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2270 Bias Diode Replacement

Allegroconbrio

Allegroconbrio

Working the problem
I'm in the process of recapping a Marantz 2270 receiver and was less than careful working on the power amp boards - I broke the lead off the H761 bias diode. I've read other posts suggesting 1N4002 as a replacement, but Mouser and Digikey only has the axial style, rather than the existing box-shaped diode.

My concern is that an axial diode will have a smaller contact area with the heatsink, and may overheat. Is there a way to address this, or better yet, does anyone know of a box-shaped replacement? I'm I being OCD about this?

Thanks!

Rich W
 
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Bias diodes usually measure temperature, so it won't overheat regardless. It isn't dissipating much of anything. If the other channel measured one diode drop with your DVM set to "diode check", than just about any conventional diode will work. You might also be able to use the base-emitter junction of a small transistor if the package were more suitable. If it's a diode setting a current bias on a current source it still shouldn't be dissipating much and most anything will work. If it has more than one diode drop (contains more than 1 diode) you need to duplicate that. Hopefully the people who know that unit specifically will chime in.
 
Thanks Conrad,

I've sourced a corresponding diode (which is also attached to the power transistor heat sink) from a 2240 donor unit. It seem to be a slightly different model, but if it has identical voltage drop as the existing broken bias diode, I'm going to try it.

Any Marantz experts, please chime in if you think this solution will result in smoked outputs.

Rich
 
It all depends on the forward voltage of the diode. I'd be measuring the diode for the other channel to get an idea of a starting point for a replacement.
 
H761 is a SM-150-01 which I believe has a forward voltage of 0.8 to 1.0 volts depending on which source you believe.

I think a 1N4007 would be a good choice for replacement.
 
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