High DC offset on DH-220

schubert · 24th October 2011, 01:08 AM

Hellpp!! I just finished replacing everything on the driver boards (except resistors and a few caps) of my Hafler DH-220. In a rare fit of prudence I checked the DC offset before hooking up speakers, and while the left channel was fine, the right channel had 62V (no, that's not a typo)!!! So I guess all 62V from the power supply is getting to the output somehow - but nothing was smoking, and (unlike the left channel) the output mosfets were cold. Any ideas on how to proceed?

schubert · 25th October 2011, 02:51 AM

Found the main problem - bad solder joint - but now the offset is still high (24.5mV) with the pot pinned to one side. Can anyone tell me which transistor affects the offset? I have extras and can replace the offending part with one of a different hFe.

24th October 2011, 01:08 AM	#1
schubert diyAudio Member Join Date: Sep 2008 Location: Pennsylvania, USA	High DC offset on DH-220 Hellpp!! I just finished replacing everything on the driver boards (except resistors and a few caps) of my Hafler DH-220. In a rare fit of prudence I checked the DC offset before hooking up speakers, and while the left channel was fine, the right channel had 62V (no, that's not a typo)!!! So I guess all 62V from the power supply is getting to the output somehow - but nothing was smoking, and (unlike the left channel) the output mosfets were cold. Any ideas on how to proceed?

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25th October 2011, 02:51 AM	#2
schubert diyAudio Member Join Date: Sep 2008 Location: Pennsylvania, USA	Found the main problem - bad solder joint - but now the offset is still high (24.5mV) with the pot pinned to one side. Can anyone tell me which transistor affects the offset? I have extras and can replace the offending part with one of a different hFe.

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