J.A. Michell Prisma restoration

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#1
Figured I’d post this in the turntable section... If you’re new to this project, I am working on (I believe) an early Prisma. I bought it from my Uncle and it was working aside from needing a belt and stylus, (possibly the stobe needs work?) however for some reason he removed the lid and replaced the original legs with rubber feet.

I am in the process of having a plastics fabricator make a reproduction cover for me and I plan to fabricate reproduction legs. Attatched are some factory drawings I’ve come across but I wondered if anyone here has a Prisma that they would post some photos of and maybe even some measurements?

I am after the details of the leg mounting arrangement and how the thumb screw leveling is fabricated. Also details of the prop rod and hole location as I plan to machine a replica.

I am away at work so for now I am gathering information and details required to proceed with the lid reproduction but also wondered if someone can identify the tone arm? I know it’s SME, but what model/series? The cartridge is Shure V15 type IV, I have a spare Shure stylus but am told it was dropped and bent :/ so I ordered a new replacement from Jico. Did I make a mistake there or are their products reasonable quality?

Thanks guys!
 

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#4
Somewhere I have the original box and manual for it. I THINK it’s a 3009 series 3? I wish it was March and I was home to actually get my hands into these projects. It’s surprising what you can get done from away though also. Friends and family have shipped or dropped stuff off where it needs to go, parts ordered online. When I get home everything should be there waiting for me to do my part.

As far as the legs I’m guessing that if you were to pick up the turntable the front legs would be loose? They pivot on the bend inside that channel mounted to the base to cause the leveling effect?

Oh, speaking of getting things done from away, sometimes my Father needs a little motivation to jump into a project or he will “do it later”... He complained his turntable quit “a while ago”, (which turned out to be almost a year ago) while we were organizing shipping for the prisma parts. I ordered him a stylus, belt, alignment tools and a stylus force gauge, then badgered him to read up about cartridge alignment. He messaged me this afternoon, alignment went well and he said it sounds like when he bought it new now!
 

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Gepetto

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#6
Somewhere I have the original box and manual for it. I THINK it’s a 3009 series 3? I wish it was March and I was home to actually get my hands into these projects. It’s surprising what you can get done from away though also. Friends and family have shipped or dropped stuff off where it needs to go, parts ordered online. When I get home everything should be there waiting for me to do my part.

As far as the legs I’m guessing that if you were to pick up the turntable the front legs would be loose? They pivot on the bend inside that channel mounted to the base to cause the leveling effect?

Oh, speaking of getting things done from away, sometimes my Father needs a little motivation to jump into a project or he will “do it later”... He complained his turntable quit “a while ago”, (which turned out to be almost a year ago) while we were organizing shipping for the prisma parts. I ordered him a stylus, belt, alignment tools and a stylus force gauge, then badgered him to read up about cartridge alignment. He messaged me this afternoon, alignment went well and he said it sounds like when he bought it new now!
That tonearm looks like the starship enterprise...
 
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#7
I wonder if the prisma is actually made of “transparent aluminum” and if a dilithium tipped stylus is available!
 

mlucitt

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#8
Someday I would like to get a decent old school manual turntable. Thinking about a Kenwood KD-500 or similar. Direct drive is better for me, no belts or idler arms to worry about. Auto-return is nice in case I fall asleep listening to jazz.
 

laatsch55

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#10
Someday I would like to get a decent old school manual turntable. Thinking about a Kenwood KD-500 or similar. Direct drive is better for me, no belts or idler arms to worry about. Auto-return is nice in case I fall asleep listening to jazz.

How about a Denon DP 1500 with an Infiinity Black Widow tonearm?
 

mlucitt

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#11
How about a Denon DP 1500 with an Infiinity Black Widow tonearm?
Is that the one that looks like a flying saucer? That would be cool. My understanding is that the DP-1000 was designed as an "a la carte" unit to roll your own drive, plinth, cover, arm, cartridge, etc.
 
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#14
Yep, that’s it. It seemed there were a couple variants of this arm also so still not sure exactly what I have. I think there was improved and non-improved models from what I’ve found online, but haven’t found much about the differences. I think I know where the manual might be so I’ll have to ask the Gf to look and snap a pic.

I was able to get on an actual computer instead of my phone for a bit so was able to see some pics better. For the front legs,
It looks like the channel that bolts to the base has stamped bumps for the legs to pivot on. Shouldn’t be to difficult to reproduce, my friend has sheetmetal break, press break and shear at his shop. I got some practice making things shine a while back. Fabricated a set of zoomies for a big block Chevy out of stainless. Took 8-10 hrs per tube to polish plus the flanges and tie bars. Started with 120 grit and worked up to 1200 wet then compound...That was a couple years ago so I guess I’m over my hatred of polishing enough to tackle this job now...
 

mlucitt

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#18
The Denon is way too nice for a guy like me. I might build a platter from an old bicycle wheel and power it up with a washing machine motor running at 2.22 Volts (1800 rpm divided by 33 1/3 divided by 120 VAC), with a grade school ruler for a tonearm and a bent pin for a needle. With this unit need a stereo A/D converter?
 
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#19
Had a friend back home box up my Rotel RA 1412 and PL 2000 for shipping. The Rotel was working as a pre amp in the shop when the tuner attached to it decided to short 110vac to the chassis through the accessory outlet and toasted it. The PL I’ve never used but think it has loose solder traces. Going to have them both repaired and probably put them in the house. I do like the RA as a pre amp for the shop but it really belongs with the other vintage gear.

A friend of mine cut down a big maple tree last year and milled it. He has lots left and is going to help me build a nice stand for my living room for all the gear and some storage space for records and accessories. My ex didn’t want this “junk” in the living room. Traded her in years ago and the new model loves the idea :cool:

The RT 707 pic is stolen from the internet, mine is at the repair guys all tuned up.
 

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