Schematic says D75 and D52 are both KB262, which is a dual series diode. Voltage drop through each should be about 1.4v. Are they both (D75+D52) gone? You could get away with either of them, and put a jumper in place of the missing one, then readjust VR3, the TX Freq Adj control. Could use 2 1N4148 diodes in series for each if both are missing.
Thank you for your detailed response, I also have a question on my 148f that it squeals on am after 11 o'clock position only on am with multiple amplified microphones. Just happened out of the blue and can't figured out what happened. If you have any advise please adviseIf your plan is to "lock" the transmit frequency so it can never be adjusted to line up with everyone else on the channel, be sure to check the trimmer pot VR5. This is where the "stock" transmit frequency is adjusted when the clarifier does not control it. If it has become "scratchy" over the years, this could cause your transmit frequency to become terribly random from one keyup to the next. A drop of cleaner, and a few excursions from end to end will usually clear this up. Just listening to the sideband transmit on a second radio will reveal if it adjusts smoothly when turned.
Never underestimate the importance of hearing the result of any adjustment to a sideband radio's transmit side. Way too many ways to accidentally make a SSB radio sound like dog doo on the air. Hearing is believing.
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thank you, i will let you know, much appreciated.If you have no luck, I do believe I have a parts radio with the diodes in it.
I would start checking the mounting screws for the board to the chassis to make sure they are tight and have a clean ground connection.Thank you for your detailed response, I also have a question on my 148f that it squeals on am after 11 o'clock position only on am with multiple amplified microphones. Just happened out of the blue and can't figured out what happened. If you have any advise please advise
Regards
Thanks youI would start checking the mounting screws for the board to the chassis to make sure they are tight and have a clean ground connection.
Thanks I will try thatThe mike amp has its own filter cap on the power for that circuit. It's C18, originally 47uf. Got in the habit of using 470 or 220uf to replace it. Usually clears up this issue.
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