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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 15th Dec 2018, 2:47 pm   #1
Davewantsone
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Location: Wigan, Greater Manchester, UK.
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Default Roberts R66 - Local Oscillator Transformer

I recently bought a marooon coloured R66. After replacing a few capacitors and the rectifier diodes I powered it up first via a variac. It was completely dead on MW but worked brillantly on RTE LW and nothing else!
Further investigation I discoved the L.O.coil L7 was open circuit.
I decided to remove the can and dismantle it. The L7 winding is under the L5 winding. So I decided "how about putting a new winding on top of L5 in place of L7"? I measured L8 resistance (about 6 ohms) and thought the new winding would probably have less turns . So I picked around 4 ohms. I found some insulated copper wire of around the same diameter and after lifting the 2 capacitors in the can wound the coil on top of L7 and soldered the connections to the place that L7 would go. I resoldered the capacitors and put everything back in the can. I then resoldered the connections back into the radio.
I then switched the radio and was rewarded straight away with R4 on LW. I switched over to MW and that was now working properly with loads of stations and all I needed to do was a slight tweek of the trimmer capacitor to align the HF end of MW.
I now have a very nice looking and sounding R66

Last edited by Davewantsone; 15th Dec 2018 at 2:59 pm.
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Old 15th Dec 2018, 5:21 pm   #2
ukcol
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Default Re: Roberts R66 - Local Oscillator Transformer

Don't you love it when a plan comes together.
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Old 20th Dec 2018, 11:08 pm   #3
JayBee66
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Default Re: Roberts R66 - Local Oscillator Transformer

I too bought a maroon R66 with the same fault. Picked up RTE and a few French stations but nothing on MW.

The same open circuit on the coil. A common fault or just coincidence?

https://www.vintage-radio.net/forum/...d.php?t=131898

Thanks for the solution. I suppose I'll get round to it, someday.
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