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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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23rd Oct 2018, 10:23 pm | #21 |
Nonode
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,384
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Re: Cossor melody maker 501AC
As mentioned here is a pic of the spare valves that I hold for this set; from left to right ECH35 (OM10), EF39 (OM6), EBC33 (OM4), Brimar 6V6GT, Cossor 6V6G, EZ35 (6X5G). You have a PM.
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24th Oct 2018, 11:09 am | #22 |
Tetrode
Join Date: Sep 2018
Location: Inverness, Scottish Highlands, UK.
Posts: 74
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Re: Cossor melody maker 501AC
I stripped the IF tranny last night - coils reading 10 ohms and caps 100 nF as they should. No leakage evident in the caps either. I’ll try aligning again once the valves come from cathoderay57.
Also checked all the little square caps with one leg lifted - no leakage (Gohm range readings) at 100 vdc. |
24th Oct 2018, 1:14 pm | #23 |
Banned
Join Date: Dec 2013
Location: Middlewich, Cheshire, UK. & Winter in the Philippines.
Posts: 3,897
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Re: Cossor melody maker 501AC
The Cossor 500 series chassis is let down by the bottom coupled aerial coil.
I have several and most work to a good standard, not outstandingly sensitive. One however is terrible and its the aerial coil that is at fault. Why I cannot establish, it looks and measures resistance wise the same as others, obviously something is amiss with its Q. I would attempt to rewind it but it is difficult to establish the internal connections as the winding ends disappear into the hollow center and the fine wire is buried in the wax. If the set was more desirable I would try to redesign the front end with new coupled aerial coils. |
24th Oct 2018, 4:17 pm | #24 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Cossor melody maker 501AC
Some stuff about bottom end coupling in this article:
http://www.vintageradio.me.uk/radcon...mage/jan55.pdf Lawrence.. |
24th Oct 2018, 4:58 pm | #25 | ||
Dekatron
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,082
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Re: Cossor melody maker 501AC
Quote:
Quote:
It also has simple AVC, about as basic as you can get, even though it does have a double-diode triode. The DAC90a has delayed AVC, giving better sensitivity with weak stations. Its saving graces are that it has a good-size loudspeaker, and a good robust output valve (6V6 or equivalent). It has a mains transformer so runs cool. And it's dead easy to service, with everything well-spaced and accessible. Looking forward to news on the IFT! |
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24th Oct 2018, 6:44 pm | #26 |
Tetrode
Join Date: Sep 2018
Location: Inverness, Scottish Highlands, UK.
Posts: 74
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Re: Cossor melody maker 501AC
Kalee20 - see above. I stripped the IFT and found no faults. Not sure why the top screw wouldn’t tune, but I report back once the new rectifier arrives.
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30th Oct 2018, 6:07 pm | #27 |
Tetrode
Join Date: Sep 2018
Location: Inverness, Scottish Highlands, UK.
Posts: 74
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Re: Cossor melody maker 501AC
Right - valves arrived yesterday from Cathoderay57.
Swapped the knackered rectifier 6X5G for the NOS Elpico EZ35, and all the voltages jumped up to what they should be... Except for V3 (OM-4, detector/preamp) whose anode voltage was too high. Swapped in the replacement and volume and general performance improved dramatically. Fitted a 3-core, twisted flex with a nice bronze cloth outer. Aligned and reassembled. It’s now sitting in the bedroom - reception is reasonable, although with some static in the background. Not sure if this is normal for these old things or not. On SW there’s still some motorboating, but I never use that anyway. Thanks all, especially Cathoderay57! |