Thermal Cut-off Temperature for a VFET

EchoWars · 1st May 2007, 10:34 AM

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 30°C to 110°C, and was thinking that 60°C ought to be reasonably close to a proper temperature to disconnect the load.

Think that's too hot?

Workhorse · 1st May 2007, 11:25 AM

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 30°C to 110°C, and was thinking that 60°C ought to be reasonably close to a proper temperature to disconnect the load.

Think that's too hot?

85°C PTC

EchoWars · 1st May 2007, 09:13 PM

Is that a guess, or is there a reason to pick that temperature?

Leolabs · 2nd May 2007, 01:15 AM

Where is the PTC located(stick to what material)???

EchoWars · 2nd May 2007, 02:58 AM

PTC is screwed to the output transistor heatsink. Guess I didn't make that clear in my first post.

EchoWars · 2nd May 2007, 11:25 PM

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 70°C, 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 70°C PTC in there (tolerance on the only ones I can find is +/-7°C) and call it a day.

1st May 2007, 10:34 AM	#1
EchoWars diyAudio Member Join Date: Dec 2002 Location: Left of the Dial	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 30°C to 110°C, and was thinking that 60°C ought to be reasonably close to a proper temperature to disconnect the load. Think that's too hot?

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1st May 2007, 09:13 PM	#3
EchoWars diyAudio Member Join Date: Dec 2002 Location: Left of the Dial	Is that a guess, or is there a reason to pick that temperature?

2nd May 2007, 01:15 AM	#4
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	Where is the PTC located(stick to what material)???

2nd May 2007, 02:58 AM	#5
EchoWars diyAudio Member Join Date: Dec 2002 Location: Left of the Dial	PTC is screwed to the output transistor heatsink. Guess I didn't make that clear in my first post.

2nd May 2007, 11:25 PM	#6
EchoWars diyAudio Member Join Date: Dec 2002 Location: Left of the Dial	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 70°C, 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 70°C PTC in there (tolerance on the only ones I can find is +/-7°C) and call it a day.

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