Distorted left channel Proton 520 Amp

allank · 18th June 2005, 02:36 PM

Hi All

I have a Proton 520 Amp Sound from left channel is slightly distorted.
I noticed transistor Q613 BC640 PNP that drives a Toshiba 2SA1094 heats up in about 4 second it can not be touched its so hot. I measured B= -1Volts, C= -31V
E= -0.3Volts

The right channel transistor Q614 BC640 is fine, measures the following B= + 0.6 Volts
C= - 31Volts , E= + 1.2 Volts.
I don’t have a schematic without it, its pretty hard to find what causes the problem.
I removed both BC640 transistors and swapped them, the problem remains.
Any suggestion
Thanks Allan

herrdahlin · 13th September 2006, 01:41 PM

I have two Proton 520's with similar problems. My conclusion is that the poor-quality pots (volume) and pushbuttons (esp. "loudness") that are to blame. I haven't been able to find a schematic or even a manual either.

18th June 2005, 02:36 PM	#1
allank diyAudio Member Join Date: Dec 2004 Location: Sydney	Distorted left channel Proton 520 Amp Hi All I have a Proton 520 Amp Sound from left channel is slightly distorted. I noticed transistor Q613 BC640 PNP that drives a Toshiba 2SA1094 heats up in about 4 second it can not be touched its so hot. I measured B= -1Volts, C= -31V E= -0.3Volts The right channel transistor Q614 BC640 is fine, measures the following B= + 0.6 Volts C= - 31Volts , E= + 1.2 Volts. I don’t have a schematic without it, its pretty hard to find what causes the problem. I removed both BC640 transistors and swapped them, the problem remains. Any suggestion Thanks Allan

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13th September 2006, 01:41 PM	#2
herrdahlin diyAudio Member Join Date: Sep 2006	I have two Proton 520's with similar problems. My conclusion is that the poor-quality pots (volume) and pushbuttons (esp. "loudness") that are to blame. I haven't been able to find a schematic or even a manual either.

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