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JVC TT-101 Won't Stop

The Stop button on my recently purchased QL-10 doesn't work. It worked at first after the TT warmed up, but then quit completely. I since have replaced all 37 electrolytic caps on 3 boards, but it made no difference. The power voltages are correct. The button itself is fine and shorts pins 6 and 9 of the P8 connector on the main board, but the motor doesn't stop. What could be wrong? Any particular transistor or adjustment? Please help! -Alex
safesphere
lewm
6,770 posts
 
Ummm.... Best-groove, what are you trying to prove? No one would contest the fact that the TT101 is temperamental.  Least of all, me. So, I don't get it.  Unless you're just trying to be funny, which is fine.

It's also a very fine sounding turntable when all is well.
best-groove's avatar
best-groove
236 posts
 
Ummm.... Best-groove, what are you trying to prove?

I do not want to prove anything I'm only slightly worried if my TT-101 will be repaired; I'm not going to want to keep a dry and warm place just for him, but I'm also amused because I will have for the first time a very metereopatic electronic product.
lewm
6,770 posts
 
Just relax and enjoy it, is my advice.  I do believe that once these initial and endogenous issues have been dealt with by someone like JP, probably all will be well.  But I have back-up tt's, just in case.
gary7's avatar
gary7
49 posts
 
Got back with Dave Brown at  modularsynthesis. These are his thoughts.

Dave Brown, Dec 23, 11:52 PM

It’s been a while since I have looked at the schematics and I was looking for something in common between all of those. My gut reaction is a connector. Tin corrodes and becomes intermittent. I’ve also seen failures mostly on the single sided phenolic boards but without plating it would happen on this board also. On a normal PCB with plating, the connector pins are held firmly to the board. Without plating they are only held on by the rear pads since you can’t solder the front pads since the connector covers them. You can never get the connector absolutely tight to the PCB and the leverage of the pins will rock them. The runs fracture right along the connection to the soldering. It would exhibit the kind of behavior you are seeing and is exasperated by temperature differences.

 

What I do for repairs is use epoxy to glue the connector to the topside of the PCB and on the bottom scrape away the solder mask about 3/15” from the pad and jumper the connector pin over to the fresh copper.

 

Typically you can see the connectors move a bit when you rock them.

 

This makes more sense than a random trace crack or a cold solder joint in that there is constant stress on the pins with the cable tension.

 

The connectors going to the front panel PCB makes the most sense. I think there is a front panel PCB. It’s been a while.

 

Dave
gary7's avatar
gary7
49 posts
 
Well, trying to decide what to do with my TT-101, I pulled it out to have another go at the eyelets. I especially paid attention to the ones around the VR646 & VR647 pots that adjust the quick stop. Put it back together and ran for several hours testing the stop button in both 33 & 45. Seems to be fine, for now. It actually is stopping better. Before the platter had some drift after I hit the stop button. Maybe.....for now.   https://www.youtube.com/watch?v=wIhIO7uoPY4
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