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Replacent for vintage biasing diode on heatsink?

adeel

adeel

Active Member
Hello friends i have a nec integrated amp model is nec 10 reserve 1 .
Well i want to recape it but when i pull the driver board i found there are two biasing diodes on main heat sink .
I unscrewed them but their legs are so rusted only a movement it broke to the diode side . So i searched part number on internet but found nothing .
Can you please guide me what i can do easily ?
And are simple biasing diode which are not placed on heat sink can work here ?
And no service manual is available for nec10 mark 1.
 

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Grind away some of the plastic and solder the lead back on. Those horseshoe diodes have been out of production for decades.
 
adeel said:
And are simple biasing diode which are not placed on heat sink can work here ?
Click to expand...

If they're on the heatsink, they're for tracking changes in bias voltage of the power transistors with temperature. And if it's a triple diode, as indicated, you'll need three junction voltages.
 
So i have to use 3 diodes in series ? At least amp start to work later i can use orignal .
 
What does the schematic say? Stv3? If so it’s three diodes in series and a small pot to create the Vbe voltage spread for the output stage bias.
 
Electrically most of those are just some number of silicon diodes. An equal number of 1n4148 will sub, but the trick is the mounting. You want something thermally connected to the heat sink, not just some diodes hanging in space.

You could probably make a compact string of 3 (or however many junctions it uses) in an S shaped layout and clamp them against the heat sink with a bit of something using the original screw hole though.
 
thanks gadget73 . i decided to repair orignal one (as this is the only best option that seniors tell here) .thanks to all friends for guiding .
 
adeel said:
Hello friends i have a nec integrated amp model is nec 10 reserve 1 .
Well i want to recape it but when i pull the driver board i found there are two biasing diodes on main heat sink .
I unscrewed them but their legs are so rusted only a movement it broke to the diode side . So i searched part number on internet but found nothing .
Can you please guide me what i can do easily ?
And are simple biasing diode which are not placed on heat sink can work here ?
And no service manual is available for nec10 mark 1.
Click to expand...

See post #2 (and picture) in the thread below. Repairs are definitely possible.

https://audiokarma.org/forums/index.php?threads/kenwood-l-05m-repair-and-recap.961015/#post-14814610
 
I did that once. If tou have a dremel rotory tool, it makes quick work of it. After that I just bought a bunch of those very cheap 1N4148 diodes. They're useful in many various applications. I used them in a Sony TA-3200F To replace three of those dual diodes that go noisy.
 
Goldie99 said:
There's an older, long, thread about the 3 & 4 diode parts - https://audiokarma.org/forums/index.php?threads/replacing-the-stv-3h-and-4h-diodes.279530/

You can still order them from Germany (Ebay item # 321845661752) for a price - I have no connection to the seller, but have ordered & used some in the past.
Click to expand...
Little Diode may have some originals also. But being in the UK, shipping is high.
I did buy a couple unabtainium parts from Little Diode years ago. It did hurt a bit to pay those prices.
 
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