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D104 TUG Amp Board Repair Experience ???

Wire Weasel

Senior Moment
Dec 13, 2008
3,192
851
223
Hey gang, I repair/refurbish D104's all the time, mostly TUG8's. A common failure is something on the amp board going bad-weak. I do collect good boards from cosmetically bad mics for parts.

I would like to repair the boards. Fairly simple. Two 2SC945 transistors and 5 caps and 5 resistors. I got a supply of the transistors in. The last weak board I ran across I began a start on a repair. This board was still working but getting weak. That the board was bad was confirmed as mic was back to normal when I ended up replacing the board with a known good one.

On the repair attempt, I removed the mounting screws, flipped it over and left it wired in. I figured it was one of the transistors going bad so I replaced them, one at a time, testing after each changeout. This yielded no results .... same weak performance. I was able to check the caps with a capacitance meter and they all seemed good. I stopped at that point, not bothering to check the resistors as I figured they wouldn't be going bad in such a low-power circuit.

So does anyone here have experience repairing these boards and WHICH component do you find is most frequently the one that fails ?

Thanks for any help !
 


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