I am working on restoring a KR-4400. I have finished re-capping all of the electrolytic capacitors (including the filter CAPs). I measured for DC Offset before I started. I got 40.5 mV on left channel and 10 mV on right channel. I recapped the unit and reset the bias voltage to 30 mV for each channel. The DC offset was still the same. I replaced the differential pair transistors (Qe1-4) with new matched KSA992F transistors. The hFE gain on the new pairs was around 470. The left channel improved to 18.5 mV and the right channel improved to 5 mV. Any suggestions on what to look for to improve the left channel DC offset?
Trouble shooting DC Offset in Kenwood KR-4400
- Thread starter Kbob1001
- Start date
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Leave it as is. 18.5mv is good. They don't have to match.
Most say that anything under 50mv will be fine.
Thanks for the feedback. I did some reading tonight on some other posts about this issue. They said anything from 16 mV to 50mV was acceptable. This is my first time trying to work on restoring a vintage receiver. I have learned a bunch so far. I wasn't quite sure if this was an issue that needed more investigation. The feedback from the community here is great. Thanks again.
Anything from 0mv to 50mv. 0mv would be ideal.
I'm new at this too. xraytonyb has some excellent videos on electronics. I have a KR-5400 and he has an entire series that goes through the receiver step by step.