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Technics SL D2 speed issue solution

Celt said:
Only the electrolytics. Higher voltage ratings are okay...even desirable....but stick with marked tolerances as close as possible.
Click to expand...

I'll give it a try (Digicon caps - with focus on tolerances).

It is interesting that my turntable will hold speed for about 20 minutes when starting off cold and then speed lock is lost and it runs fast (no pitch control possible). If I shut off the unit and then turn it immediately back on it will lock at speed, but only for a few seconds before losing it. Shut it off and then on again (after stopping the platter) and it will lock to speed, but then drift up.

Is this the behavior of a leaky cap(s)? or a faulty speed control chip (IC AN630U).
I'm pretty confident now it's not the pots or speed switch (very well cleaned and de-oxidized at this point).
 
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Celt said:
IME, that is the common occurrence with leaky caps in a servo circuit.
Click to expand...

I wonder too if could also be the IC chip (AN630U)?

I can reproduce the speed up issue consistently. All tests done at 33 1/3 rpm selected.

1. Turn on the turntable cold and it will run perfectly for about 20 minutes - then lose lock and speeds up.
2. Turn turntable off then on and it will run perfectly for about 10-15 seconds then lose lock and speeds up. I can do this over and over again. It will always run with speed lock at first.
3. Unplug the the turntable while running and it will run perfectly for about 30 seconds and then lose lock and speeds up.
4. "Switch" the speed to neutral (zero) and let the platter stop, power still on, then switch to 33 1/3 rpm and the unit will run perfectly for only 1-2 seconds then lose lock. Only turning unit completely off or unplugging it buys me more time before speed lock is lost.

If I leave the unit un-powered for a few hours, the above steps repeat. I can play one side of one LP one time this way. Not practical of course.

So I do wonder if leaky caps are predictable like this? There does seem to be a temperature effect. The IC chip does have a heat sink over it.
(https://www.vinylengine.com/library/technics/sl-d2.shtml) with link to service manual/schematic).

I more curious than anything in terms of others experience. Has anyone had to replace the IC chip? or bad caps can be temperature sensitive and behave the same way as noted above.
 
I pulled several caps...they tested bad...since there was only an average of six caps on each board...it only made sense to replace all of them.
Why do half of them and have to go back in a year later and replace the rest?
 
I just received a SL-D2 with these symptoms, it will be interesting to see if cleaning the pot and/or replacing the capacitors fixes it.
 
mzeitlin3348 said:
I wonder too if could also be the IC chip (AN630U)?

I can reproduce the speed up issue consistently. All tests done at 33 1/3 rpm selected.

1. Turn on the turntable cold and it will run perfectly for about 20 minutes - then lose lock and speeds up.
2. Turn turntable off then on and it will run perfectly for about 10-15 seconds then lose lock and speeds up. I can do this over and over again. It will always run with speed lock at first.
3. Unplug the the turntable while running and it will run perfectly for about 30 seconds and then lose lock and speeds up.
4. "Switch" the speed to neutral (zero) and let the platter stop, power still on, then switch to 33 1/3 rpm and the unit will run perfectly for only 1-2 seconds then lose lock. Only turning unit completely off or unplugging it buys me more time before speed lock is lost.

If I leave the unit un-powered for a few hours, the above steps repeat. I can play one side of one LP one time this way. Not practical of course.

So I do wonder if leaky caps are predictable like this? There does seem to be a temperature effect. The IC chip does have a heat sink over it.
(https://www.vinylengine.com/library/technics/sl-d2.shtml) with link to service manual/schematic).

I more curious than anything in terms of others experience. Has anyone had to replace the IC chip? or bad caps can be temperature sensitive and behave the same way as noted above.
Click to expand...
I'm dealing with this exact issue and its not the electrolytic caps. Just wasted an hour replacing them for no reason. When I find the real reason I will make a response to this post.
 
It was the AN630U IC in my case, I was able to harvest one from a Technics SL-D5 board luckily. It does appear these are still available from China for around $17 at the time of this post, but Panasonic has long since discontinued them and even the datasheets are sparse.
 
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