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Old 30th Oct 2019, 9:28 pm   #1
vampyretim
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Default Pye Fenman l vol pot.

Hello,

I'm repairing a Pye Fenman l which has a dodgy vol pot. It goes crackly even after blasting it with switch cleaner. Can anyone recommend a suitable replacement? I know 1M pots aren't too difficult to obtain but I need one that will physically fit.

Any help greatly appreciated.

Many thanks.
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Old 30th Oct 2019, 10:43 pm   #2
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Default Re: Pye Fenman l vol pot.

Here you go. If you look halfway down the page there is a datasheet you can click on to get the dimensions to see if it will fit. You might well have to cut the shaft. https://uk.rs-online.com/web/p/potentiometers/0168128/ Also check any coupling capacitors as if you have significant dc on the pot it won't help things. Cheers, Jerry
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Old 31st Oct 2019, 10:23 am   #3
David G4EBT
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Default Re: Pye Fenman l vol pot.

The volume control is just an unswitched 1 meg pot - the one that Jerry gave the link to from RS would do fine. Modern pots have plastic shaft - your original one has a metal shaft. If you wanted a metal shafted one, Blore Edwards would supply one, but if the shaft on the RS one is long enough (Fenman1 shafts are all long), it would fit fine.

It may be worth mentioning the knobs.

If you've already managed to pull off the crumbly push-on polystyrene knobs without then disintegrating you've done well. If the knobs are still in place, don't try to pull them off from the front as they're very fragile. Much safer - when the chassis is removed with the dial still in place - to gently ease the knobs off from the rear with a screwdriver. You'll never find replacement knobs due to their unique design and fragilty. Despite my best efforts, all of the knobs on a Fenman I I restored some years back were crumbling and I could only save the front 'disc' part of the knobs. I had to turn new shafts in clear Perspex, sleeved with aluminium to stop them fracturing when the grub screw was tightened.

Below is a pic of the underside of the chassis with the (unswitched) volume control and the switched tone control highlighted.

The metal cover of the pot is grounded to the chassis with tinned wire as I recall.

The other pics show the extent to which I had to go to 're-manufacture' the four polystyrene knobs. (In addition to restoring the chassis and cabinet). Restoring the set was a labour of love for a nephew or I wouldn't have bothered. The Fenman1 performs well enough and isn't unattractive, but it was not Pye's finest hour. (I don't know if the Fenma2 - quite a different set - retained the same design of knob. Hopefully not).

Hope that's of interest and help.

Good luck with the restoration.
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Old 31st Oct 2019, 4:43 pm   #4
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Default Re: Pye Fenman l vol pot.

I think the Fenman I, like the Fenman II, has an extra tap on the volume pot for tone control? If this is the case finding a replacement will be almost impossible. It might be worth dismantling, cleaning and lubricating all the moving contacts in the existing pot and hope for the best.

Regards
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Old 31st Oct 2019, 5:07 pm   #5
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Default Re: Pye Fenman l vol pot.

Thanks for the replies. I did unfortunately wreck two of the polystyrene knobs when I pulled them off, they're very fragile, I wasn't heavy handed with them but I was very cross with myself! The replacement knobs that you made look great David.

I will try the R.S pot and if I have any trouble I will try to obtain a metal one. I'm not in the workshop today but if memory serves me well there are only three tags on the pot.

Thanks again,
Tim.
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Old 31st Oct 2019, 5:38 pm   #6
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Default Re: Pye Fenman l vol pot.

If the "Trader" service sheet for the Fenman I is to be believed (1257,) the volume control has a tap...
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Old 1st Nov 2019, 12:19 pm   #7
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Default Re: Pye Fenman l vol pot.

I have often used plastic-shafted pots. to replace metal spindled ones without any problems.
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Old 1st Nov 2019, 1:22 pm   #8
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Default Re: Pye Fenman l vol pot.

He either needs to find one with the special loudness tap or repair the original.
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Old 1st Nov 2019, 1:33 pm   #9
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Default Re: Pye Fenman l vol pot.

Quote:
Originally Posted by Nanozeugma View Post
If the "Trader" service sheet for the Fenman I is to be believed (1257,) the volume control has a tap...
I checked with Blore Edwards some time ago to see if they could do tapped pots and was told no - they'd got rid of the tooling.

I wonder if it would make much difference if a normal log pot was fitted and R31 and C58 (which are connected in series between the tap and ground) were discarded? I doubt it, but the easiest way to find out would be to disconnect the tap on the existing control and see if their is any discernible difference with it out of circuit.

Tapped volume controls seem to have been a bit of a fad in the mid 50s that came and went.
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Old 1st Nov 2019, 2:19 pm   #10
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Default Re: Pye Fenman l vol pot.

It does make a difference, David. I've got one where someone (not me, I hasten to add) in the very distant past has replaced the original pot with a standard one and although the sound is very acceptable, it spoils that classic 'tone' for music at lower and 'normal' volume settings.
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Old 1st Nov 2019, 3:36 pm   #11
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Default Re: Pye Fenman l vol pot.

The "fad" that came and went in the 1950's kept on going with Grundig at least and in a lot of the stuff by various manufactures that I used to service that was made in the 1970's and possibly beyond....

Lawrence.
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Old 1st Nov 2019, 3:55 pm   #12
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Default Re: Pye Fenman l vol pot.

The radio will sound like any other 50s FM woody with a standard pot fitted. The 'loudness' tape takes the set to another level and will make it 'sound' as good as a Grundig 3028 or whatever. Some would say that 'loudness' is a 'colouration', but who cares with a domestic radio! It means that the base control (if fitted) can be left at 'mid' position all the time, without keep having to twiddle it for less bass at higher volume settings.

Just to add - you'll never get that same tone at lower volume settings with this radio if you fit a 'normal' type volume pot.
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Old 1st Nov 2019, 4:03 pm   #13
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Default Re: Pye Fenman l vol pot.

Before you scrap the pot, try taking the cover off it and packing it with Vaseline. It worked for me with a very noisy and apparently irreparable pot on a 1930s HMV.
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Old 1st Nov 2019, 4:07 pm   #14
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Default Re: Pye Fenman l vol pot.

Absolutely!

Even if the pot is still slightly noisy I wouldn't worry about it, just live with it.
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Old 5th Nov 2019, 3:49 pm   #15
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Default Re: Pye Fenman l vol pot.

Quote:
Originally Posted by PaulR View Post
Before you scrap the pot, try taking the cover off it and packing it with Vaseline. It worked for me with a very noisy and apparently irreparable pot on a 1930s HMV.
Wow, worked like a charm!! I never knew of that little trick!!

Thanks to everyone that helped.
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Old 5th Nov 2019, 4:25 pm   #16
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Default Re: Pye Fenman l vol pot.

It is still working in my HMV several years later so it looks like a good fix.
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