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View Full Version : Repair Log: Stern SB-100 soundboard



AskJacob
10th August 2008, 12:31 PM
Symptoms:

Screeching on powerup. No other sounds.

Repair:

Found that C53 missing from the board (!). Replacing that and C51 (same value) reduced the screech to a single startup sound.

Tidied up many many dry and cracked looking solder joints

New Symptom:

Now plays single sound (beeeooow!) then hums on switch on. Hum remains until MPU finishes booting, then silence. No sounds work still.

Repair:

A bit of digging around the circuit diagram, and see if there is something around the reset circuit that can explain what is going on. Q6 (3904) controls the reset on the PCB, and measured pretty weird - low where it should be high, and high where it should be low. Replaced that, and kept checking around the reset circuit. C42 which is a 10uf Electro measured like a resistor, so it was replaced.

New Symptom:

All sounds available, but way out of tune. Background hum still there. Tuned the sounds to my bad ear (had my working board to compare to but still fiddly!). Replaced the remaining 2 electros on the PCB C47 and C55 as so far all the others have been out - no suprise considering their age!

Seems all good to me now!

These boards are needlessly complex for the basic sound they make!

Cheers
Jacob