Pye P114BQ jewel case radio - UK Vintage Radio Repair and Restoration Discussion Forum

Stylo N M · 18th Dec 2016, 6:46 pm

Hi

I haven't got the radio yet, and I can't work on it just yet, but a friend of mine says it has developed a strange fault, which he has played to me down the phone. The only way I can describe it is like a blowing noise, that is quite loud just like someone letting go of the end of an inflated balloon, and sometimes a squealing sound or a squawk.

I did restore the radio four months ago. The usual parts replaced as per normal, all waxies, a few out of spec resistors, and a new 4 ohm speaker because the old one was water damaged. No water damage was detected in the rest of the set.

The stations I think can just be heard in the background, the radio has worked fine until now since being restored. Any ideas just to get me thinking about it would help. I have a circuit diagram. (it sounds extremely unstable)
Thanks, Paul.

ronbryan · 18th Dec 2016, 7:51 pm

Paul

C24 (Trader sheet), the 8uF HT decoupler would be the first thing to check.

As the battery ages, the internal impedance rises and oscillation becomes more likely.

Ron

Stylo N M · 18th Dec 2016, 9:24 pm

Hi Ron,

yes thank you, i was wondering if that might be a good place to begin.

Paul.

Phil G4SPZ · 19th Dec 2016, 9:11 am

I have had a few cases of severe microphony in DK9x frequency changer valves. Vibration from the 'speaker sets up oscillation at audio frequencies. Try tapping the DK9x gently to see if it provokes or stops the fault.

Stylo N M · 19th Dec 2016, 12:09 pm

Thanks Phil, that's a good idea too. I think I might get it in my mits later today, or tomorow and then I can report back.

Thanks, Paul.

Chindit · 20th Dec 2016, 12:34 pm

Yep. A small elastic band placed snugly around the middle of the valve envelope should cure any microphony. Colin.

MALC SCOTT · 20th Dec 2016, 1:01 pm

Dirty valve bases cause many problems with these and many other battery sets, Malc.

Stylo N M · 22nd Dec 2016, 7:22 am

Hi,

i finaly managed to get hold of the radio late last night, and can conclude that it was indeed the 8uf HT capacitor, which was more or less open circuit, measuring a mere 1.6nf on the component analyser.

The radio is now back in full working order.
Thank you, paul.

18th Dec 2016, 6:46 pm	#1
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Pye P114BQ jewel case radio Hi I haven't got the radio yet, and I can't work on it just yet, but a friend of mine says it has developed a strange fault, which he has played to me down the phone. The only way I can describe it is like a blowing noise, that is quite loud just like someone letting go of the end of an inflated balloon, and sometimes a squealing sound or a squawk. I did restore the radio four months ago. The usual parts replaced as per normal, all waxies, a few out of spec resistors, and a new 4 ohm speaker because the old one was water damaged. No water damage was detected in the rest of the set. The stations I think can just be heard in the background, the radio has worked fine until now since being restored. Any ideas just to get me thinking about it would help. I have a circuit diagram. (it sounds extremely unstable) Thanks, Paul.

18th Dec 2016, 7:51 pm	#2
ronbryan Octode Join Date: Jan 2003 Location: Guildford, Surrey, UK. Posts: 1,960	Re: Pye P114BQ jewel case radio Paul C24 (Trader sheet), the 8uF HT decoupler would be the first thing to check. As the battery ages, the internal impedance rises and oscillation becomes more likely. Ron

18th Dec 2016, 9:24 pm	#3
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Re: Pye P114BQ jewel case radio Hi Ron, yes thank you, i was wondering if that might be a good place to begin. Paul.

19th Dec 2016, 9:11 am	#4
Phil G4SPZ Dekatron Join Date: Apr 2005 Location: Bewdley, Worcestershire, UK. Posts: 4,748	Re: Pye P114BQ jewel case radio I have had a few cases of severe microphony in DK9x frequency changer valves. Vibration from the 'speaker sets up oscillation at audio frequencies. Try tapping the DK9x gently to see if it provokes or stops the fault. __________________ Phil Optimist [n]: One who is not in possession of the full facts

19th Dec 2016, 12:09 pm	#5
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Re: Pye P114BQ jewel case radio Thanks Phil, that's a good idea too. I think I might get it in my mits later today, or tomorow and then I can report back. Thanks, Paul.

20th Dec 2016, 12:34 pm	#6
Chindit Tetrode Join Date: Feb 2011 Location: Bishop Auckland, County Durham, UK. Posts: 97	Re: Pye P114BQ jewel case radio Yep. A small elastic band placed snugly around the middle of the valve envelope should cure any microphony. Colin.

20th Dec 2016, 1:01 pm	#7
MALC SCOTT Octode Join Date: Aug 2006 Location: Willington, County Durham, UK. Posts: 1,499	Re: Pye P114BQ jewel case radio Dirty valve bases cause many problems with these and many other battery sets, Malc. __________________ Malc Scott

22nd Dec 2016, 7:22 am	#8
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Re: Pye P114BQ jewel case radio Hi, i finaly managed to get hold of the radio late last night, and can conclude that it was indeed the 8uf HT capacitor, which was more or less open circuit, measuring a mere 1.6nf on the component analyser. The radio is now back in full working order. Thank you, paul.