Haunted House
Gottlieb, 1982Sound went out and I noticed a cap on the sound board had fried c33. I believe it is a .1uf 25v. I replaced it with a .1uf 50v. Sound is now humming but I can't faintly hear the game audio in the humming. Any solutions or advice? Is the 50v too high and its causing feedback? Any help is appreciated.
Where is your heat sink that should be on the U23 amplifier (LM379S)? Your amp may be shot now since the part that holds the heat sink on is supposed to be fused to it on the top. You can see in your pic (lower left corner) where it once was.
Steve
System 80, not just a job, it's an adventure
I replaced the cap with a ceranic disc 0.1uf 50v and replaced the fuses at f1and f8 in the cabinet, both are related to sound according to the manual. Everything works fine now. The pot control is touchy but it sounds good.
Okay, cool, usually when the bracket for the heat sink snaps off, the amp eventually dies. I'd get a heat sink of some kind installed before this can happen. LM379S amps aren't easily replaced when they give out.
Steve
System 80, not just a job, it's an adventure
That was a temporary fix. The sound was distorted and when I turned it up it shut off. The cap at c33 is fine but no sound. I think I fried the little amp at u23. Found a replacement for the part lm379s at marcospecialties for $9. Even comes with the attached heat sink. Will update once I recieve and install.
The amp comes with the heat sink or the bracket that the heat sink mounts to? The pic above of the amp is just the amp and attached bracket (no heat sink). If it's just the amp and bracket you buy, you'll need the heat sink too.
Steve
System 80, not just a job, it's an adventure
Quoted from newtoit:Even comes with the attached heat sink.
on the product info for the amp it has a picture that looks like the one you attached with no heat sink. however the item description claims it comes with the attached heat sink. it references two part #'s. LM379 and XO-295.
Pin 1 is the pin leading directly to C33, correct?
Thanks for all your help. I posted this to a couple other forums and haven't received any assistance. I appreciate the time you are taking to help me sort this out.
To be sure, look up the XO-295 but it sounds like it's probably there. Yes, pin 1 connects to C33.
Quoted from newtoit:on the product info for the amp it has a picture that looks like the one you attached with no heat sink. however the item description claims it comes with the attached heat sink. it references two part #'s. LM379 and XO-295.
Pin 1 is the pin leading directly to C33, correct?
Thanks for all your help. I posted this to a couple other forums and haven't received any assistance. I appreciate the time you are taking to help me sort this out.
No problem, I usually post to RGP as well but there hasn't been much in the way of System 80 tech help asked (Actually, it's been a little slow here too. This gives me time to catch up on other projects. 
). I must have missed your post if you put one on RGP but posting here, I can use pics to help.
Steve
System 80, not just a job, it's an adventure
Quoted from newtoit:on the product info for the amp it has a picture that looks like the one you attached with no heat sink. however the item description claims it comes with the attached heat sink. it references two part #'s. LM379 and XO-295.
Wow...That's a part I thought I'd never see on a pin part supplier page.
Thanks for the info.
FYI...there is a "hack" that uses an LM1875 in place of the LM379...but it's a bit involved, and I don't yet have it on the PinWiki.
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Chris Hibler - CARGPB #31
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Put the new amp in and nothing... tried a new potentiometer as well. Both speakers read 4 ohms. Theres power to theboard. What can I do to narrow down the possibilities. Does the board have a speaker output I could measure? I'm at a loss.
We are back in action. But still no sound. I replaced a several resistors and q2, q3, and q4 all around where the batteey pack used to be. There was some clear battery acid damage but I performed surgery and brought the old girl back to life. I also did the slam switch mod. It may have been coincidental that the sound went down then the machine followed. But after working on the cpu the sound board looks like cake. Ill get back with further results on the sound.
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Bradenton, FL