Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

[Radio Scotland]

As above. Doesn't need to be an original part as long as it fits, Also willing to consider just the volume pot without the on/off switch. 250K

See pics for dimensions.


Cheers
Jay

[David G4EBT]

It's a 250K log pot

You'll get a suitable replacement for Bowood Electronics.

Nearest preferred value is 220K with double pole switch, which will be fine:

https://www.bowood-electronics.co.uk...-log-switched/

Bowood seem to be about the only outfit apart from Blore Edwards who supply a good range of switched and unswitched pots, both linear and log, including 470K and 1 Meg, which are often called for.

Hope that helps.

[Radio Scotland]

Originally Posted by David G4EBT

It's a 250K log pot

You'll get a suitable replacement for Bowood Electronics.

Nearest preferred value is 220K with double pole switch, which will be fine:

https://www.bowood-electronics.co.uk...-log-switched/

Bowood seem to be about the only outfit apart from Blore Edwards who supply a good range of switched and unswitched pots, both linear and log, including 470K and 1 Meg, which are often called for.

Hope that helps.

Cheers for that, For some reason i forgot to include the value,



Jay

[Radio Scotland]

Anybody know the power rating of the original pot ?

[Simon Gittins]

I've never seen a power rating for a volume control, they are not supposed to dissipate any significant power.

There are some ideas for repairing the original half way down this article:
http://www.geofex.com/article_folder...s/potscret.htm

[Radio Scotland]

Originally Posted by Simon Gittins

I've never seen a power rating for a volume control, they are not supposed to dissipate any significant power.

There are some ideas for repairing the original half way down this article:
http://www.geofex.com/article_folder...s/potscret.htm

Cheers, But i think the original is knackered, Its been washed in switch cleaner, But no joy. The way it works seems to puzzle me, It's got a centre notch like a balance control. When in the centre notch position the resistance is zero between the two outer pins which causes a short and blows the fuse. Far as i know the resistance between the two outer pins should be constant,

First half of the wiper is around 660k and can be varied, Second half is constant,

Obviously not the original as that should be 250k


Jay

[Sideband]

Originally Posted by Radio Scotland

Anybody know the power rating of the original pot ?

It only has a signal voltage across it. There is isn't a power rating for an ordinary volume control.

It's true that some pots do have a rating but these are usually heavy-duty wirewound types and passing a lot more than just a few hundred microvolts from a detector.

[Radio Scotland]

Originally Posted by Sideband

It only has a signal voltage across it. There is isn't a power rating for an ordinary volume control.

It's true that some pots do have a rating but these are usually heavy-duty wirewound types and passing a lot more than just a few hundred microvolts from a detector.

Just seems like a heavy duty pot, So was wondering if it had a specific power rating,

[Simon Gittins]

The Bowood one in Post 2 should be fine.

The way it works seems to puzzle me, It's got a centre notch like a balance control. When in the centre notch position the resistance is zero between the two outer pins which causes a short and blows the fuse. Far as i know the resistance between the two outer pins should be constant,

That puzzles me as well! There shouldn't be a centre notch and the resistance between the two outer pins should be constant; I can't see how that would cause the fuse to blow though. Perhaps the mechanism of the original is faulty in such a way that the mains switch shorts to the case at the centre of the travel.

[Radio Scotland]

Originally Posted by Simon Gittins

The Bowood one in Post 2 should be fine.

That puzzles me as well! There shouldn't be a centre notch and the resistance between the two outer pins should be constant; I can't see how that would cause the fuse to blow though. Perhaps the mechanism of the original is faulty in such a way that the mains switch shorts to the case at the centre of the travel.

It's a strange one simon, Theres no connection between the case and the switch, Must be L11 That is being shunted to ground when the pot drops to zero ohms, I saw it spark yesterday whilst i was adjusting the volume just before the fuse popped

[Station X]

As far as I can see there shouldn't be any significant voltage on L11 and I don't think shorting it to ground would blow the mains?? fuse.

[Radio Scotland]

Originally Posted by Station X

As far as I can see there shouldn't be any significant voltage on L11 and I don't think shorting it to ground would blow the mains?? fuse.

I agree station X

It's weird.

[Station X]

Might be worth checking the voltage on L11.

[Radio Scotland]

Part no longer needed, See here for an explanation for the issue.

https://www.vintage-radio.net/forum/...83#post1430583

This Thread can be closed now.


Cheers..