Re: Helluva noise when using QS6.1 with separate L & R channels!!

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Posted by Chris Tolbert on July 23, 2001 at 08:42:26:

In Reply to: Re: Helluva noise when using QS6.1 with separate L & R channels!! posted by Avelon on July 22, 2001 at 11:59:38:

My disclaimer: Try at your own risk! Don't do it if your board is under warranty!
Okay. Since your symptoms are identical to mine, you could have the same problem. When you open the case, there should be four transistors on the circuit card, very close to the outputs (closer to the aux outs if a QS6.1 is laid out the same as a QS8.1). The only four transistors side by side in a straight line on the circuit card, I think. Measure front to back resistances on them. If they are good, the resistances should be high/low from emitter to base and base to collector, and high/high emitter to collector. (I think the center pin is the base on those.) If one reads low/low between any pins, that's the culprit. Note that one guy told me these were supposed to be JFETS, in which case resistance readings would be different, but I'm just telling you what I found in my QS8.1. I removed the bad transistor with wire cutters since I wasn't replacing it. Be careful and good luck! Let us know.

: Do you mean that one of the transistors is broken?
: And I just have to figure out which one that is?
: Yes, I'm an electrician so I can measure those.
: Is it some kind of "secure" system or something?

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