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Old 6th Dec 2021, 12:24 pm   #1
Radio Scotland
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Default Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

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
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Last edited by Radio Scotland; 6th Dec 2021 at 12:49 pm. Reason: Additional info
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Old 6th Dec 2021, 12:46 pm   #2
David G4EBT
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

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.
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Old 6th Dec 2021, 12:51 pm   #3
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

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Originally Posted by David G4EBT View Post
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
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Old 6th Dec 2021, 6:54 pm   #4
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

Anybody know the power rating of the original pot ?
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Old 6th Dec 2021, 9:58 pm   #5
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

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
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Old 6th Dec 2021, 10:11 pm   #6
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

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Originally Posted by Simon Gittins View Post
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
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Old 6th Dec 2021, 10:15 pm   #7
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

Quote:
Originally Posted by Radio Scotland View Post
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.
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Old 6th Dec 2021, 10:18 pm   #8
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

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Originally Posted by Sideband View Post
Quote:
Originally Posted by Radio Scotland View Post
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.

Just seems like a heavy duty pot, So was wondering if it had a specific power rating,
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Old 7th Dec 2021, 9:28 am   #9
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

The Bowood one in Post 2 should be fine.

Quote:
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.
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Old 7th Dec 2021, 11:59 am   #10
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

Quote:
Originally Posted by Simon Gittins View Post
The Bowood one in Post 2 should be fine.

Quote:
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.
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
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Old 7th Dec 2021, 12:18 pm   #11
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

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.
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Old 7th Dec 2021, 12:20 pm   #12
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

Quote:
Originally Posted by Station X View Post
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.
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Old 7th Dec 2021, 12:28 pm   #13
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

Might be worth checking the voltage on L11.
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Old 7th Dec 2021, 3:52 pm   #14
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Default Re: Pilot Little Maestro AC/DC 1939 Volume pot / On off switch

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..
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