regan
New Member
Posts: 5
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Post by regan on Jan 15, 2022 11:44:08 GMT 12
Hi Thanks for letting me join the forum; I was just after some advice on a radio that has developed a fault. I bought a Clipper model 616 and being new to old electronics I plugged it in to see how it sounded. It sounded fine and I continued using it for a couple of months. I accidently left the power on overnight, with no volume and it now distorts and has low volume. Reading up I have probably damaged the output valve (EL41) but I also opened it up to check all the capacitors as I should have done in the start. The good news is it looks like the electrolytics have been replaced, but some of the capacitors are a long way off from the schematic (assuming I’m tracing the circuit correctly). I have marked on the schematic the differences and added some photos of the caps in question. I think I should replace caps A, B and C to closer to the schematic before trying to get another output tube (EL41’s seem hard to find). Could it be the 2 power filter caps in parallel that have caused the problem? I've added the photos as attachments, I'm hoping the appear. Any advice would be greatly appreciated. Cheers Regan
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Post by Peter Walsham on Jan 15, 2022 12:10:25 GMT 12
Hi Regan
Welcome to the forum.
To put your mind at rest, leaving the radio on overnight should not cause any problems. I suspect the EL41 valve is the cause of the weak & distorted audio. The capacitor values are all OK. Even the 1u8 (in place of a 15uF) capacitor would be OK - but may lead to a wee increase of hum heard.
What I would do, first of all, is to check (assuming you have a multimeter) for a positive DC voltage at the grid of the EL41 output valve (connecting the positive probe of your meter to the junction of the 0.01uF capacitor and the 220kΩ & 10kΩ resistors, and the meter negative probe to the radios chassis (with all the valves fitted back in to the chassis). You will need to 'power on' the radio to carry out the test. If there's any positive voltage present, then turn off the radio, and remove the EL41 valve & carry out the test again. if the positive voltage is still present after the EL41 valve has been removed, the cause of the problem is likely to be the 0.01uF coupling capacitor (which looks like it's the brown capacitor on the left of your under chassis photo. However, If the positive voltage is not there anymore, then the EL41 is faulty & most likely to be 'gassy' and will need to be replaced. You are correct, they are very hard to find these days. EL41 valves can be troublesome beasts at the best of times. However, a EL84 valve can be fitted (along with a valve socket and probable bias (cathode resistor) change).
Peter
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regan
New Member
Posts: 5
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Post by regan on Jan 15, 2022 13:06:46 GMT 12
Thanks for the reply, I'll test it out this evening.
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regan
New Member
Posts: 5
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Post by regan on Jan 18, 2022 22:01:17 GMT 12
Hi
I've finally tested it and it's the valve, I think I'll take your advice and fit an EL84.
Thanks a lot for your help with this.
Regan
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Post by Peter Walsham on Jan 19, 2022 7:35:41 GMT 12
Hi Regan I suspected that it might be the valve. Before making a change to an EL84, put a post up in the 'wanted' section of this forum asking if someone has a good used EL41. There just may be someone who has one available. Unfortunately, I am unable to supply one to you myself. They do come up on ebay - an example is this: www.ebay.com/itm/310663655008?hash=item4854ff2e60:g:rPMAAOSwJgtdeo14 (which is for a CV3889 valve, but it's an direct equivalent to a EL41) however, it's costly, at just over $NZ42:00 (which includes shipping), but it does get you exactly what you need. That particular example is a brand new one, and should be good for a long time. Peter |
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roy51
Society Members
If it ain't broke, fix it anyway
Posts: 94
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Post by roy51 on Jan 19, 2022 19:15:57 GMT 12
Hi Regan
I have some EL41 valves, they are not new but seem OK, You are welcome to have them, I have 3, if you want I’ll send them to you. Text me on 0275 167 507 with your address.
Cheers
Roy
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regan
New Member
Posts: 5
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Post by regan on Jan 20, 2022 11:46:56 GMT 12
Thanks, that would be brilliant, I've sent you a text, let me know if it doesn't come through as messages have been playing up on my phone.
Thanks again.
Regan
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roy51
Society Members
If it ain't broke, fix it anyway
Posts: 94
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Post by roy51 on Jan 27, 2022 18:59:15 GMT 12
Hi Regan
Posted today, sorry for the delay, I have been very busy at work, EL41’s should be with you over the next couple of days.
cheers
Roy
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regan
New Member
Posts: 5
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Post by regan on Feb 3, 2022 16:55:09 GMT 12
Hi Roy The valves arrived the other day and have just had a chance to test the radio, it is back working properly and sounding good. Thank you for that and let me know if I can repay you some time, I'm new new to valve amps / radio's so only have a couple of EF86 valves in the draw, I generally have a lot of random transistors for effects pedals. Thanks again
Regan
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roy51
Society Members
If it ain't broke, fix it anyway
Posts: 94
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Post by roy51 on Feb 3, 2022 18:43:20 GMT 12
Hi Regan
Glad the radio now works well for you
If you need other valves in the future, I have a rather large collection and may have what you need.
I’ll keep your offer of transistors in mind.
Cheers
Roy
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