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Old 1st May 2007, 10:34 AM   #1
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Default Thermal Cut-off Temperature for a VFET

Have a Sony TA-4650 integrated VFET amp, with a blown PTC thermistor (PTH401 on the schematic). I've no idea at what temperature that the original is supposed to operate. Got choices of 30C to 110C, and was thinking that 60C ought to be reasonably close to a proper temperature to disconnect the load.

Think that's too hot?
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Old 1st May 2007, 11:25 AM   #2
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Default Re: Thermal Cut-off Temperature for a VFET

Quote:
Originally posted by EchoWars
Have a Sony TA-4650 integrated VFET amp, with a blown PTC thermistor (PTH401 on the schematic). I've no idea at what temperature that the original is supposed to operate. Got choices of 30C to 110C, and was thinking that 60C ought to be reasonably close to a proper temperature to disconnect the load.

Think that's too hot?
85C PTC
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Old 1st May 2007, 09:13 PM   #3
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Is that a guess, or is there a reason to pick that temperature?
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Old 2nd May 2007, 01:15 AM   #4
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Where is the PTC located(stick to what material)???
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Old 2nd May 2007, 02:58 AM   #5
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PTC is screwed to the output transistor heatsink. Guess I didn't make that clear in my first post.
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Old 2nd May 2007, 11:25 PM   #6
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Hmmm...thought this would be an easy subject. 100+ views, 1 terse reply, 1 question.

Thermal devices have been around for years...most amps with fans have a switch to start the fan at about 70C, so obviously semiconductor destruction isn't going to happen at that temp. I was simply hoping that someone might have some experiance with maximum safe operating temperatures for power devices.

Talking to myself again...I'll toss a 70C PTC in there (tolerance on the only ones I can find is +/-7C) and call it a day.
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