Tecnics SL-D3 speed problem

mrwood

mrwood

Member
Clean the pots? Oh yes. De-oxit like mad, spinning the wheel like a hamster, sopping it up with Q-tips. Did the same on the speed trim control under the platter access panel.

Speed is stable, perfect, maybe for one side - then at random intervals goes off speed, faster, just as if I had turned the wheel all the way to raise the pitch. If I cut power momentarily and turn the table back on, the speed is rock stable again... for a while. Does this symptom point to some solution?
 
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Check for cracked solder joints around the motor board. If they are broken the system can't determine the speed the platter is spinning at so it goes too fast.
 
I'm not confident that I can spot the problem. There are a lot of solder joints on that board. Do you think it would be better to try and locate a replacement PCB from another deck instead?
 
Havinmg had extensive experience of fixing Technics direct drive runaway speed issues, I would suggest you start with caps in the FG (frequency generator) circuit. The rotational / position sensors W1, W2, W3, W12, W22 and W32 all pass through capacitors before hitting the drive IC AN630U. The caps I would concentrate on are C6, 7 and 8 and also C17, 18 , 19 and 20.
 
Your knowledge on this subject is impressive. I don't understand how this turntable works, but its pretty clear that you do. I have never replaced capacitors before. To follow your advice, the Tecnics manual indicates that I need to obtain and install three capacitors of type ECEA50N1, one of type ECQM1H472KZ, and three of type ECEA50Z1. Is it possible to use these old Technics part numbers to find replacements, or do I need to use the values stated in the manual to find equivalent replacements? Can you direct me to a source that would allow searching for capacitors of equivalent values?
 
mrwood said:
Your knowledge on this subject is impressive. I don't understand how this turntable works, but its pretty clear that you do. I have never replaced capacitors before. To follow your advice, the Tecnics manual indicates that I need to obtain and install three capacitors of type ECEA50N1, one of type ECQM1H472KZ, and three of type ECEA50Z1. Is it possible to use these old Technics part numbers to find replacements, or do I need to use the values stated in the manual to find equivalent replacements? Can you direct me to a source that would allow searching for capacitors of equivalent values?
Click to expand...

If you look at the actual values of the capacitors as noted on the schematic, you will see that they are mostly pretty common types. Ignore the Technics part numbers for things like caps because all that matters is the capacitance value ( in uF or micro farrads) and the rated voltage.

I think mostly those caps are 4.7 uF 50 volt and you can use literally any brand, some being more reliable than others.

I spent a long time diagnosing a speed issue with my SL-QL1 and it was these types of caps that had failed.

In terms of how the table works, I only understand it in layman's terms. The rotation of the platter causes variations in the magnetic field generated by magnets around the platter and this is picked up, amplified and processed by the main control chip. The failure of caps in this signal chain leave the chip without a reliable signal to compare, so it goes into 'freewheel' .
 
mrwood said:
Thanks. The motor board...Do you need to remove it and check both sides? That is daunting, take a look at all the stuff that is on top of it:

https://www.vinylengine.com/turntable_forum/viewtopic.php?f=18&t=72916

Does it take talent to disassemble?

To spot a soldering problem, do you use a magnifying glass, a bright light, flex the board a little to look for cracks? How do you guys go about it?
Click to expand...


Never flex a PCB. That alone can cause bad solder joints or cracks in the traces.
 
Hi All. I know this thread is quite old, but i have exactly the same problem: on a Technics SL-D3 speed is stable but just too fast...
I checked all solder joints and cleaned pots.
I desoldered and checked capacitors C6, 7 and 8 and also C17, 18 , 19 and 20. They are all OK.
Should i go forward to change IC AN630U, or can i still check something other before ?
Maybe transistors or some other components ?
This problem is turning me crazy...

Thanks in advance for any suggestion!
 
federillo67 said:
Hi All. I know this thread is quite old, but i have exactly the same problem: on a Technics SL-D3 speed is stable but just too fast...
I checked all solder joints and cleaned pots.
I desoldered and checked capacitors C6, 7 and 8 and also C17, 18 , 19 and 20. They are all OK.
Should i go forward to change IC AN630U, or can i still check something other before ?
Maybe transistors or some other components ?
This problem is turning me crazy...

Thanks in advance for any suggestion!
Click to expand...

I would advise caution with regard to replacing the IC controllers etc - I fell into that trap with an SL-QL1. I'm not familiar with the D3 but I can tell you it was replacement of the caps in the FG servo circuit that cured my QL1. Caps can test OK on a DMM or cheap cap tester but they can still be leaky if subjected to higher voltages than a basic test gives them. I would suggest replacing them anyway.
 
I'm glad I found this thread.

Markoneswift - would you take a look at this thread I started:
http://audiokarma.org/forums/index.php?threads/replacing-capacitors.854169/#post-12368199

I posted pictures of the schematic and circuit board of my Technics SL-D2 turntable. It has the exact same problem as this thread owner described (and the same IC chip AN630U).
Can you spot which caps are in the FG servo circuit? I want to start with those (replacing). The list below is what I intend to replace (electrolytic only).

Thanks!

upload_2019-1-21_14-28-39.png
 
Hi all. Finally I have replaced C6, C7, C8 and C18, C19, C20, so all CAPS in the FG servo circuit, I think.
Moreover, I resoldered solder joints in the stator coil part of the board, even if they seemed OK.
Reassembled the TT and tested: behavior unchanged. TT spins too fast in 33 mode and even faster in 45 mode... :-(
Any suggestion ? Could be useful recap all remaining capacitors ?
 
federillo67 said:
Hi all. Finally I have replaced C6, C7, C8 and C18, C19, C20, so all CAPS in the FG servo circuit, I think.
Moreover, I resoldered solder joints in the stator coil part of the board, even if they seemed OK.
Reassembled the TT and tested: behavior unchanged. TT spins too fast in 33 mode and even faster in 45 mode... :-(
Any suggestion ? Could be useful recap all remaining capacitors ?
Click to expand...

I ended up recapping the entire board (electrolytics only) and still had the identical problem. I suspect a bad AN630U IC. I ended up buying a used board on ebay and recapped that one when I received it. It works great now.
 
I was thinking trying to put a resistor (I would initially try 10K or 20 K) in series to variable resistor VR1 (speed control for 33 speed, 50Kohm ) to increase resistance and thus lower minimum speed that can be set by VR1... Do you think it should work this way ?
 
federillo67 said:
I was thinking trying to put a resistor (I would initially try 10K or 20 K) in series to variable resistor VR1 (speed control for 33 speed, 50Kohm ) to increase resistance and thus lower minimum speed that can be set by VR1... Do you think it should work this way ?
Click to expand...

Others on this forum are more qualified than me to comment - but I would think your issue is in the speed chip (IC) and that applying resistance external to that chip in the hope of "slowing" the platter down will just produce a negative feedback in the sensor - it will just try to speed up again and do other damage with the higher current. I'm just guessing however. I look forward to what others write that will be more likely what may happen.
 
I tried... At first attempt I replaced resistor R12 (which is in series to variable resistor VR1,speed control for 33 speed), 39K, with 60K resistor.
Turntable speed decresed a little... Second attempt with130K resistor: about 50 RPM. With 270K resistor I reached about 33 RPM, measured with smartphone app. Speed can be fine tuned with pitch adjustment knob and strob dot pattern seems to be oscillating but quite stable.
I don't know... I am torn about leaving TT this way and replacing even resistor in series to VR2, to reach right speed even for 45 RPM, or trying to identify the real problem, assuming that it is possible... Maybe if this is behaviour for my TT, the issue could not be in the AN630 IC ?
 
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