Technics SU 8055 wierd problem

sewerwisp · 9th December 2010, 05:39 PM

I have the above integrated amp, I recapped it and re resistored. Cranked it for two weeks. I mean I just played it aggressively. Worked great, then...
left channel crackles when powered up, UNTIL, both storage caps are charged. Both have around 42 volts DC across them when fully charged.
Right channel works fine. The left crackles when chargeing, then stops when fully charged. Crackles when dischargeing as well.
Left has a hard time dischargeing, but right dis charges quickly.

Stumped for now. I would like to attach part of schematic I think is at fault.
Will do that tonite if possible.

Thanks, Tom

Tekko · 9th December 2010, 05:58 PM

Sounds like you need to set bias for left channel. Assuming your talking about power supply capacitors discharging.

sewerwisp · 17th February 2011, 12:32 AM

the bias in the bad left channel is almost a volt off. A few mv on the right,
but the left is stuck at around -0.8v, and cannot be adjusted.

i tried swapping the main amp chips, no change.

9th December 2010, 05:39 PM	#1
sewerwisp diyAudio Member Join Date: Sep 2008	Technics SU 8055 wierd problem I have the above integrated amp, I recapped it and re resistored. Cranked it for two weeks. I mean I just played it aggressively. Worked great, then... left channel crackles when powered up, UNTIL, both storage caps are charged. Both have around 42 volts DC across them when fully charged. Right channel works fine. The left crackles when chargeing, then stops when fully charged. Crackles when dischargeing as well. Left has a hard time dischargeing, but right dis charges quickly. Stumped for now. I would like to attach part of schematic I think is at fault. Will do that tonite if possible. Thanks, Tom

17th February 2011, 12:32 AM	#3
sewerwisp diyAudio Member Join Date: Sep 2008	bias the bias in the bad left channel is almost a volt off. A few mv on the right, but the left is stuck at around -0.8v, and cannot be adjusted. i tried swapping the main amp chips, no change.

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9th December 2010, 05:58 PM	#2
Tekko diyAudio Member Join Date: Jan 2005	Sounds like you need to set bias for left channel. Assuming your talking about power supply capacitors discharging.

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