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Vintage DD turntables. Are we living dangerously?

I have just acquired a 32 year old JVC/Victor TT-101 DD turntable after having its lesser brother, the TT-81 for the last year.
TT-101
This is one of the great DD designs made at a time when the giant Japanese electronics companies like Technics, Denon, JVC/Victor and Pioneer could pour millions of dollars into 'flagship' models to 'enhance' their lower range models which often sold in the millions.
Because of their complexity however.......if they malfunction.....parts are 'unobtanium'....and they often cannot be repaired.
128x128halcro
pbnaudio's avatar
pbnaudio
1,613 posts
 
Lewm, 


What does the "Krebs mod" consist of ?

Thanks in advance


Peter
lewm
13,043 posts
 
No one really knows.  There's the rub.  The idea is to stabilize the stator (in the Mk2 and Mk3) so as to lessen the effect on the stator of torque inputs prompted by the servo sensing a speed inaccuracy.  The thesis is that very minor displacements of the stator due to torque input lead to spurious or unnecessary further speed corrections, which results in the colorations that some hear with the big Technics DD turntables. You want all the energy to go into the rotor (which essentially IS the platter). Newton's Third Law of motion says that there must be an equal and opposite force (torque) on the stator; the attempt is to cancel the effect of that force.  How this is achieved is a proprietary secret, apparently. Before I re-assembled my Mk3, after getting it back from Bill Thalmann who did the Krebs mod on it, I could easily see that "something" had been done to the structure around the stator, but nothing was obvious about it. Richard Krebs tells me privately that he experimented extensively before arriving at his solution, even ruined a Mk3 in the process, I think he said. I'm sure he's here somewhere.
richardkrebs
422 posts
 

Peter and Lew.

Thanks for your interest in my upgrade. It's not really appropriate for me to promote it via this forum. Anyone interested can PM me directly or go to my krebsupgrade web site.

That said, just a small clarification; during the development phase, I didn't actually ruin my MK3, I ruined its performance, necessitating a reversal of the structural change I had just made. This was a real PITA, taking me months to restore it to the previous iteration. I learnt the hard way that theory and practice and two completely different things.

Also there is a run in aspect and an elapsed time aspect. Full performance isn't realised until around 4 months.


cheers.

lewm
13,043 posts
 
I shouldn't have written that "no one really knows" the nature of the Krebs mod.  Obviously, Richard and Bill do know.  But they ain't talkin'.

My experience agrees with what Richard wrote about "run in".  As I wrote earlier, the differences were at first subtle and now obvious-er and obvious-er.
jb0194
476 posts
 
I will listen for improvements as I run in the Krebs mods, lewm. I will post my impressions in a month or so. One of the things one gets with the Krebs mod is, in essence, a servicing of a 30+ year-old motor. Additionally, the worn bearing thrust plate is replaced. I had caps replaced by Dave Cawley when I purchased my table from a UK seller 5 years ago, and Bill has now replaced those that Dave didn't. So I have serviced pretty much what can be, and I consider this essential maintenance for the table. Add in a fresh gloss black automotive painting of the deck to match a new plinth, and I have the table looking as good as it plays.
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