upd858 Ferris 5500 (Robyn 520d) SSB distortion on RX and TX

[QHL214]

Hi everyone. I have an Australian version of the Robyn 520D (a Ferris 5500) which has distorted RX and TX audio on SSB only. AM is fine. I have completely recapped the radio and aligned it using the TRC-449 service manual. I guess it might be a problem in the IF stages or BM but all IC and transistor voltages are fine in those areas. This is an 858 radio and in great condition and worth saving. Anyone got any ideas? Many thanks. James

 

[loosecannon]

you might try probing the AGC buss and look for a negative going DC voltage.
probably around 1 or 2 volts.
this voltage should lower as stronger signals are fed into the antenna jack.
LC

 

[QHL214]

Thanks for that loosecannon. I’ll check it out.

 

[WP4AFB]

I'm trying to get a Robyn 520D and your comment help me get these. I'll use it to work on mine.