ptbm121d4x Low Power

This is the place to discuss any general CB radio related topics. Getting started, installations, operation etc.
bozzy
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Location: York

Re: ptbm121d4x Low Power

Post by bozzy »

The seller I got the fakes from offered a refund straight away when I sent them the picture above.

Anyway, I finally have this radio working again at full power now on FM and AM, but SSB is very low despite maxing out the modulation and injecting a 2.4khz tone at 10mW during alignment.

Think next step is the Audio IC chip TA7205P?
Edd200sx
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Call Sign: AMC45

Re: ptbm121d4x Low Power

Post by Edd200sx »

You’ve done the alc mod?
bozzy
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Joined: 19 Aug 2016, 21:34
Location: York

Re: ptbm121d4x Low Power

Post by bozzy »

Thanks for that.

I have just done the R150 and R28 cap mod, it has squeezed out 1 extra watt on SSB, I am told my audio is better on FM too.

Still very low though on ssb, 4 watts max on ssb with test signal injection but getting max power on FM, even had to back off the alc a bit as it was pushing 16W.

Seems I still have an issue with ssb modulation.....
bozzy
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Posts: 125
Joined: 19 Aug 2016, 21:34
Location: York

Re: ptbm121d4x Low Power

Post by bozzy »

OK, I have changed the audio chip, SSB is max power now.

Not happy that FM is pushing 15W, so modified the mode switch wiring so FM is limited the same way as AM (see other post).

Noticed some other suggested modifications to try, will do them, then go full through full alignment again, think I am getting there now.

Regards
Bozzy
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