Potentiometer repair?

[sparkey58]

I have a Pye black box amp for repair, the tone control is a 1k switched pot with a long shaft..it measures 12k the problem is the sort of fibrous material that connects the lug to the track [track is o.k at 1k and the wiper is ok...i touched it and it promptly split..question is where can i get a replacement or a repair method? thanks ,bob

[G6Tanuki]

As a get-you-going kludge - assuming the control is simply wired in series with a tone-correction capacitor on the output-stage [whose insulation really needs to be checked... that burned pot looks like it's been passing some significant current] - swap the two outer-ends of the pot wiring and accept that the tone-control will then work backwards.

I did this sort of kludgery loads of times for elderly people with equally-elderly tellies whose horizontal/vertical-hold/brightness-contrast controls had suffered wear at one end of the track and who were not prepared to pay for an entire new potentiometer-block.

[cathoderay57]

Hi Bob, the lowest resistance new switched pot I could find at rs components was 10k see here https://uk.rs-online.com/mobile/p/po...eters/0168392/ As a tone control I wouldn't have thought the value is too critical? You might need a shaft extender if this item isn't long enough. Cheers, Jerry

[BRASSBITS]

Bowood list a 1k dpst log pot

[sparkey58]

hi thanks for replies i can find plenty of 50mm shaft length unswitched, or 25mm shaft switched...years ago you could buy a coupler for extending the shaft...i can see kits online, but not just the coupler in the UK...i also will have a go with silver conductive paint see if i can repair it..anyone been successful using this?

[cathoderay57]

Here's the coupler - nice and cheap shipped from China but should do the job! https://www.banggood.com/6mm-Shaft-C...r_warehouse=CN cheers, Jerry

[winston_1]

Most pots on British equipment have 1/4" shafts not 6mm, but I guess you could drill that coupler out.

[sparkey58]

thanks for the tip gerry...ordered a few, bob

[John10b]

I’m Lucky to have a friend who can turn out almost anything small, he made a few couplers for me so I could connect two TripleTone Amplifiers together to use in a stereo setup.
Cheers
John

[Ed_Dinning]

Hi Gents, there seems to be a lot of problems with the pots used in black boxes, both types these days.
The EL42 types can be up to 10K, but you need to shunt the pot with a suitable resistor to bring it back down near 1k.

The PCL83 types have a complex feedback circuit and the pots often develop spots where the amp starts to oscillate. These can be expensive to source and not easily found.

Ed

[sparkey58]

taking the pot apart.. the track is still 1k its the connection from end of track to the lug thats gone high [5k] going to try conductive paint over it...but new pot on order just in case!