Mega Tracker CB1100 CB27/81 UK FM CB radio - Pt 2 of 2 not fixed rx IF snag.
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- Опубліковано 15 тра 2024
- Well this has been a swine of a job & untimately I've failed to fix one of the RX problems with the 455Khz IF, resulting in deaf receive coming in at 7uV for 12dB SINAD (Should be 0,4uV). The radio came in with no rx owing to VCO setup. After that it was 100uV receive. Changing all three filters...all provided some improvement, brought us to 10uV but with very strange AGC action. Changing the FM IF subsystem chip (MC3357) corrected that & that's as good as I've managed to get it. No service info, bits & pieces here & there & differences between this set & my own sample set really don;t help.
At least I sorted the VCO out & the transmit thermal runaway. No transmitted audio was a duff electrolytic capacitor around the Plessey VOGAD speech processor chip....and also an open circuit RF choke on the microphone socket input. Afther that it was putting wiring back that was missing from the speaker to the main board...and discovering the dodgy external speaker socket.
Spoiler alert...we did just about manage the full 6-miles on the 'on the air' test I've just recorder & will be posted tomorrow.
Perhaps if used with a preamp, the set would work OK.Remember...transmit is spot-on. Receive is deaf.
Recorded 14, 15, 16th May 2024
Richard G0OJF
Lincolnshire, UK
(C) Tango Systems Group 2024
rshireby@yahoo.co.uk - Наука та технологія
Exceptional reception around ‘not so’ scratchy corner. Love the Robin at the end too.
A big task that one will be an interesting Scratchy corner test.
hi 👋 richard good luck repairing the mega tracker cb 1100 cb 27/81 uk fm cb radio from paul chapman at east sheen 73's
Thank you Paul,
Richard
@@ukfmcbradioservicingTango21 to richard you are most welcome can you please tell me when is the air test please 🙏 from paul chapman at east sheen 73's
Tomorrow morning at 9AM Paul.
@@ukfmcbradioservicingTango21 ok richard cheers 🍻 from paul chapman at east sheen looking forward to see the air test