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Old 7th Jun 2008, 9:17 pm   #1
paolo67
Retired Dormant Member
 
Join Date: Jun 2008
Location: Milan, Italy
Posts: 15
Default Racal RA17L BFO behaviour

Hi everybody,

here is Paolo from Italy, I just discovered the forum. I'm in the process of repairing and aligning my RA17L. I already went through IFs, 37.5Mhz filter, first and second VFOs, and the preselector. I found several leaking capacitors among the paper type and resistors that raised to more than 100% in value. The calibrator was completely non-working. I did not yet touch the quartz and 100kHz filters, and just left the 40MHz strip alone...

I' quite satisfied up to now, however one thing that makes me thinking is the BFO: when I switch it on, the meter jumps nearly at full scale. So I thought it must inject too much power into the detector. Then, I connected the spectrum analyser at pin 7 of valve V21, and I found 100kHz harmonics up to more than 5MHz, all almost equally powerful up to 1MHz and then progressively reducing. Everything goes if I switch the BFO off.

Do you think this behaviour is normal? It would explain the extra power.

The BFO control works and the trimmer does as well. All harmonics shift when adjusting the control or the trimmer.

Also, I found that dismounting the BFO unit it is not easy especially because of the three wires underside. I did not try yet... maybe someone found a more clever way of servicing it?

Thanks for reading, any help is appreciated.
Paolo
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