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

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Old 26th May 2020, 7:43 pm   #1
regentone001
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Default Regentone A353

I am having a brain freeze and can't remember what causes this problem.
I have replaced all the waxies and with the aerial in the aerial socket the set works but is very quiet. But once the aerial is attached to the top cap it bursts into life and is very sensitive on all the wavebands.
Please put me out of my misery and tell me what I am missing
Thanks
Steve
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Old 27th May 2020, 9:16 am   #2
cathoderay57
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Default Re: Regentone A353

Hi Steve, from your mention of "connecting an aerial to the top cap" it sounds like you have the early version of the set with the following valves ECH35, EF39, EBC33, 6V6G, AZ31. If that is the case the following possibilities should be considered. I'm referring to Trader Sheet #997 (which also covers the AC/DC version as well as the later variants with miniature valves which makes it all a bit confusing). First option is to look for a fault in the aerial feed circuit. Principal candidate is C1, a 0.02uF capacitor connected between the aerial socket and the aerial coils. If it has lost capacitance or turned into a high value resistor it won't help. Second you could have an open circuit aerial coupling coil L2. Third option is a low-gain ECH35. Either try a replacement valve or check the voltages. The Trader sheet quotes for the later circuit using a 6C9 mixer/oscillator instead of an ECH35 but the voltages should be in the same ball park. The Trader Sheet quotes voltages measured with an Avo Electronic Test Meter so should be close to what you should measure. Mixer anode 250v, Grid 2/4 84v and the oscillator anode 60v. Hope that helps as a starter for 10. Cheers, Jerry
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Old 28th May 2020, 1:54 pm   #3
regentone001
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Default Re: Regentone A353

Hi Jerry thanks for the response, I had tried another ECH35 from a working set to no avail. So I started taking the voltages as you suggested. They all appeared a bit on the low side, even the AC from the transformer, until I realised that there is an additional 9volts due to the set using common biasing, adding that on brought all the voltages up to about right. But and its a big but, as I was doing this my eyes fell on the trimmers and I noticed that the oscillator side had wax seals on them there was nothing on the aerial ones. Yup the phantom twiddler alias screw tightener had been playing and all of the aerial trimmers had been tightened down. Tuning the set to a station with the aerial attached to the top cap and then moving it to the aerial socket and adjusting the trimmer brought medium wave up nicely. Then I did the same with long wave. short wave I will do when I have replaced all the waxies in my signal generator.
Thanks
Steve
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Old 28th May 2020, 3:23 pm   #4
cathoderay57
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Default Re: Regentone A353

Nice work, well done. When you said sensitivity was down on all 3 bands, I thought it would be unlikely that all 3 aerial trimmers would be out. Just goes to prove that we should never underestimate the Phantom.......
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Old 4th Jun 2020, 8:47 am   #5
Phil G4SPZ
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Default Re: Regentone A353

Quote:
Originally Posted by regentone001 View Post
...my eyes fell on the trimmers and I noticed that the oscillator side had wax seals on them there was nothing on the aerial ones. Yup the phantom twiddler alias screw tightener had been playing and all of the aerial trimmers had been tightened down...
I think we often give in to the temptation of diving in with the meter prods before we’ve exhausted all the more obvious signs. You fixed this radio using nothing more than your eyes and ears, so it’s a good message to send out that an awful lot of faults in vintage electronics can still be diagnosed visually.

It’s also wise to remember that, to paraphrase Sod’s Law, “If a thing can be twiddled, it probably will have been” and there’s more than one thread currently running on the Forum where The Phantom has been at work!
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