29th Nov 2022, 11:38 am | #1 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,731
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Vidor CN349
Hi,
I am currently working on restoring the above set. Hopefully someone can give me some tips... OK, so far, replaced all electrolytics and waxies. New rectifier valve as it was dead, the others all appear OK. Audio amp working lovely. Oscillator is running and the set does tune, BUT, lots of screams and whistles everywhere. Can only really tune into one station carefully on MW. Checked IF alignment which is fairly spot on. Sometimes when tuning it appears to get only one sideband, as some stations sound a bit donald duck. I SUSPECT the IF stage centred around the EF39, as the slightest touch of alignment in L15/L16 can cause it to widely oscillate. I have tried a replacement EF39. Any pointers gratefully received. Many thanks, Adrian. |
29th Nov 2022, 2:10 pm | #2 |
Nonode
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,364
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Re: Vidor CN349
Hi Adrian, has the replacement EF39 got a fully intact coating of red metallised paint, and is it making good contact with the earth pin wire that should be poking up a mm or so above the top rim of the valve skirt? Jerry
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29th Nov 2022, 2:58 pm | #3 |
Nonode
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,364
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Re: Vidor CN349
If the valve coating is OK, also check that the chassis connection to pin 1 (M) of the valve holder is OK.
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29th Nov 2022, 3:02 pm | #4 |
Octode
Join Date: Sep 2020
Location: Thetford, Norfolk, UK.
Posts: 1,731
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Re: Vidor CN349
Top marks to Jerry. Many thanks.
The valve looked perfect unlike the original, but just checked and the screen was O/C. I have wrapped the original in foil and the fault has disappeared. Thanks again! |
29th Nov 2022, 7:49 pm | #5 |
Nonode
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,364
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Re: Vidor CN349
Nice work. A good source of replacement for EF39 is the ex-miltary spare CV1053. These seem fairly plentiful and reasonably priced, and the light grey/silver metallisation survives much better than the red Mullard jobs. That said, the latter can usually be rescued using the bacofoil trick, as you have done. Doesn't look pretty but saves the valve. Cheers, Jerry
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