Pye AM/FM Piper P117. - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Nuvistor · 28th Jul 2021, 9:28 pm

Is it possible the hum is coming from the on/off switch or wiring at the back of the volume control?

FERNSEH · 28th Jul 2021, 11:13 pm

Hi Frank,
the mains wiring has been dressed well away from the volume control and the switched mains neutral is returned to the smoothing capacitor ground tag. In many sets it's quite common to find the mains neutral is connected to the volume control earth tag and then by a piece of wire to chassis. Lead lengths can be long enough to develop a few millivolts of AC.

DFWB.

FERNSEH · 29th Jul 2021, 8:22 pm

I've signed off the Pye P117. Can't do much more to improve it.

However, I've bought another AM/FM Piper. Compared with the previous set this one appears to be in better condition.
Check out the fuse. The first item to attend to.

DFWB.

bobhowe · 29th Jul 2021, 8:29 pm

Hi David could be worse seen silver paper out of a cigarette packet wrapped round fuses

FERNSEH · 29th Jul 2021, 8:59 pm

Hi David could be worse seen silver paper out of a cigarette packet wrapped round fuses
Hi Bob,
that was a common sight in the old days of radio and TV servicing.
The original mains cable had been replaced with one with with brown and blue leads. That would be OK except the brown was connected to the chassis and the blue to the fuse.
Before I do anything with this set connect the mains lead correctly and fit a fuse.

DFWB.

bobhowe · 29th Jul 2021, 9:32 pm

Hi David are you going to do a minimum component change kind regards Bob

FERNSEH · 29th Jul 2021, 10:12 pm

Hi Bob,
312volts is present at the anode of the ECL82 pentode section and no volts on the screen grid. The set did for a brief instant come to life and then became silent again. It's possible the "upper" winding on the output transformer is open circuit. The waveband switch bracket has to be removed to gain access to the output transformer and HT resistor R20.
See post No.18 for the circuit diagram.

DFWB.

bobhowe · 29th Jul 2021, 10:53 pm

Hi David the same happened to me on one of my DAC90As had the chassis out of the cabinet changed the grid coupling capacitor tuned into a station worked for a few seconds went dead did a few voltage checks than did a resistance check on the output transformer and the primary side was o/c . Have you got a spare transformer ? kind regards Bob

Boulevardier · 29th Jul 2021, 11:37 pm

Quote:

Originally Posted by bobhowe

Hi David the same happened to me on one of my DAC90As had the chassis out of the cabinet changed the grid coupling capacitor tuned into a station worked for a few seconds went dead did a few voltage checks than did a resistance check on the output transformer and the primary side was o/c . Have you got a spare transformer ? kind regards Bob

What on earth could cause that to happen?

Mike

Leon Crampin · 30th Jul 2021, 10:57 am

I came to the conclusion that there was not much to be done to improve the performance and hum level in this set. Of course, I'm always interested to hear of any improbvements that others may make.

This set is a killer to work on with the exposed fuse clips at mains potential. I cut up a plastic milk carton and made a cover which just clips in. Cut a suitable rectangle to cover the fuses and include 2 locating tabs at 6 and 12 O'clock to engage with the slots in the chassis. The cover can then be just sprung into position and is thin enough to allow the back to be fitted.

Leon.

paulsherwin · 30th Jul 2021, 11:20 am

You do wonder why UK manufacturers made these budget AM/FM second sets at all, especially as all sorts of nasty compromises were involved to keep the price down. All the FM programming was available on AM, and the AM transmitters had much less bandwidth limiting and compression than they do today. The sound quality must have been very similar, especially given the large amounts of top cut applied in the AF stages.

Nuvistor · 30th Jul 2021, 11:42 am

Quote:

Originally Posted by paulsherwin

You do wonder why UK manufacturers made these budget AM/FM second sets at all,

Something new to temp customers, If the customer already owns an AM only set the FM addition is a selling point. Keeping the wholesale price down due to the high Purchase Tax payable at that time would be important.
All conjecture on my part.

bobhowe · 30th Jul 2021, 1:17 pm

Hi Mike possibly green spot or a failing grid coupling capacitor years ago look output transformer failure on this forum kind regards Bob

eddie_ce · 30th Jul 2021, 1:49 pm

Would temporarily supplying the heaters of the ECL82 with DC be a way of determining if the problem is in the valve itself or am I barking up the wrong tree?

Boulevardier · 30th Jul 2021, 1:58 pm

Quote:

Originally Posted by bobhowe

Hi Mike possibly green spot or a failing grid coupling capacitor years ago look output transformer failure on this forum kind regards Bob

Thanks Bob. Just seems weird and cussed that, seconds after relieving any stress on the o/p xformer by replacing "that capacitor", the damned xformer went and failed on you! Can't really see any immediate causal mechanism that would connect the two events in that direction...

Mike

Mike

bobhowe · 30th Jul 2021, 2:13 pm

Hi Mike these sets over 60 years old & some have not been stored in favourable conditions damp sheds lofts etc and the odd set dont like been woken up

it is learning curve for me & i dont take anything for granted kind regards Bob

Sideband · 30th Jul 2021, 2:34 pm

It's very common...the green spot was already there and eaten through the copper winding. When the HT hit the transformer and the UL41 started working, the transformer just couldn't cope.

FERNSEH · 30th Jul 2021, 10:38 pm

The output transformer is OK. The fault turned out to be R20 having gone open circuit. The set is at present working on the medium waveband.
Hum level is low in this set. An early production set, made late 1957.

DFWB.

bobhowe · 31st Jul 2021, 1:15 pm

Hi David glad you have fixed the fault nice to see another set working kind regards Bob

FERNSEH · 31st Jul 2021, 3:22 pm

Hi Bob,
the set is fully working now, good performance on the VHF and medium wavebands. Absolutely hopeless on long waves, but so is the other P117.
R20 replaced by a 1,800 ohm 10 watt resistor. That's not going to fail again.
Measured 55 volts across the resistor so 36mA is passing through it.
P = I^2 . R = 1.95watts.

DFWB.

28th Jul 2021, 9:28 pm	#21
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: Pye AM/FM Piper P117. Is it possible the hum is coming from the on/off switch or wiring at the back of the volume control? __________________ Frank

28th Jul 2021, 11:13 pm	#22
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Pye AM/FM Piper P117. Hi Frank, the mains wiring has been dressed well away from the volume control and the switched mains neutral is returned to the smoothing capacitor ground tag. In many sets it's quite common to find the mains neutral is connected to the volume control earth tag and then by a piece of wire to chassis. Lead lengths can be long enough to develop a few millivolts of AC. DFWB.

29th Jul 2021, 8:22 pm	#23
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Pye AM/FM Piper P117. I've signed off the Pye P117. Can't do much more to improve it. However, I've bought another AM/FM Piper. Compared with the previous set this one appears to be in better condition. Check out the fuse. The first item to attend to. DFWB. Attached Thumbnails

29th Jul 2021, 8:29 pm	#24
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Re: Pye AM/FM Piper P117. Hi David could be worse seen silver paper out of a cigarette packet wrapped round fuses

29th Jul 2021, 8:59 pm	#25
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Pye AM/FM Piper P117. Hi David could be worse seen silver paper out of a cigarette packet wrapped round fuses Hi Bob, that was a common sight in the old days of radio and TV servicing. The original mains cable had been replaced with one with with brown and blue leads. That would be OK except the brown was connected to the chassis and the blue to the fuse. Before I do anything with this set connect the mains lead correctly and fit a fuse. DFWB.

29th Jul 2021, 9:32 pm	#26
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Re: Pye AM/FM Piper P117. Hi David are you going to do a minimum component change kind regards Bob

29th Jul 2021, 10:12 pm	#27
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Pye AM/FM Piper P117. Hi Bob, 312volts is present at the anode of the ECL82 pentode section and no volts on the screen grid. The set did for a brief instant come to life and then became silent again. It's possible the "upper" winding on the output transformer is open circuit. The waveband switch bracket has to be removed to gain access to the output transformer and HT resistor R20. See post No.18 for the circuit diagram. DFWB.

29th Jul 2021, 10:53 pm	#28
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Re: Pye AM/FM Piper P117. Hi David the same happened to me on one of my DAC90As had the chassis out of the cabinet changed the grid coupling capacitor tuned into a station worked for a few seconds went dead did a few voltage checks than did a resistance check on the output transformer and the primary side was o/c . Have you got a spare transformer ? kind regards Bob

30th Jul 2021, 10:57 am	#30
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,870	Re: Pye AM/FM Piper P117. I came to the conclusion that there was not much to be done to improve the performance and hum level in this set. Of course, I'm always interested to hear of any improbvements that others may make. This set is a killer to work on with the exposed fuse clips at mains potential. I cut up a plastic milk carton and made a cover which just clips in. Cut a suitable rectangle to cover the fuses and include 2 locating tabs at 6 and 12 O'clock to engage with the slots in the chassis. The cover can then be just sprung into position and is thin enough to allow the back to be fitted. Leon.

30th Jul 2021, 11:20 am	#31
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,943	Re: Pye AM/FM Piper P117. You do wonder why UK manufacturers made these budget AM/FM second sets at all, especially as all sorts of nasty compromises were involved to keep the price down. All the FM programming was available on AM, and the AM transmitters had much less bandwidth limiting and compression than they do today. The sound quality must have been very similar, especially given the large amounts of top cut applied in the AF stages.

30th Jul 2021, 1:17 pm	#33
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Re: Pye AM/FM Piper P117. Hi Mike possibly green spot or a failing grid coupling capacitor years ago look output transformer failure on this forum kind regards Bob

30th Jul 2021, 1:49 pm	#34
eddie_ce Hexode Join Date: Aug 2010 Location: nr. Hannover, Germany Posts: 372	Re: Pye AM/FM Piper P117. Would temporarily supplying the heaters of the ECL82 with DC be a way of determining if the problem is in the valve itself or am I barking up the wrong tree? __________________ Eddie BVWS Member. Friend of the BVWTM

30th Jul 2021, 2:13 pm	#36
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Re: Pye AM/FM Piper P117. Hi Mike these sets over 60 years old & some have not been stored in favourable conditions damp sheds lofts etc and the odd set dont like been woken up it is learning curve for me & i dont take anything for granted kind regards Bob

30th Jul 2021, 2:34 pm	#37
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,571	Re: Pye AM/FM Piper P117. It's very common...the green spot was already there and eaten through the copper winding. When the HT hit the transformer and the UL41 started working, the transformer just couldn't cope. __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

30th Jul 2021, 10:38 pm	#38
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Pye AM/FM Piper P117. The output transformer is OK. The fault turned out to be R20 having gone open circuit. The set is at present working on the medium waveband. Hum level is low in this set. An early production set, made late 1957. DFWB.

31st Jul 2021, 1:15 pm	#39
bobhowe Heptode Join Date: Jun 2005 Location: Sunderland, Tyne and Wear, UK. Posts: 661	Re: Pye AM/FM Piper P117. Hi David glad you have fixed the fault nice to see another set working kind regards Bob

31st Jul 2021, 3:22 pm	#40
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Pye AM/FM Piper P117. Hi Bob, the set is fully working now, good performance on the VHF and medium wavebands. Absolutely hopeless on long waves, but so is the other P117. R20 replaced by a 1,800 ohm 10 watt resistor. That's not going to fail again. Measured 55 volts across the resistor so 36mA is passing through it. P = I^2 . R = 1.95watts. DFWB. Last edited by FERNSEH; 31st Jul 2021 at 3:27 pm.