Realistic TRC-457 (858 SSB Chassis) recapped, worked fine for a few weeks, now squealing on SSB only.

[Osscott]

Hoping someone smarter than I, can assist with diagnosing this high pitched tone i get when TX on SSB. Does not happen on AM.

Symptom: When TX on SSB, a high pitched squeal like tone is heard on the RX of other operators.

Troubleshooting:

changed mic and same thing. keyed up radio with no mic by shorting the TX and ground pins on the mic connector on the radio. same squeal with no mic!

reduced ALC and MIC GAIN potentiometers to their lowest values. No change in squeal.

however, when I modulate, the squeal stops, but sneaks in between my words.

checked the caps recently replaced in the TX audio section. All tested within tolerance.

performed the unit 399 audio mod (D23 was a 220 ohm resistor) replaced with the recommended diode. tested diode - ok. also replaced the 2.2uf 10v cap with a 10uf 25v cap. cap tested ok.

I saw this post https://www.worldwidedx.com/threads/uniden-858-ssb-cb-squeal-on-am-transmit.255532/ which is similar to my issue but this one appears to only happen on AM. Thinking of giving it a try.

Anyone ever come across this issue? Would appreciate any guidance or advice.

Thank you!

 

[Osscott]

Hoping someone smarter than I, can assist with diagnosing this high pitched tone i get when TX on SSB. Does not happen on AM.

Symptom: When TX on SSB, a high pitched squeal like tone is heard on the RX of other operators.

Troubleshooting:

changed mic and same thing. keyed up radio with no mic by shorting the TX and ground pins on the mic connector on the radio. same squeal with no mic!

reduced ALC and MIC GAIN potentiometers to their lowest values. No change in squeal.

however, when I modulate, the squeal stops, but sneaks in between my words.

checked the caps recently replaced in the TX audio section. All tested within tolerance.

performed the unit 399 audio mod (D23 was a 220 ohm resistor) replaced with the recommended diode. tested diode - ok. also replaced the 2.2uf 10v cap with a 10uf 25v cap. cap tested ok.

I saw this post https://www.worldwidedx.com/threads/uniden-858-ssb-cb-squeal-on-am-transmit.255532/ which is similar to my issue but this one appears to only happen on AM. Thinking of giving it a try.

Anyone ever come across this issue? Would appreciate any guidance or advice.

Thank you!

Well it appears the SSB balance was out of whack, which was odd because i had aligned that when i completed the recapping. dont know why it needed to be realigned again. perhaps it was inadvertently moved.

anyway. all good now.