Problems with valve radio

Loss of HV at a guess...rectifier tubes can fail, resistors fail, caps fail etc, etc

There are plenty of Youtube videos with good information on servicing valve appliances.

Best advice really, is that if you are not confident around modest voltages (150-300v) then find someone who is :)

In the early 60s I fixed our old wartime Ministry of Supply radio by replacing the diode, which had failed, and there was a lead from a tetrode that had come adrift from somewhere so I soldered it to the HT line. It worked well enough after that.

The diode going o/c would be enough to mean nothing at all from the speaker.

Yes. Although the length of time it will glow for if the vacuum inside the envelope has deteriorated is severely limited. Usually it is old HT capacitors that tend to give up the ghost first - sometimes by dripping flaming wax onto the floor so don't leave it unattended!

Most likely power supply related. Usually there is a huge hum, but if the capacitors shorted out then maybe the ht fuse has gone. For something like this, if you really do want it to work, be prepared to let a specialist have it for at least a couple of months and a big bill. The trick with old gear is to use them at least once every few months. I have done this with a Rogers amp and its still working from 1965. Brian

Yes indeed. One fairly safe thing to do is to carefully remove each valve from its holder. There could be screening cans and spring retainers, then a squirt of contact cleaner in the holes and a wipe over of the pins. Do them one at a time, and wiggle them as they go in. When all done try it. Probably be a waste of time, but you might at least have some life indications from that. As I said before though, if the ht fuse has gone then its probably really a job for a competent engineer. Brian

Or exploding electrolytic leaving foul smelling bits of debris everywhere for months. I did this with an uncased tv once, my mother was not pleased. Brian

Don't spray with contact cleaner! Some valve bases were made out of poor quality paxolin/tuffnel and the contact cleaner can cause the HT to track across with a possible fire. This was very apparent on some "vintage" Ferguson Radiograms with the valve bases and waveband selection switch. I remeber them well from my apprenticeship days.

At that age most of the capacitors, both paper and electrolytic will have dried out and failed. Without replacing these any other fault finding is futile. "Recapping" (replacing all the wax paper and electrolytic capacitors) is fairly straightforward if you have soldering skills and modern replacement components are cheap and physically a lot smaller than the old ones so there is usually space to fit them in. There is no guarantee that this will cure the problem but it usually does.

If you don't have moderate skill with a soldering iron and working on old radios you may have to go hunting an aged wireless repairer, there are still a few about.

Yes. What do you mean by "glow"? A redish glow from deep inside the metal work inside the valve or a dim purple/blueish glow around the metal work?

The redish glow is the heater, required to release electrons from the cathode. The blueish glow has various sources and isn't generaly a problem but does indicate that the HT is present. Not having ablueish glow doesn't mean there is no HT.

As others have said, inspect the thing looking for obviously burnt/failed parts. Reseat the valves, no contact cleaner. The getta on the inside of the glass envelope (probably at the top) of each valve should be silvery and can be quite a dark silvery. If it's white air has got in and the valve is useless.

If you do try removing the valves, grip them by their bases if they have them, rather than by the glass envelope, as the glue holding the envelope to the base gets brittle with the heat and over time, and you may find yourself holding the envelope with a bundle of broken wires sticking out of the bottom, and the base still firmly in its socket. DAMHIKT.

I'd start by checking the HT supply. But as others have said most of: HT is 100s of volts. You need basic comptence to play with it There will be capacitor failures that need fixing to avoid further damage Many old valve sets were transformerless live chassis sets, again you need to understand the issues with that.

Valves are usually replaceable or repairable. More likely to be faulty elsewhere.

NT

The first thing to do with an old valve radio is to not turn it on - IIRC a particular capacitor which is very likely to have gone bad can blow the output transformer and then you're screwed.

I'd start by checking the HT supply. But as others have said most of: HT is 100s of volts. You need basic comptence to play with it There will be capacitor failures that need fixing to avoid further damage Many old valve sets were transformerless live chassis sets, again you need to understand the issues with that.

Valves are usually replaceable or repairable. More likely to be faulty elsewhere.

NT

For a really spectacular effect have the Selenium rectifier in some old sets fail. The smell stays until you sell the house which you usually have to do after about 6 months when you realise the aroma is never going to fade.

I dunno. I think I finally discovered the last piece of cat urine soaked hpouse te day before yereday - the MDF riser for the bottom stair tread.

Now replaced with a car body filler frontage in case.

Wot he said about don't switch it on - output transformer likely to fail quickly so no sound at all and lots of expense getting it re-wound....

Look at

Well Graeme, you seem to have attracted a large number of well meaning but pretty useless entities.

Have you a DMM? If you haven't stop now, there is little point continuing.

Look at the valves, dont pull two out at once, and write down the valve numbers. If the valves have metal top caps, stick the thing on Ebay, it's full of people wanting to make easy money.

Stick the valve numbers in a post and I will provide you with details of the expected voltages and where to prod a wet finger. This will be sufficient to trace most faults, although an Xtal earpiece and a small

AB

Ah. Not much use then. As the very first check would be to make sure the HT is present and correct.

or replace with a few watt mains transformer.

you can also get help here or in news:sci.electronics.repair

NT