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Motor repair for Goldmund Studio TT /w Pabst motor

Well, either I am seriously forum challenged (a possibility) or for the second time my thread on this subject has been removed and is not in the archives. I thought they archived everything, but I guess not. Moderator, could you please stop deleting this. Every time you do I lose all the posts from forum members.

I sent my motor to an electronics firm in California recommended by a friend in the industry. They took one look at it and wouldn't touch it because it had electronics in it and, I guess, they don't do that stuff.

The good news seems to be that the motor windings are very likely ok and the problem actually seems to be related to the internal electronics parts.

Since I saw smoke come out of the motor during my initial investigation of the problem, I had thought the windings were compromised. Removing the bottom cover of the motor reveals a circular circuit board but also visible through a gap where the wires enter the motor are some additional electronics parts. So, when the motor was returned to me I set about disassembling the damn thing myself. In addition to removing the bottom cover, this required removing a couple of C clips and other various bits.

I was expecting to see some heat damage but everything looks fine. There are a lot of Caps, Resistors, Transistors and other three terminal devices in this thing. I am leaning toward the theory that one or more of these transistors have failed and I will be testing them to see if I can locate the problem.

Word on the street has been that Pabst of Germany went out of business in the early '80s. However, in the latest issue of TAS I noted that the review of the Raven AC 3 TT mentioned that it uses a Pabst motor.
willster

Showing 5 responses by willster

willster OP
66 posts
 
Dweller...It would probably seem the way to go to someone not familiar with this table but is obvious to anyone who has examined it closely. The way the platter and motor are configured precludes the use of an off the shelf generic replacement. I still haven't run across any info regarding switching to the JVC motor used in later versions but had the impression that there was some incompatibility difficult to deal with.

Not sure if that's what you meant but your museum curator comment leads me to believe that there is an opinion you are not expressing here. Don't know what your disposable income is like but I simply don't have the cash to replace this turntable with anything comparable. I have been told that when this table was first put on the market, it was the most expensive turntable in the world. Twenty five years ago it cost $13000. Don't know what that would be in today's dollars but I couldn't afford it in even in 1980 dollars.

Thanks for the link references, everyone. I think I've already seen some of this info but I'll definitely check it to make sure
willster OP
66 posts
 
Dweller...perhaps you missed my mention of the Raven AC in the original post.
willster OP
66 posts
 
I decided to call a local repair person recommended to me by a friend. I was then astounded when, with only the knowledge that it was a DC direct drive motor this fellow literally described the internals to me over the phone. He then listed all the most common problems associated with this motor type. He'd never heard of Goldmund or Pabst.

I was impressed enough with his obvious experience that I decided to take a chance and take the motor to him. After seeing it, he suggested a couple of other possible problems to investigate as well.

This guy is one of a kind and a dying breed. His shop was full of mostly midfi gear; Pioneer, Technics, etc. His only real experience with better brands was McIntosh, Marantz and the like. He continued to amaze me with his knowledge of electronics, not to impress anyone, but just in his normal conversation about repair possibilities.

He told me to call him in a week if I hadn't heard from him. So, I'm very encouraged that he can get my motor rolling again. I'll post again with the results.
willster OP
66 posts
 
Bad news. The guy that I put so much faith in doesn't want to spend any more time with my motor, even though he never completely isolated the problem. He has a back log of work and thinks he could repair three of his typical jobs for the time it would take him with my motor. It's a complete cop out. I still think he could probably help me get it going again but he isn't willing. We never even discussed a fee for the work. I would have been willing to pay him for his time. I have few alternatives. The last time I talked to him he told me all the things he thinks I should do to find and repair the problem. I went to him because he is better equipped and prepared for such work. Overall, very disappointing. I've set the motor aside for the moment. Maybe when I'm not so annoyed I'll start in on it again.
willster OP
66 posts
 
Thanks for the info. I ran across this discussion of using a Dual motor quite some time ago and am not quite ready to butcher my turntable in order to make the Dual motor fit, although it might come to that.

I can send pictures to anyone who wants them, but I don't have a website where I can post information.

At this point, I think my motor is fixable. I just put too much faith in the wrong guy. I may end up doing the work myself since no one else has proved reliable. There appears to be a dead short somewhere and I don't think the motor windings are damaged. My current top suspect is a voltage regulator. So, if I can sort out where the fault is, I should be able to affect repairs. I have a good understanding of electronics, but I don't have any experience troubleshooting.

Each failed attempt at finding repair help has at least revealed additional info about the motor and it's condition. Hopefully, at some point the accumulated insights will reach critical mass and I'll get results, either by doing it myself or by finding appropriate help.

Thanks to all who have taken an interest. I do appreciate it.
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