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Need Help Identifying a Diode.

Started by TK, January 31, 2018, 11:12:23 AM

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TK

Hi guys,, just wondering if anyone can help me Identify the Diode in the picture.. It's from my BassMate 25 repair.. It turns out to be blown and is part of the Baxendal compensation system. I've tried replacing the Diode with a standard low power diode and That dropped my overheating problem to almost half the temp it was but now I'm getting crossover distortion.. Going to try different diodes In34 Germanium and a 914 just to see,, but would be nice to try and replace the original Diode,, Thank you.

tonyharker

Looks like a thermistor to me not a diode.  Diodes are usually cylindrical.  :)

TK

Hi Tony,, I'm really not sure what the heck it is,,, I thought it was a diode do to the placement,, I thought It might have been a zenor diode.. It's part of the Bax compensator,, so I'm thinking it's a Diode of some type,,, really strange looking for sure..

g1

Baxandall is a type of tone circuit.
Where is this part connected to if you follow the traces?
Is it between Q5 & Q6 where the YEV212 diode is shown?  Was it pressed up against the heatsink?
If so, I agree with tonyharker that it is a thermistor.  They may have altered the circuit from what the schematic shows.  Or it may be replacing the resistor and there still may be a diode in series with it.
If it's somewhere else, like a tone circuit, it could be a tantalum capacitor.
Measure it's resistance and see if it changes with some heat applied.


Enzo



Enzo

I would vote tantalum cap.

If it is wired to a pin on the big IC, that doubles my vote.

If you are testing this part as a diode, then it will test bad.   Test it like a cap and see.

sortedaudio

Looking at the schematic I think it's a dual diode. As the temperature of the output stage changes the voltage drop across the diode changes and alters the bias in the output stage, providing temperature compensation.  Two 1N4148 diodes in series may well do the trick. I must say the picture does look like a tantalum capacitor.

sortedaudio

TK

Thanks guys,, It turned out to be a Dual Diode,,, I think it was still good but I replaced it with 2 diodes in series.. Yes Baxandall is a tone circuit but is also a Baxandall compensation system in SS amps,, I don't know much about it at this point but hopefully will be able to find more information on it.
That thing looks just like a Tantalum Cap for sure LOL,,, The first time I tested it I did a diode test and got over 1.1 volts.. I thought,, that's strange then I did do a cap test on it and got 60 some odd pf's,, really threw me for sure.