and didn't function. U9 is responsible for some other function like interfacing with the watch dog timer, according to the manual. So, I put back the original chip and the game functions fine...but with the same sound problem.

And, just to be sure, I tried a different speaker, still the same issue.

I'm not sure where to go from here other than keep replacing components on the board. There is a MC68A21 chip at U28 on the pcb that seems to work with the IC's at U9 and U10. I thought I might try replacing that.

Any thoughts/advice/suggestions would be appreciated! This is one of those little annoying issues that is driving me nuts and a fresh perspective might help.

Thanks
 
Are U9 and U10 socketed? If so, swap them and see if the problem moves.

Also, looking at the schematic, C130 and 131 are 2.2uf @ 16v electrolytics that are in the filter and bias circuit for sound channel 1 (controlled by U9), whereas U10's output (sound channel 0) doesn't seem to use that. It uses 12v right from the power supply. Also, those buffer and bias voltages are controlled by the LPFON signal (haven't found where that comes from yet though)

-Ian
 
Swapping U9 and U10 didn't change anything....same sound issue.

The problem sounds are all from the U9 side, sounds channel 1, so maybe changing those caps is in order?
 
Bump. Still trying to fix this problem.

Ian,
Looks like the LPFON signal might be coming from U26? At least it seems that way when reading the Theory of Operation in the manual. I replaced the IC, just in case, but it didn't make a difference.
 
Yeah, I was looking at that. The only other thing in that circuit is are the inverters at U21 and U22. Do you have a logic probe? You could check to see if those are working. Or, you could just try changing them.

-Ian
 
Thanks. I don't have a logic probe, so I guess I just try replacing them and see if that helps. I also wonder if I should try to replace the resistors at R69, R97, and R98
 
frustrated

I checked the resitors at R69, R97, R98, and R104 and they're all fine.

I replaced the ic at U26 and the transistor at U11. Nothing, same problem with sound channel 1.

Ugh, I'm just not sure what to try next, maybe I'll just have to live with the problem. :(

The only thing I haven't done yet is change the volume pot at VR1. Is it possible that that could be causing the issue, even though it seems to work fine for increasing and decreasing the volume for sound channel 0?
 
Last edited:
I replaced the ic at U26 and the transistor at U11. Nothing, same problem with sound channel 1.

Why'd you replace U26? It seems more a problem with something after that. The sound gets played, but it's distorted - like the buffer or filter signal for that stage is screwed up. So, the LPFON signal is probably being generated, but something after that isn't doing what it should. Check those inverters.

-Ian
 
Why'd you replace U26? It seems more a problem with something after that. The sound gets played, but it's distorted - like the buffer or filter signal for that stage is screwed up. So, the LPFON signal is probably being generated, but something after that isn't doing what it should. Check those inverters.

-Ian

Thanks for the quick response, Ian. It was a shot in the dark, I guess.

Are you referring to the chips at U21 and U22?
 
Back
Top Bottom