Pye PE80 Cambridge International

[bobskie]

Hi I got this radio a while back and decided to take a look inside today. Upon taking apart it all looks good everything original and untouched(unlike a certain other radio I'm working on). I decided at this point I should test the transformer so I put my ohmmeter across both plug prongs and it read infinite resistance. The tar stuff on the transformer seems slightly melted but that may be how it was put on. I may be missing something though is the radio switched on by the wave change switch? I can't see any other way it could be switched on. Hopefully the transformer isn't broken and I'm just doing something wrong, are there any other tests I can try or other reasons for it to not have continuity?

Cameron

[ms660]

According to a manual I'm looking at the on/off switch is ganged with the tone control switch.

Do you have a schematic?

Lawrence.

[julie_m]

Move your probes to the transformer primary itself and test there.

If you get no continuity, the transformer is shot. Otherwise, if you get continuity, test from each plug pin in turn to the transformer; and then home in on the fault by repositioning your probes.

[bobskie]

Yes I meant to say the tone control, I do have the schematic from the dvd. I did test the primary winding from points past the plug but still didn't get anything. I tried again just there and got a reading of 33 ohms, I think I had the probe on a spot of paint which stopped it conducting. Seems the transformer is ok after all which is a relief, now I just need to figure out why it's not getting a reading across the plug,change some caps and buy a new ef41 valve and it should(hopefully) work. I'll keep the post updated.

Cameron

[bobskie]

While I'm waiting for the new EF41 valve to arrive I thought I would list the caps for replacement. I'm replacing all the hunts and wax capacitors. I have a question about C71,72,77 and 78 all rated at 300V AC. It's the AC bit which I don't know about, would these be X or Y rated capacitors(something like that) or would a standard ceramic 1KV DC do the trick? I haven't replaced any AC caps before so I really don't know. I have noted another strange problem, all the bulbs are blown. What would have caused this? Also should I test the radio out on a dim bulb tester before I replace any caps to ensure there is no serious problem like a transformer issue? Or are there any I should definitely replace first to avoid damage? Just one more question, what wattage of bulb should I be using for the tester on a big radio like this?

Cameron

[Boater Sam]

My golden rule, free to all, is to get the set up and running before replacing ANYTHING, safety being taken into account,
For example, do the resistance tests on the mains and output transformers, inspect the wiring, electrolytic can for leaks, valves in the correct sockets, anything burnt/damaged. Then run it up on a lamp limiter.

Fix anything that is stopping it working and check the audio coupling cap/s at the same time, changing if leaky.
Then let it run a while, checking the voltages around the valves as you listen to the cricket.

I cannot understand the CCC ( Compulsive Capacitor Changing ) reasoning, I think it has wrecked more sets than the compulsive twiddler.

That way you don't go replacing parts only to find the set is not worth repairing and you don't finish up frustrated with a non working set because of a simple human error.

A 60w bulb will be fine, as a rule use a bulb a bit less than the rating of the set but it is not critical.
Sam.

[ms660]

Originally Posted by bobskie

While I'm waiting for the new EF41 valve to arrive I thought I would list the caps for replacement. I'm replacing all the hunts and wax capacitors. I have a question about C71,72,77 and 78 all rated at 300V AC. It's the AC bit which I don't know about, would these be X or Y rated capacitors(something like that) or would a standard ceramic 1KV DC do the trick? I haven't replaced any AC caps before so I really don't know. I have noted another strange problem, all the bulbs are blown. What would have caused this? Also should I test the radio out on a dim bulb tester before I replace any caps to ensure there is no serious problem like a transformer issue? Or are there any I should definitely replace first to avoid damage? Just one more question, what wattage of bulb should I be using for the tester on a big radio like this?

Cameron

C77 and C78 are safety critical so far as electrical safety goes, they should be replaced with Y Class types.

C71 and C72 are not safety critical but I would replace them with ordinary film capacitors that have a DC voltage rating of at least 600 volts.

Scale bulbs used to go for a pastime, just replace them and make sure the mains tapping on the mains transformer is set to suit your AC mains supply voltage.

Can't comment on the lamp limiter, never needed to use one.

Lawrence.

[bobskie]

Thanks for the help, I'll get the new capacitors ordered up. It's strange that every bulb is burst rather than just a couple, could it be a resistor issue or something like that? Maybe just a coincidence.

Cameron

[ms660]

Scale bulbs would be the last thing on the consumers mind because the receiver would still function without them.

At some point in time in your house, all the light bulbs fitted will fail....

Lawrence.

[Station X]

Originally Posted by bobskie

Yes I meant to say the tone control, I do have the schematic from the dvd. I did test the primary winding from points past the plug but still didn't get anything. I tried again just there and got a reading of 33 ohms, I think I had the probe on a spot of paint which stopped it conducting. Seems the transformer is ok after all which is a relief, now I just need to figure out why it's not getting a reading across the plug.

Cameron

Chances are it's a problem with the OFF/ON switch. It may well cure itself once it sees a bit of mains voltage.

Best thing to do in cases like this is first to check the fuse in the mains plug using your meter on ohms range. Then clip one lead of your meter to say the neutral pin of the mains plug. Use a probe on the other lead to work you way round the circuit back to the other pin of the mains plug. That way you'll be testing everything in the primary circuit ie plug fuse, mains lead, voltage selector, any internal fuse, transformer winding and the OFF/ON switch.

[bobskie]

That is very true about the bulbs, I'll replace them and see what happens. That's a good method of diagnosis thanks for the tip Graham, I honestly forgot there was a problem with the mains input! I'll need to try that tommorow.

Cameron