roy51
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If it ain't broke, fix it anyway
Posts: 96
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Post by roy51 on Oct 31, 2020 17:10:05 GMT 12
Looking for a circuit diagram for a Raycophone 72E Console
A picture of the radio appears in MGA page 64, but is described as a 6 valve TRF with twin speakers.
The radio I have is 7 valve, definitely not a TRF and has the following valve lineup:
35/51, 57, 56, 58, 56, 47 and 80. It has twin speakers and the cabinet is identical.
It is a BC only radio
Any help would be appreciated. I have searched the net for more info on this but have drawn a blank.
The radio is going, I have replaced all caps and a couple of out of tolerance resistors, but there is distortion when the volume is turned up. The volume control appears to control the bias to the early stages (RF)
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Post by Richard on Nov 2, 2020 11:55:23 GMT 12
A circuit diagram would be good to look at. I suspect the audio detector circuit is your problem and I suspect your radio uses "plate detection" ? have a look at this article: messui.polygonal-moogle.com/valves/SC199601.pdfEarly radio was mainly talking and very little music, the detector circuits weren't well designed, so distortion did exist but not as noticeable with talking. The coupling capacitor after the detector in later circuit designs could also be a problem if it became charged due to DC from the detected signal, which in turn causes distortion. Have a look at this article: messui.polygonal-moogle.com/valves/VR199603.pdf
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roy51
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If it ain't broke, fix it anyway
Posts: 96
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Post by roy51 on Nov 4, 2020 7:11:20 GMT 12
Thanks Richard I'll have a look at those sights , at present I am stripping down the chassis for a complete restore as it was originally painted silver but has now turned some what rusty.
Reading the first article is exactly what my problem is. The radio sounded reasonable on speech but music was absolutely horrible. The anode bend detector valve in the Raycophone is a 56, so the modification as in the article should be easy to implement.
Once I have re-built the chassis I will give it a go.
Still no luck with a circuit diagram however.
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roy51
Society Members
If it ain't broke, fix it anyway
Posts: 96
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Post by roy51 on Oct 7, 2021 11:30:00 GMT 12
Hi Richard
Re-built the radio, same horrible distortion on music, so decided to do the diode mod as per your references last time. Works an absolute treat, music and speech much improved. Thanks for pointing me in the right direction. Now for the cabinet, which I will strip down and re-do.
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