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Old 21st May 2004, 11:07 PM   #1
Wagener is offline Wagener  South Africa
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Default thermal runaway diodes

Can I use 1n4007 instead of the 1n4004 diodes?

this is used for thermal runaway protection in the leach amplifier.

the diodes are mounted in the heatsink
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Old 21st May 2004, 11:46 PM   #2
maylar is offline maylar  United States
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Yes, although it's somewhat of a waste. The 1N4007's are high voltage.
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Old 21st May 2004, 11:56 PM   #3
markp is offline markp  United States
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The difference in cost is about $0.02 between the two. As long as you are over 3 times the voltage in the circuit you are safe.
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Old 22nd May 2004, 12:44 AM   #4
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I think the threadstarter asked if 1N4007 has the same function as 1N4004, he might happen to have just these...

For heat sensing the diode is forward biased and don't need a high voltage resistance in normal case if it's not going to experience backwards bias voltage of higher value.

to the issue, I can't for sure answer on your question BUT a higher voltage diode USE TO HAVE larger forward voltage drop, you should of that reason try to find 1N4004, or else trim in your tempsensing with 1N4007, in other case it might happen it wont protect because the 1N4007 won't decrease enough at high temperature so the circuit will eventually not protect from overheating!

Disclaimer: In the case of Leach amp, I don't now how it look like there so my answer is in general.

Cheers
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Old 22nd May 2004, 12:48 AM   #5
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ultima, is there also smoke in tubes?
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Old 22nd May 2004, 12:52 AM   #6
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Ich glaube so, aber nicht sicher, und do?
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Old 22nd May 2004, 12:58 AM   #7
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when i destroyed them the smoke did not come out
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Old 22nd May 2004, 01:00 AM   #8
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Quote:
Originally posted by Ultima Thule
Ich glaube so, aber nicht sicher, und do?

Here in Sweden we say "no smoke without fire", so I guess
transistors glow too if there is smoke inside them, but we
cannot see it.


As for the leach amp, I think it is an accurate description that
it has a Vbe multiplier, with four diodes and a resistor (actually
two for some reason) from C to B and a trimpot from B to E.
The diodes are mounted on the heatsink, not the transistor.
I think, but am not 100% sure, that it wouldn't matter which
diodes are used as long as the trimpot is adjusted correctly.
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Old 22nd May 2004, 01:01 AM   #9
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Quote:
Originally posted by till
when i destroyed them the smoke did not come out
You've got a point there, all components that have started to
produce smoke for me have stayed in one piece, while those
who have "rapidly disassembled" themselves have not produced
any smoke.
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Old 22nd May 2004, 01:04 AM   #10
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Quote:
Here in Sweden we say "no smoke without fire", so I guess
transistors glow too if there is smoke inside them, but we
cannot see it.
there is!

you need: a small transistor like BC546 etc, a Märklin Transformer from toy railway.

The package cracks, it glows inside, then it smokes like hell. you need to tune up voltage slowly. I made this with about 10 or 12 years.

explosions without smoke i had very fine with capacitors.
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