[FIXED] Bally 6803 HMM Sound issue / problem - white noise

[cNp]

Hi, I recently picked up a Bally HMM from a barn (I'm keeping a thread going in the Shop Logs section) and it has a sound issue where it very loudly plays white noise over all the actual sound effects. I've searched and found lots of advice for missing sounds but not for this problem.

Video:

You can hear the speech and the odd sound effect but not much of the music really.

I've adjusted both volume pots but they just make the white noise louder... reseated all the socketed chips and pulled and replugged the 2 connectors to no avail. Light on sound board flashes 6 times, the 5th flash is much longer than the others.

Any advice of what to check next appreciated.

 

[myPinballs]

Change DAC, Also check the op amps before the amp section

If you aren't comfortable fixing sound pcbs then you can send to me and ill fix it for you. (For a fee) These 68000 sound boards are cool, if not alittle overkill for what they did with it.

 

[James]

That's the meltdown no?

 

[cNp]

Change DAC, Also check the op amps before the amp section

If you aren't comfortable fixing sound pcbs then you can send to me and ill fix it for you. (For a fee) These 68000 sound boards are cool, if not alittle overkill for what they did with it.

Cheers, I will try replacing the DAC but may have to send to you if that doesn't work

The parts manual just says AD7533 and a part number but not sure which variant of the DAC to order... JNZ, KNZ, LNZ...

 

[cNp]

That's the meltdown no?

Yes, Heavy Metal Meltdown. Loving the theme!

 

[cNp]

Cheers, I will try replacing the DAC but may have to send to you if that doesn't work

The parts manual just says AD7533 and a part number but not sure which variant of the DAC to order... JNZ, KNZ, LNZ...

Scratch that, the chip itself has JN on it so I'll get there JNZ

 

[biglouieuk]

The longer term fix for the DAC seems to be to remove a cap off the board?! HERE

• DAC 7533 Failures on Sound Boards.
• Bally put out a service bulletin that they were having problems with the 7533 DAC (digital to analog converter) chip on many of their sound board (including the Turbo Cheap Squeak TCS and the Sounds Deluxe board, used exclusively on the 6803 series of games.) As the game is powered down and the +5 volts falls, a 47 mfd cap attached to pin 1 of the DAC goes higher than the +5 volt line. This causes the DAC chip to fail. The solution is to remove this capacitor from pin 1 of the DAC. This eliminates the transient condition on the DAC chip. Note the position of this cap is different, depending on the exact sound board used (see table below.)
  
  

  Pinball Board	Series	Board Name	Remove Cap
  A084-9	1855	TCS Turbo Cheap Squeak (Pinball)	C30
  A084-9	1864	Sounds Deluxe (Pinball)	C12

  HMM is Sound Deluxe as you know Chris.

If you take a cap out, would that need a jumper wire @myPinballs ?

Or should it be replaced by a smoothing cap that doesn't cause the power surge that causes the issue mentioned?

Just curious...

 

[Arv]

Says just remove, so I guess that's all you need to do.

 

[cNp]

Thanks very much for the advice @myPinballs ... new DAC just arrived and it's sorted the sound out, sounds great even though I haven't turned it up yet

I can now play a few games and see if there's anything less obvious that needs any attention.

 

[biglouieuk]

Now whip that capacitor out with a hot shovel...

 

[myPinballs]

Thanks very much for the advice @myPinballs ... new DAC just arrived and it's sorted the sound out, sounds great even though I haven't turned it up yet

I can now play a few games and see if there's anything less obvious that needs any attention.

You are welcome.