Technics SL-1210MK2 - weird speed problem

Well... I found the culprit. I atually didn't know that having the Brake pot to the maximum clockwise position was actually making the platter goes backwards... Had to go to the maximum counterclockwise position to calibrate it properly. It now doesn't spin back anymore and doesn't move either when I turn the deck on !

Cheers
 
Thanks for the update on the vintage turntable.

Other (good) repair technicians I know have fixed this issue heat sinking IC201, I would not bother.

The .PDF service manual I have states both 2k7 and 10k ohm for R307.

I spent a while investigating on that fault, charged quite a bit of cash, I've had no feedback from my customer who uses his turntables intensivley, I take that as good news knowing that I would have heard from him if there had been a problem.

I only settled for that solution because the service manual mentioned 10k for R307 and the measurements agreed, I'm also convinced it's the most reliable fix suggested so far although the waveform could be cleaner.

Switch the oscilloscope on, improve further...

hi SDS, i have the fluctuating pitch problem at -8 on my 1210 mk5 and i want to try with this 10k resistor, but could you tell me how much the wattage of this 10k resistor must be? 1/4w? 1/2w? 1w?
i’ve also read the posts regarding the zener diode and the an6680 ic, so i’m thinking to buy also the zener diodes just in case the only resistor couldn’t resolve the problem.
i read the zener diode must be 5.1V and 1.3W, is that right?
i found a shop that sells zener diodes 5.1V but 5W or 1W, could be good as well buying the 5W version or not?
thanks in advance
 
Quick update,

I had 2 in for repair with the same problem, the second was fussier, looking trough the service manual on various schematics you can either read 2k7 or 10k for R307.

The turntables I have are from 2006 and had 2k7 for R307, replacing this by 10k solves the problem much better than finding a good 5.1V zener for D301 as this turntable would loose lock with voltages of 5.3V on D301.

With 10k the fall time and low-level noise of "FO" (Pin1 of IC301/IC302 or pin3 of IC201) are much better.

The odd thing is that with a trimpot in place of R307 I find that 2.7k ohms is about the value needed for problems to appear, maybe Matsushita decided their product was much too reliable for the present day and found a quick workaround for making it less reliable with minimum modification. Maybe not, but then someone will have to explain why R307 should be 2.7k


Can someone with a much older SL-1200mk2 confirm the value of R307?

SDS: Thank you for sharing this. I have his same exact issue with my 1200mk5 and thanks to you I think we have the solution. The only issue is that I have never replaced a resistor before. However I have rebuilt PCs and laptops so not afraid to get under the hood. Would you be able to put together a video on how to get this fix done. I have no issues paying you for this video via PayPal you as long as it's a reasonable price. I would need to know exactly what tools to buy, preferably with links to US stores such as eBay and Amazon in addition to the step by step instructions in a video if possible. Let me know please.
 
I would have done a short video no problem if I had a turntable at hand.
I've stopped business for the time being and even when I was still at work these turntables didn't show-up often.

All you need basically is the 1/4w 10k ohm resistor, small wire cutters, a decent soldering iron (even for occasional work and beginners I'd really recommend an adjustable iron) and a little 60%Sn-40%Pb solder.
Some desoldering wick is a good idea too.

Unplug turntable, remove platter (and place safely away from magnetic objects), remove plastic cover.
Disconnect all the connectors to the PCB that you can, unscrew power transistor that is heatsinked to body, unscrew PCB and motor stator.

Set different screws as side by length noting where they go if needed.

Use desoldering wick to remove the original resistor, place and solder the new one, cut legs close to the PCB.

Reassemble doing previous seteps in opposite order, it's a good idea to fit all screws to PCB/stator loosely first then tighten them all starting from the stator.
Don't forget to fasten the power transistor, then reconnect and test.

(Oh, don't forget to film...)

I think you may find some YouTube videos looking for the SL-1200mk2.
 
I would have done a short video no problem if I had a turntable at hand.
I've stopped business for the time being and even when I was still at work these turntables didn't show-up often.

All you need basically is the 1/4w 10k ohm resistor, small wire cutters, a decent soldering iron (even for occasional work and beginners I'd really recommend an adjustable iron) and a little 60%Sn-40%Pb solder.
Some desoldering wick is a good idea too.

Unplug turntable, remove platter (and place safely away from magnetic objects), remove plastic cover.
Disconnect all the connectors to the PCB that you can, unscrew power transistor that is heatsinked to body, unscrew PCB and motor stator.

Set different screws as side by length noting where they go if needed.

Use desoldering wick to remove the original resistor, place and solder the new one, cut legs close to the PCB.

Reassemble doing previous seteps in opposite order, it's a good idea to fit all screws to PCB/stator loosely first then tighten them all starting from the stator.
Don't forget to fasten the power transistor, then reconnect and test.

(Oh, don't forget to film...)

I think you may find some YouTube videos looking for the SL-1200mk2.

SDS: Thank you so much for the reply. Would this kit work?
Amazon.com: Magento's Superb Quality Soldering Iron - 14 Extra Pieces for Easy & Safe Use at Work and Home: Home Improvement

I would purchase the wick separate since it does not include it.

And would this be the correct resistor to buy?
5pcs 10K Ohm 1/4W 0.25W 1% Metal Film Resistor Yageo Free Shipping | eBay

Thanks again SDS. Much appreciated.
 
Yes, all that should be fine. I doubt the iron is great quality but if it's just for the occasional (or single) job it's not worth going for expensive stuff.

Your kit has a desoldering pump so you should be able to do without the wick. Wick is just a bit more efficient at the job and you have less chances of causing damage than with a pump.
 
I overlooked the zener question.
Well buy them if you must but you'll not need them unless you create a short somewhere.
1W or 5W either should do, as it comes from the factory the turntable is very picky for the zener anyway. It has to be a little on the low side of 5.1V and have the sharpest knee and temperature drift possible... Not worth the bother... Try the resistor you'll be OK.
 
Hi guys. I recently grabbed my 1200 Mk2 out of the garage as i had left it in it's broken state for quite a few years. I'll run through some of the recent issues i've had below and tbh i can't remember the exact problem but it was something to do with erratic speed hence i found this thread.
One question i have is regarding the 3 ceramic capacitors that are soldered to the underside of the main board. Does anyone know if these are supposed to be there? This deck has had some work done to it in the past, one of the ceramics i mentioned above has definitely been replaced and one of the others had a leg knocked loose and i can't be 100% certain where to solder it back on. It appears to be soldered to legs 8 & 10 of ic 201 (definitely leg 10 as that one remained in place).
I can provide more detail on these ceramic caps if anyone is interested.
So when i went to turn it back on after all these years i noticed F2 was blown so i fixed that then when i turned it on the red light was on for a second then out. I found that Q3 had a short so i've ordered another. I am hoping this will give the correct voltages into the transistor D389 that is held down off board via a clip. Currently it has 47V i think and 2v where the 20V should be. But the other leg should have a fairly high dc voltage but there is almost nothing there (suspected due to Q3 being blown) But i have ordered a spare D389.
I am wondering if Q3 blew because i pressed the start button without the platter being in place. Or if it was due to the short on the track lamp as mentioned below.
I will also replace D301 and D3 as i shorted it by mistake when trying to check the voltage, It might be ok but it's easy to replace. I assume that D301 is the same value as D3.
I guess i will also replace the 2k7 for a 10k while i'm at it as it seems the thing to do.
One of the main ic's has a heatsink but ic 201 does not, i guess thats standard and sounds like it shouldn't need it once the 10k resistor is in place.
I'm waiting for Q3 to turn up and i should have some zeners knocking around. I always find it a mission to read the value of a zener and too much of a mission to test it to find out.
Hopefully it's been written on the baggies i've got in stock :D
One tip for anyone trying to replace Q2 or Q3 is to run a piece of wire under it (between the legs, i used thin stranded) then form a loop around the transistor by soldering the wire in a loop while leaving a long tail to pull with. Then heat the the legs from the underside with your iron while pulling gently on the wire loop you made. Once the solder has melted (using the iron at an angle with a decent molten blob to get all the legs at the same time) The transistor will come away. Since this is a tricky spot to get to. If your solder sucker sucks or you can't be bothered to setup your main sucker station if you have one, then this is a fast work around.
The other crazy thing i found which might have blown the components or caused the issue was that a previous technician(?) had removed the track lamp or rather taken the wires from the lamp and joined them together forming a dead short. The other thing i found interesting was that rather than just using the track lamp microswitch to complete the circuit to turn on the lamp they use the switch to engage a high value resistor to turn the lamp off. The closing of the switch shorts the resistor and lets the current flow again. I guess this is because it is more reliable than the switch, incidentally i measured the resistance of the switch and it was all over the place and needs a good clean up, if i can get any spray cleaner or wd in there, i'll try.
Other thing i wanted to ask is if anyone has ever changed the track lamps for led's. These lamps blow all the time, they are expensive to buy and replacing them is a ball ache.
I must have around 8 or 10 1210's and the one 1200 and most of the track lights are blown.
 
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I would like to IMMENSELY thank you, SDS. You are the man.

SDS, I would like to second that IMMENSELY!

I had the same problem with one of my MK5s as well. I was about to change D301 (for no real reason, the voltage seemed fine, but I wanted to try) and checked a last time in this thread; I had ordered a Zener Diode a while back and wanted to change it now.

I changed R307 instead to 10K (which I had at home anyway), and now the pitch works like a charm. Let me know if you are ever in Munich, I'll invite you for a beer.

For curiosity: Is there anywhere a description what R307 does? :confused:

Anyway, thumbs up, and happy spinning!
 
Hello!

I just noticed the same "weird speed" while mixing some records the other day.

I have a Technics SL-1210 MK2, that has been functioning perfectly until now.

The platter suddenly speeds up or slows down randomly at pretty much any pitch in between -8 to +8 (However the platter dots show highest irregularity at -6 to -8).
Kind of like there would be a ghost touching the record lol.

At first i was set on replacing the AN66880, but having seen the success of the method provided by SDS i'm keen on going his route.

The problem is i don't quite understand what parts i should replace with what.

As i don't own a manual for my turntable i'm quite lost on what the r307 is. And what i should get to replace it with.

I can't believe this thread is still active in 2020.
Thanks
 
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Sounds like you may have a dead electrolytic somewhere. If you have a scope, the power supply would be worth looking at; otherwise the servo loop would also be of interest (i.e. position / speed detection sensing + amplification in particular, they're calling this "FG"). A heat gun or even a hairdryer may help tracking down possible culprits.

There also are pitch +/-0 adjustment and pitch range adjustment trimpots which may appreciate a drop of DeOxit. Does the pitch itself work smoothly?

VinylEngine has service docs. (As well as an ongoing thread on stability issues, btw.) There are plenty of scope waveforms, but a frequency counter of some description (even if just in a fancy multimeter) would also be helpful.

It would be interesting to know why the R307 bandaid fix works - it could simply be a degraded driver in the AN6680, of course, but an unstable IC302 Vcc due to e.g. R304 having gone high (or maybe a dried-out C306) wouldn't help.

I think stability problems can be caused by multiple things in this circuit, and pinpointing the culprit is not always easy.
 
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I would have done a short video no problem if I had a turntable at hand.
I've stopped business for the time being and even when I was still at work these turntables didn't show-up often.

All you need basically is the 1/4w 10k ohm resistor, small wire cutters, a decent soldering iron (even for occasional work and beginners I'd really recommend an adjustable iron) and a little 60%Sn-40%Pb solder.
Some desoldering wick is a good idea too.

Unplug turntable, remove platter (and place safely away from magnetic objects), remove plastic cover.
Disconnect all the connectors to the PCB that you can, unscrew power transistor that is heatsinked to body, unscrew PCB and motor stator.

Set different screws as side by length noting where they go if needed.

Use desoldering wick to remove the original resistor, place and solder the new one, cut legs close to the PCB.

Reassemble doing previous seteps in opposite order, it's a good idea to fit all screws to PCB/stator loosely first then tighten them all starting from the stator.
Don't forget to fasten the power transistor, then reconnect and test.

(Oh, don't forget to film...)

I think you may find some YouTube videos looking for the SL-1200mk2.


Hi SDS. I literally just signed up to say THANK YOU ! I have never soldered in my life but this worldwide lockdown has actually forced me to learn new skills. I replaced the 2.7k resistor with a 10k Ohm and my 1210 MKII is working flawlessly again. I bought the Zener Diode as well but decided to just try the resistor fix first and it did the trick. Everyone kept telling me the pitch fader needed replacing and I had a suspicion this wasn't the case. Really glad I came across your awesome fix. Thanks again for a very informative and educational post :)