J.A. Michell Prisma restoration

Nibeling06

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May 2, 2022
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Hi AngrySailor,

I have carefully read the story of your restoration: really interesting. Thank you for documenting the entire restoration process, it is very generous of you and instructive.

I have a Prisma too that I am in the process of refurbishing. I have a problem with the 45 rpm pots not working. I wonder how you removed the piece of white plastic. Is it just screwed on?

Thank you !
 

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AngrySailor

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Hi AngrySailor,

I have carefully read the story of your restoration: really interesting. Thank you for documenting the entire restoration process, it is very generous of you and instructive.

I have a Prisma too that I am in the process of refurbishing. I have a problem with the 45 rpm pots not working. I wonder how you removed the piece of white plastic. Is it just screwed on?

Thank you !
I am honest trying to remember how that was assembled. I do know that you are VERY close to having the potentiometer fly apart at that stage... I lost a wiper brush during an “oopsie” right about this stage. For some reason I’m thinking you don’t have to remove that part. I THINK... you need to carefully pry the cover from the rubber surround at this stage if you are trying to access inside the motor block assembly. Then you can test the pot, my pot snapped apart revealing the working at this stage but the brush launched and was never seen again. I whittled one from a pencil graphite ans it’s been working fine however I rarely have to even tweek the speed.
Do you know where the coarse adjustment pot is and how to access it? Would this bring your 45 range into an acceptable window?
 

Nibeling06

New Around These Parts
Joined
May 2, 2022
Messages
2
Thank you for your reply.

The 33 rpm fine tuning pot works well. When I switch to 45 rpm mode, the motor remains stuck at 40 rpm and I have no speed variation when I activate the fine tuning pot, which moreover has no rotational resistance, which leads me to think that there is a problem inside.

Following your advice, I will proceed with caution in the repair of this part.

I know where the coarse adjustment pot is, you explained it very well in a previous post. I still try to solve the problem of this potentiometer, although it is not a crucial issue for me, because I have no 45 rpm record. I just want a fully working turntable !

To be continued...
 

AngrySailor

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Oct 15, 2014
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Tagline
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Thank you for your reply.

The 33 rpm fine tuning pot works well. When I switch to 45 rpm mode, the motor remains stuck at 40 rpm and I have no speed variation when I activate the fine tuning pot, which moreover has no rotational resistance, which leads me to think that there is a problem inside.

Following your advice, I will proceed with caution in the repair of this part.

I know where the coarse adjustment pot is, you explained it very well in a previous post. I still try to solve the problem of this potentiometer, although it is not a crucial issue for me, because I have no 45 rpm record. I just want a fully working turntable !

To be continued...
I believe you must remove the pulley from the motor spindle then carefully pry the “lid” off the motor housing. Mine was only glued with pliable glue at a few places along each side. This will allow you to access the motor housing internals where the potentiometer connections are. If you gently pry on the white plastic around the potentiometer spindle (on top of the motor cover) you should be able to access the workings of the potentiometer, the wiper and such (this is where the wiper goes MIA), but you will need to open the motor housing to access electrical test points/connections of that pot. Good luck, mine was easy to open so don’t shy away from opening the motor “block”, just use a razor and “spudger” and gently separate the glue and pry at it with patience.
 
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