Another Michell Prisma Restoration....

lsfarzo

New Around These Parts
Joined
Mar 20, 2021
Messages
1
#1
HI all,
after reading AngrySailor's thread about his restoration I finally made up my mind to restore my Pris

I bought it used about 25 years ago and I have left it unused since 2005. A mark in the center of the back leg writes “23 May 1977”.
I would revamp its look and put it again to operations in my stereo chain aside my current turntable.

Here it is at the beginning of the work.
Before first clean.jpg




Here follows the my plan:

1) Turntable legs.
Chrome plating ruined.
This turntable has been stored in a cardboard box for a long time. A flood (few centimeters of water) has happened but none noticed this for some months.
So, now the legs have partly lost their chrome plating and many small black points appeared on them. I think this is due to rust.
After having brought them to a blacksmith they are planned to be brought back to their original shine.
This is pretty simple, indeed.
legs.jpg

black points on legs - rust.jpg


2) 5 Golden-like weights on the platter.
They have lost their original gilding and now are opaque.
Apart from the age of the turntable, this may be due to a wrong action done many years ago, trying to polish them with a wrong and aggressive chemical product.
Here I need your help, please: do somebody knows how to recover them ? A galvanic treatment would do the job??
Could I do something by myself using some special product pr solution or whatever else I could use to make them return to their original shine before going to a blacksmith / company who makes galvanic treatment to restore their gold finish ?
Which is their material?
Below the current situation.
platter and weights small.jpg

weight small.jpg

3) Cover
There are some marks and lids on it, especially on the center part. See below.
20210314_081018.jpg

20210314_081612.jpg

How to remove them safely ?

4) Motor
The turntable motor looks in good conditions and the belt is still in quite good working condition. So I checked it now for rotation stability: even for long term rotation it seems to work pretty well (few adjustment every half an hour) both at 45 and 33 rpm.
Anyway, I remember there were some sudden blips (rotation slowing down) when it was in operations. Since now the TT is w/out arm I can't re-check this now, and will check this later.
Maybe the bearings need to be oiled. When working I can hear a periodic little "tlac tlac" inside the motor which is maybe due to oil drying after so many years.
How to oil the bearing ? Which are the screw to unscrew and how to open the two shell of the inside part? Where to drop the oil drops ?
motor complete small.jpg

backshell small.jpg

upper shell small.jpg



Any help is very well welcomed !

Thanks
Luca
 

George S.

Chief Journeyman
Joined
Feb 18, 2020
Messages
615
#3
That noise is a sure sign the motor needs oiled. Never seen one of those turntables before, so can't help you further. I do know to use the oil sparingly where the exposed shaft enters the motor, have it set so gravity pulls it into the motor. Probably has a bronze bushing there rather than a bearing. Oil it and let it run awhile to work the oil in. Should clear up and run smooth.
Oh, and welcome. I'm sure Andrew the Angry Sailor can help you with this. Pretty sure he has one of those.
 
Last edited:

AngrySailor

Veteran and General Yakker
Joined
Oct 15, 2014
Messages
1,576
Tagline
---not quite right
#4
HI all,
after reading AngrySailor's thread about his restoration I finally made up my mind to restore my Pris

I bought it used about 25 years ago and I have left it unused since 2005. A mark in the center of the back leg writes “23 May 1977”.
I would revamp its look and put it again to operations in my stereo chain aside my current turntable.

Here it is at the beginning of the work.
View attachment 50158




Here follows the my plan:

1) Turntable legs.
Chrome plating ruined.
This turntable has been stored in a cardboard box for a long time. A flood (few centimeters of water) has happened but none noticed this for some months.
So, now the legs have partly lost their chrome plating and many small black points appeared on them. I think this is due to rust.
After having brought them to a blacksmith they are planned to be brought back to their original shine.
This is pretty simple, indeed.
View attachment 50152

View attachment 50153


2) 5 Golden-like weights on the platter.
They have lost their original gilding and now are opaque.
Apart from the age of the turntable, this may be due to a wrong action done many years ago, trying to polish them with a wrong and aggressive chemical product.
Here I need your help, please: do somebody knows how to recover them ? A galvanic treatment would do the job??
Could I do something by myself using some special product pr solution or whatever else I could use to make them return to their original shine before going to a blacksmith / company who makes galvanic treatment to restore their gold finish ?
Which is their material?
Below the current situation.
View attachment 50151

View attachment 50154

3) Cover
There are some marks and lids on it, especially on the center part. See below.
View attachment 50149

View attachment 50150

How to remove them safely ?

4) Motor
The turntable motor looks in good conditions and the belt is still in quite good working condition. So I checked it now for rotation stability: even for long term rotation it seems to work pretty well (few adjustment every half an hour) both at 45 and 33 rpm.
Anyway, I remember there were some sudden blips (rotation slowing down) when it was in operations. Since now the TT is w/out arm I can't re-check this now, and will check this later.
Maybe the bearings need to be oiled. When working I can hear a periodic little "tlac tlac" inside the motor which is maybe due to oil drying after so many years.
How to oil the bearing ? Which are the screw to unscrew and how to open the two shell of the inside part? Where to drop the oil drops ?
View attachment 50155

View attachment 50156

View attachment 50157



Any help is very well welcomed !

Thanks
Luca
Hello Luca! Glad you posted a thread and sorry I missed it till now. Lemme read the rest, you’ll get all the help available here no doubt and welcome.
 

AngrySailor

Veteran and General Yakker
Joined
Oct 15, 2014
Messages
1,576
Tagline
---not quite right
#5
You need to remove the pulley from the motor shaft, then VERY CAREFULLY drill those four rivets holding the motor shell together. The PCB contains the motor windings so be very careful as there are rotors above and below the PCB/windings. See the pics in my thread. Deburr the shaft where the belt pulley was, carefully pull up the top clam shell who’ll gently pushing down on the shaft. Once you have the top shell off, place some masking tape over the windings on the PCB, then do the same to remove the bottom clam shell. Now you can clean and oil the motor bearings. Reassemble with (if I recall) 4-40 nuts and bolts. Do you see that potentiometer on the PCB? That is the course speed adjustment, set you’re 33/45 pots in the middle and set the course as close as you can get to 33 1/3. You should be able to use the built in strobe, if it doesn’t work, print off a strobe disc.

for your cover, wet sand it starting at 1000-1200 grit, work the marks out, sand progressively up to 3000 grit then use a fine acrylic polish to really make it shine. Use the polish on the whole turntable should bring it up also. Don’t sand in one place. This takes time work over large areas and gradually finer grit so you don’t see waves and deep sanding troughs.

Andrew
 

AngrySailor

Veteran and General Yakker
Joined
Oct 15, 2014
Messages
1,576
Tagline
---not quite right
#6
The platter weights are 24k gold plated. Try some fine polish.

min you picture of the bottom of the motor, see that axial screw with the red ink on it? It MAY be possible to remove that and put a drop of oil in. Mine WOULD NOT BUDGE and if it did would need to be set back exactly where it was. This option also does not allow cleaning of the old oil, which is why I disassembled the motor cases. No worries, if you’re gentle.

belts are available from Michell or other TT suppliers, they’re about $30 if I recall.

what is your plan for a tone arm, cart and stylus?
 
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