Nibbler sound issue

AtHomeTech

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May 19, 2009
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I just picked up a Rockola Nibbler. Plays pretty good but after a little time some of the sounds stop playing. You still get the sound when you bump a wall but no credit up sounds and no sound when you eat a crouton. Any ideas?

-Ken
 
Bump.

Added heat sink goop to the ha1366 with no luck, still have sound for a little while after boot then half the sounds go out.

Also burnt and replaced the 2716 at IC53 (seems to be where the offending sounds come from).

Reseated all the chips and proc.

Anything else?

Does anyone repair these things? I'd do a mail order if I could.

-Ken
 
Well, spoke to soon!

It lasted several hours then it crapped out again. I think we have narrowed it down to the counter at IC48. I'll be picking one up tomorrow and putting it in.

We know the sounds are getting to thru the ROMS because the music sound hangs but it also changes when the music changes between screens. It's likely not the AMP because some of the sounds still play normally.

I'll keep the thread updated.

-Ken
 
Still no love, replaced the chip at IC43 with no change in symptops. It sometimes goes out slowly, sometimes quickly sometimes all at once and sometimes it takes a few sound cycles to die off.

Anyone taken a look at the schematic for this game and have any ideas?

-Ken
 
Pretty sure I have it fixed now. We thought for sure it was the 556 timer chip at ic43 so I replaced it. Still no love so today I got out the scope that I have NO CLUE how to properly use. I started probing inputs and outputs on the ram and roms then moved to the timer. I noticed when I hit one of the pins on the timer the music would advance. a little more digging and found the output for the time and probed it, when it had sound it was a nice wave, when the sounds died the wave was gone. Tested the 18k resister and it was good so I stole the 1 mf tantalum capacitor from c24 and whala, its working. The waveform stays constant and the game playes great!

My first real fix. Feels good.

-Ken
 
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