Author Topic: Sencore MU-150 GM Pot  (Read 799 times)

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Offline Quarlo KlobrigneyTopic starter

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Sencore MU-150 GM Pot
« on: November 30, 2022, 12:18:44 am »
Can anyone help me understand why the GM pot R20 which is a wirewound go open?
]I can show a photo of the break if necessary.
The break is in the 50K not the 5K section.
Ganged together and not a standard of mfg. it's unobtanium.
I can get separate wirewound pots but not ganged.


So the main question being, in the circuit provided in jpg or pdf (page 13) what is the reason for a wirewound pot?

I don't see any current or voltage issues

I await your feedback to help me understand as to why a 2W pot is used.
https://bama.edebris.com/download/sencore/mu150/MU150%20Service%20Manual.pdf

edited for all the  placed in my text. This happens every time I post.
« Last Edit: November 30, 2022, 12:22:31 am by Quarlo Klobrigney »
Voltage does not flow, nor does voltage go.
 

Offline coromonadalix

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Re: Sencore MU-150 GM Pot
« Reply #1 on: November 30, 2022, 01:56:56 am »
maybe an mechanical stress  ???    can you show a picture of the pot ??

Unless the circuit as high voltage passing thru it, a carbon based potentiometer woud fry ??

In the past i did make some fit of dual gang pots, IE: same series body, and switch one of them to fit the needs  in audio stuff

example:  with some pliers / cutters  slowly unbend the case pins, remove one stage and switch it for another value  but having the same body ??

the second image are 2watts dual gang potentiometers, the same trick could be used

EDIT:  oh i remembered,  in the past some of theses pots  since they where wirewounded had a "somekind of a notch feeling" when you passed on the wirewound,  does your's do that

Like a variac transformer, you sense the wirewound as you turn ??
« Last Edit: November 30, 2022, 02:05:27 am by coromonadalix »
 

Offline Quarlo KlobrigneyTopic starter

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Re: Sencore MU-150 GM Pot
« Reply #2 on: November 30, 2022, 02:09:08 am »
It's late.
I did say (I think) that that's how I knew there was damage and I would take a photo, and your photos can't be bought.
Yes I do know how to cobble together pots.

Tomorrow there will be a photo........ :=\ :=\ :=\
Voltage does not flow, nor does voltage go.
 

Offline Quarlo KlobrigneyTopic starter

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Re: Sencore MU-150 GM Pot
« Reply #3 on: November 30, 2022, 02:50:25 pm »

The original pot when actuated would take the meter, a 90° arc, from 0°-30°, then to 0 then to 60°-90°
I already knew the about the strange double pot configuration years ago.


I messed about with another 50K WW pot, but it is smaller in diameter.
I'm going to have to do some mechanical work to bung it in the original back half. Something I don't want to do. AT ALL.


I'll have to get creative with J-B Weld and metal. The worst part is the front shaft is too short. Enter a shaft coupler. I would not want to show what that all put together would look like. :'(


Anyway, getting back to the original question, I still need an opinion why the pot would burn.
The appears to have no discernible current or HV to cause such a thing.
Open for analysis and opinion.

Here are the photos from this morning.
They will show:
1) The original unmarked (manufacturer) naked 50K pot.
2) The full open original.
3) The original pot wiper burn.
4) The original back (5K) half with the possible complexity of the replacement conjoining.
5) The original back (5K) half with the possible complexity of the replacement conjoining.
6) The original back (5K) half with the possible complexity of the replacement conjoining.
« Last Edit: November 30, 2022, 02:52:56 pm by Quarlo Klobrigney »
Voltage does not flow, nor does voltage go.
 

Offline coromonadalix

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Re: Sencore MU-150 GM Pot
« Reply #4 on: November 30, 2022, 03:51:38 pm »
I know it's not fun    but   in the end if it still works okay,   that's your reward    :-+

It is still a good piece of instrument ...
 

Offline Quarlo KlobrigneyTopic starter

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Re: Sencore MU-150 GM Pot
« Reply #5 on: December 02, 2022, 12:31:37 pm »
Bueller?

Doesn't anybody wish to offer a guess as to why a pot would burn up so with such low current - low voltage?
« Last Edit: December 02, 2022, 12:34:35 pm by Quarlo Klobrigney »
Voltage does not flow, nor does voltage go.
 


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