Victor TT 101 vs TT 81
According to the specs at Vintageknob, it is Coreless, but with substantially less slots (24 vs 180) TT 101 http://www.thevintageknob.org/jvc-TT-101.html TT 81 http://www.thevintageknob.org/jvc-TT-81.html |
VintageKnob is often an unreliable source. You can download the Service Manuals for both TT-81 and TT-101 units from Vinyl Engine http://www.vinylengine.com/library/jvc/tt-81.shtml http://www.vinylengine.com/library/jvc/tt-101.shtml which disclose that the 101 is coreless but not the 81. They BOTH however, share the bi-directional servo control (a Victor patent) which IMHO is one of the secrets to their exceptional performance. |
I am blown away by the amount of interest in these Victor motors. When they were selling them everyone wanted the Technics, or the Kenwood, or the Micro three arm, etc. One hearing and I knew these were special but stopped using it decades ago probably due to the really bad base and arm arrangement. I have never had to fix mine but I will tell you it does act up if you don't use it. When I took it out to mount in the new base it took almost all day for it to figure out how to run right and that was with me coaxing it along!! I've mechanically worked on it, changed the thrust disc, lubed and polished the shaft, etc. but have not had to do anything electrical to it yet. Someone mentioned Bill Thallman and while I don't know if he has ever worked on a TT-101 he is an electronics wiz-bang and I would trust him with mine. I have guys at the factory and I know a few engineers with the patience for this work but they are not experts on this item. HW |
Dear HWS, Bill Thalmann's shop is about 20 minutes from me, and Bill has worked on my TT101, twice. Bill has also worked (successfully) on several of my other DD turntables and on one of my Beveridge direct-drive amplifiers. But when my TT101 was in Bill's shop (last year), the problem was intermittent, and the unit worked fine, for 2 weeks, on Bill's workbench. We could not make it fail over there. In my house, it was working OK much of the time but would occasionally malfunction in a way I will describe. In search of a cause, we (Bill and I) surmised that there was a bad solder joint somewhere. (This is after Bill had already replaced every electrolytic except one and also re-soldered many of the joints.) At that point, Bill was understandably rather tired of fooling with it. I am a fairly decent DIYer myself, but not with ICs and not so experienced with any sort of solid state gear. However, in my spare time and because I have other tt's to use, I went in there looking for possible bad connections. I suspected that there may be a cracked wire going into one of the many beige-colored multi-prong connectors that connect different PCBs to each other. Two in particular on the board that is tucked up under the top escutcheon, housing the servo mechanisms, seemed loose. So I cut off the beige connectors and hard-soldered those wires to the prongs. (Both are 4-prong connections.) Along the way, I also replaced the one electrolytic that Bill missed doing earlier; it sits alone in that servo board up under the top piece. The result of my labors was to make an intermittent problem into a permanent one! Here is the failure mode: The tt comes up to speed based on the tach reading "33.33", but very shortly thereafter, within less than a minute, you will see readings suggesting the speed is off, 33.32 then 33.34, etc, typically. At that point, the motor shudders significantly and shuts itself down; the platter coasts to a stop with no brake action. The tach goes blank, except for the decimal point. That's the story. This is what it used to do only intermittently. I must say though that I had not detected the motor shudder symptom earlier, but that may have been because the tt was then bolted into a sturdy and heavy plinth. To work on it on my bench, I built a lightweight jig which enables me to flip it upside down easily without risk of damage to the innards. The jig is supported only by 3 metal threaded rods, which is probably why the motor can shake the whole assembly. The bearing is dead silent throughout all this failure mode. There is no rubbing sound or other friction noises. My hypothesis is that the servo is failing in one of the two directions such that the correction mechanisms are fighting each other; that's how I explain the motor shudder prior to shutdown. I have thoughts of taking it back to Bill, now that the problem is sure to occur in his hands. He is a superb guy in all ways. However, I thought perhaps you may have a guy who is steeped in servo technology who might provide some insight. |
