Hi Jared
All or some of these transistors are approaching obsolete but should be
obtainable by post from the internet.
I would suggest getting a bag of them (they are not expensive) then you
can match them using a multimeter for similar Hfe.
(note, don't hold them for long as the finger temperature affects gain!).
You could simply fit one and it will work but distortion would be
reduced by matching. I don't suppose Neotek matched them originally though.
It may be worth running the multimeter over the whole circuit comparing
it to others (DC conditions) as there may be something else amiss.
Matt S
Jared wrote:
Hello everyone
I'm having a problem with a series 1 mic pre (just the mic pre, line in is fine). I'm getting a lot of noise and extremely distorted signal. Everything looks fine visually. I swapped the chip and that didn't fix it. My next thought was that it could be caused by a bad transistor on the front end of the circuit. So I did a little looking and now I'm a bit confused.
It seems that I need either of these transistors: 2SAB737, 2SA991, or 2SA1084
I'm sure their are others but this is what is in my console and the 2SA1084 was
written in some of the documentation that I have. Does anyone have a lead on
where these can be sourced or other replacement options? Also what is the best
way to match them? Can it be a simple DMM hFE test?
Also maybe I'm going down the wrong path, any other thoughts about what could
be causing this?
Sorry for the long post,
Thanks,
Jared
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