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(Topic ID: 218445)

Stern SB100 Sound Board Muting Problem

By WiZaRd15425

5 years ago



Topic Stats

  • 4 posts
  • 2 Pinsiders participating
  • Latest reply 5 years ago by Quench
  • No one calls this topic a favorite

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#1 5 years ago
OP
 
GMC

WiZaRd15425

Pinside member

US Connellsville, PA

9y 20,900 32 2

I have a Hot Hand which the SB 100 sound board works perfectly for 45 min to an hour then suddenly mutes the amps.
I can turn it off, wait 15 minutes and all is fine again. Then just repeats muting after and hour being on.
For some reason pin 1 on the LM380's is going low.

Does anyone have any idea what could cause this. I have recapped the board and installed a new 2n3904 at Q6 and 2 new LM380 amps.
It is a revision C1 board and its muting ciircuit is different than schematic. It does not use pin 25 from cpu reset signal.
I can't seem to find a up to date schematic for the C1 muting circuit.

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#2 5 years ago
 
PIP

Quench

Pinside member

8y 114K 8,039

Have a look at Service Bulletin #11 in the Stern Parts Catalog (1979):

http://www.pinwiki.com/wiki/index.php?title=Bally/Stern#Parts_Catalogs

The rev C-1 SB100 boards have the modification in the service bulletin, minus the extra capacitor.

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#3 5 years ago
OP
 
GMC

WiZaRd15425

Pinside member

US Connellsville, PA

9y 20,900 32 2

Thanks Quench, but I already have that revision done at factory. I have a C1 board.

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#4 5 years ago
 
PIP

Quench

Pinside member

8y 114K 8,039

OP
Quoted from WiZaRd15425:

For some reason pin 1 on the LM380's is going low.

Pin 1 on the LM380's should sit around 7 volts under normal operation from memory.

What's happening to the logic level of output pin 6 of U6 when the problem occurs?

Do your LM380's still have the copper heatsinks or has someone removed/lost them?

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