Bubble Bobble - Sound Amp getting HOT

srarcade80

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I got a bubble bobble that had a blown sound amp. I replaced it with the same part, sound works great but man, does that sucker get hot. I can see how the original one broke. Anyone run into this issue before?
 
Yes - your amp is oscillating/fibrilating, it will work for a while but will cook itself to death. Usually this is due to missing or damaged caps between the 12V line and ground. There usually should be two, a large electrolytic, often 1200uF and a smaller polyester in the nanofarad range. These mop up any interferance on the 12V rail and stops the amp fibrilating.

Check those caps are present and not damaged.
 
The 1000uF plus cap is usually the largest on the board so easy to spot, the smaller nanofarad range one is harder to spot but it is critical, have seen amps that could fry eggs due to that being missing or smashed.
 
Taking a look at this now- i'm not spotting anything near a 1000uf cap on here. The biggest cap on the board is the only blue cap that is 330uf 25V. The rest of the caps surrounding the sound amp are 100uf, 220uf and 10uf. Then there's the various small guys too. These are all pretty common caps, I have bunches of these in my parts bins I can just replace them one at a time on the 12V line to see if that changes anything. I have the schematic to bubble bobble somewhere, I'll double check to make sure someone didn't put a wrong size cap in here at one point or something.
 
Take a look at the BB schematic but also dig out the datasheet for the amp chip itself, that will tell you the standard circuit for the chip.
 
Looking at the schematic, it looks like there is a 330mfd 25V (C36) and a 0.1mfd (C35). The parts list has it as C5 and C13 (25V Ceramic).

ken
 
Looking at the schematic, it looks like there is a 330mfd 25V (C36) and a 0.1mfd (C35). The parts list has it as C5 and C13 (25V Ceramic).

Thanks- yea that sounds like what I see. I would expect the little red guy to be the 0.1mfd. I'll replace those ones and see how it goes.
 
This may sound dumb, but check the schematic for the game vs. the cab wiring.

The schematic looks like the amp is running in bridged mode... According to the data sheet, pin 8 and pin 10 of the audio output IC are both audio outputs and NEITHER pin should be grounded. Check to see if your audio wires have one grounded. This would cause the amp to run blistering hot and burn itself out.

On the board edge connector, pin 5 is speaker + and pin E is speaker - and NOT ground.

RJ
 
The schematic looks like the amp is running in bridged mode... According to the data sheet, pin 8 and pin 10 of the audio output IC are both audio outputs and NEITHER pin should be grounded. Check to see if your audio wires have one grounded. This would cause the amp to run blistering hot and burn itself out.

Thanks, that makes lots of sense. I did convert this to JAMMA so I can move it around. I'll be sure to look at that tomorrow.

Ryan
 
I did this once when I was making a jamma adapter.


This may sound dumb, but check the schematic for the game vs. the cab wiring.

The schematic looks like the amp is running in bridged mode... According to the data sheet, pin 8 and pin 10 of the audio output IC are both audio outputs and NEITHER pin should be grounded. Check to see if your audio wires have one grounded. This would cause the amp to run blistering hot and burn itself out.

On the board edge connector, pin 5 is speaker + and pin E is speaker - and NOT ground.

RJ
 
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