PYE P45 stopped making sound.

[Tom Stone]

Hi, wondered if any of you knowledgeable Ladys & Gents can offer me some advice.

I have had a PYE P45 displayed for a number of years and have recently got it down to give it a good clean. I remember when it went onto the shelf it was working but now when turned on everything works, lights come on but absolutely no sound whatsoever, not even a hissing or clicking. Have inspected the speaker and connections but can see anything out of place. I remember asking advice before on the forum concerning one of my other radios that had the same problem and was advised to change one of the valves, doing this resolved the problem. Would anyone know what valve on this set is connected with sound production?.

ECH42 EBF80 EL41 EZ40

Sorry, not very technical but can change a valve.

Thanks, Tom

[Station X]

This set has a pick up socket.

Turn the waveband selector to GRAM, turn the volume right up and touch each connector of the pickup socket in turn with a metallic object such as a screwdriver.

A loud hum or buzz will indicate that the power supply and output valve are working correctly.

[Radio Tech]

Hi Tom

If you have got the circuit diagram, check through the circuit starting with the power supply, here you need to make sure that firstly the heaters of all valves are lit, then check to see if you have HT voltages off the cathode of the rectifier and on the anodes of each valve. The other thing is check the continuity of the output transformer and make sure the loudspeaker is not open circuit or disconnected from the set in some way. Hope this will give you a starting point in helping you solve the problem.

Best wishes

Ken

[G8HQP Dave]

Is there any hum? This (and other Pyes) are known for magnetic coupling between the mains transformer and output transformer, giving a little speaker hum even before the valves have warmed up.

Unlike most other sets, you won't get much hiss from the audio stages as there is no audio voltage amplifier valve in this design. Any hiss has to come from the radio section. Because of this, you need all valves working to get any sound (apart from hum).

[Station X]

Originally Posted by Tom Stone

Sorry, not very technical but can change a valve.

Originally Posted by Radio Tech

Hi Tom

If you have got the circuit diagram, check through the circuit starting with the power supply, here you need to make sure that firstly the heaters of all valves are lit, then check to see if you have HT voltages off the cathode of the rectifier and on the anodes of each valve. The other thing is check the continuity of the output transformer and make sure the loudspeaker is not open circuit or disconnected from the set in some way. Hope this will give you a starting point in helping you solve the problem.

Best wishes

Ken

I think that if the OP is going to go down this route he'll need a bit more detail. Does he know which valve is the rectifier? Where does he connect his meter, assuming he has one? Which pins are the anodes of the valves? Are the expected voltages AC or DC and of what magnitude?

[Radio Tech]

Hi Tom

Sorry, I should have realised about your experience, looking at the back of the set V4 nearest the mains transformer is the rectifier, underneath pin 1 starts from the pip on the valve and its pin 7 which is the cathode of that valve, the anode of the output valve V3 is pin 1 and V2 anode is pin 6 and V1 the first valve looking at the rear of the set its anodes are pin 2 and pin 3. The main smoothing capacitor is that one positioned right in the corner when the chassis is viewed from above, view this capacitor from underneath of the chassis and you should find a resistor soldered across the terminals of the capacitor, this may be open circuit, if the rectifier is doing its job you should find by measuring with a suitable meter (AVO) set on 300V range a DC voltage of 275V on the cathode.

And welcome to our forum

Best wishes

Ken

[Stylo N M]

To answer one of the OP's questions, in layman's terms the EL41 would be the valve that is in direct connection with the sound output. Although a fault in any of the valves could result in no sound being present.

Paul.

[Tom Stone]

Hi everyone, fantastic, what a fount of knowledge you all are. Yes, now have resolved the problem, in the end it was a simple fix as I just replaced the EL41 valve and hay presto, I have sound.

Thanks again to everyone for the info, absolutely fascinating although half of it I didn't understand but hopefully one day I will.

All the best, Tom

[Boater Sam]

Good. Glad it now works but you need to consider replacing the EL41 grid 1 coupling capacitor, its leakage is possibly what killed the original valve. You risk another one or the transformer failing if it is leaky. Its often referred to as 'that capacitor'

[Cobaltblue]

That's interesting.

Valves rarely fail completely dead like that as a "step change" unless they loose their vacuum.

Had the top of the valve gone milky white?

This series of valves have a little pip to orientate the valve in the holder.

The holder has a wire clip that can knock the pip off.

Cheers

Mike T

[julie_m]

Originally Posted by Boater Sam

Glad it now works but you need to consider replacing the EL41 grid 1 coupling capacitor, its leakage is possibly what killed the original valve.

There isn't one in a P45! It's a "short" superhet, with no gain stage between the detector and the audio output valve.

[Boater Sam]

Sorry, never looked. Still its good advice for next time. I'm getting paranoid about newbies melting transformers. Set protection league member.
It is unusual for EL41s to just pack up.

' Its a valve, the sound valve, simple'

[G8HQP Dave]

EL41 are quite likely to get a bit gassy, then go into thermal runaway and cook themselves.