Technics SL-1200MK2 brake only working sometimes

[hyperplanar]

Hey y'all, I was hoping that the members with experience repairing electronics could chime in here.

I bought a SL-1200MK2 secondhand from a local DJ as my first turntable and have been using it for some time now. I decoded the serial number and discovered it's nearly as old as I am

I installed/aligned a new cartridge and also acquired an OEM mat after buying it. For the most part, everything seems to work great; however, the braking function works inconsistently, and trying to fix it has left me scratching my head. To clarify, the braking function is what is activated whenever the stop button is pressed--it applies an impulse of torque in reverse to the platter in order to decelerate it as quickly as possible. The length of the impulse is adjustable using a pot underneath the platter, which I have already tried fiddling with.

The problem is that the braking only works sometimes. About half the time, the braking works properly; a quarter of the time, the braking does not do anything at all, and another quarter of the time, the braking is way too strong and sends the platter spinning backwards.

I have a multimeter and a soldering iron (and I am currently at the point on the Dunning-Kruger scale where I would definitely bust my turntable if I tried to investigate further by myself...)

Your advice is appreciated!

 

[JSmith]

SL-1200MK2

Hey mate, congrats on owning the best DJ mixing turntable ever made... wish I still had two!

It would be great to see more DJ's get back to the real roots of mixing. Some of the old DMC DJ comps were just amazing.

This may assist;

https://www.fixya.com/support/t11492000-platter_reverse_when_stopping

https://www.vinylengine.com/turntable_forum/viewtopic.php?f=16&t=62235#p494695

JSmith

 

[hyperplanar]

Hey mate, congrats on owning the best DJ mixing turntable ever made... wish I still had two!

It would be great to see more DJ's get back to the real roots of mixing. Some of the old DMC DJ comps were just amazing.

This may assist;

https://www.fixya.com/support/t11492000-platter_reverse_when_stopping

https://www.vinylengine.com/turntable_forum/viewtopic.php?f=16&t=62235#p494695

JSmith

Hey JSmith, I can only agree! I'm happy I went with a SL1200, battle scars and all, instead of buying a new turntable. It's built like an absolute tank and feels like owning a piece of history

Thank you for the links... Unfortunately, I've already had a look at these in the past. The problem is not the brake calibration per se--instead, it's how the braking is inconsistent, where sometimes it works, sometimes it doesn't, and sometimes it's too strong.

I suppose what that one poster on vinylengine said about checking the resistance of the brake pot is worth looking into, but before I proceed, it would be nice if somebody could walk me through the steps for doing so using a multimeter (where to connect the leads and what setting to use on the multimeter). Really don't want to break the thing!

 

[JSmith]

feels like owning a piece of history

Nah, you do now own a piece of history Bro... your officially ridin' the wheels of steel;

https://happymag.tv/technics-sl-1200/

Imagine the price of this baby;



The MKII though was particularly well designed.

In relation to the issue with the turntable, if you're not confident in attempting DIY any further, take it to someone who knows what they're doing and has the experience to fix it for you. It's too awesome to stuff up...

Hopefully not too expensive either... not sure if near you;

https://www.georgemeyer-av.com/turntables/technics-turntable-service-repair/



JSmith

 

[restorer-john]

The SL-1200mk2 brake should be adjusted with the supplied rubber mat and a typical record on the unit. Yes, I know that is difficult, but that's what you need to do. If you use a slip mat and no record and tweak the brake pot, it will behave differently for each record.

Even a perfectly adjusted 1200mk2 will sometimes kick back a little, over-run a little, or not stop dead. It is the variations in record mass, speed (33/45) and the actual timing of the stop/start button. I have several of the decks BTW.

 

[hyperplanar]

The SL-1200mk2 brake should be adjusted with the supplied rubber mat and a typical record on the unit. Yes, I know that is difficult, but that's what you need to do. If you use a slip mat and no record and tweak the brake pot, it will behave differently for each record.

Even a perfectly adjusted 1200mk2 will sometimes kick back a little, over-run a little, or not stop dead. It is the variations in record mass, speed (33/45) and the actual timing of the stop/start button. I have several of the decks BTW.

Hi John, thanks for your input. I did adjust it with the OEM rubber mat and a record on top, as I figured it should be adjusted for the typical use load weight (I only use it to listen to records, I don't DJ with it). It's good to hear that some variance is normal, but I'm 99% sure my unit isn't behaving within normal tolerances... When I say it brakes too strongly sometimes, I mean it does it strongly enough to rotate the platter backwards more than three revolutions. And when the brake doesn't work, it literally doesn't work--the platter stops rotating slowly the same way it would as if you just unplugged the power cable while it was playing.

So I'm pretty sure it's not the adjustment of the brake pot that's the issue here--I suppose the pot could need replacement if its resistance is erratic, but how do I check for this? Any other ideas to what the culprit might be if that's not it?

 

[hyperplanar]

In relation to the issue with the turntable, if you're not confident in attempting DIY any further, take it to someone who knows what they're doing and has the experience to fix it for you. It's too awesome to stuff up...

Hopefully not too expensive either... not sure if near you;

https://www.georgemeyer-av.com/turntables/technics-turntable-service-repair/

Thanks, I don't live in LA proper (in the county though) but these guys are located close enough. If I can't resolve this with your guys' help, I'll probably take it there, but I would definitely prefer to fix this the DIY route if possible in order to learn a thing or two about my turntable works and repairing electronics. Also would be nice to save some money as always!

It's not so much that I'm not comfortable in trying to fix this myself; I have cursory knowledge on the fundamentals of electronics and am decent at soldering, having done a bunch of stuff with a microcontroller on a breadboard in college a few years ago, but I've never actually tried to fix something like this, so some sanity checks would be appreciated

 

[restorer-john]

Hi John, thanks for your input. I did adjust it with the OEM rubber mat and a record on top, as I figured it should be adjusted for the typical use load weight (I only use it to listen to records, I don't DJ with it). It's good to hear that some variance is normal, but I'm 99% sure my unit isn't behaving within normal tolerances... When I say it brakes too strongly sometimes, I mean it does it strongly enough to rotate the platter backwards more than three revolutions. And when the brake doesn't work, it literally doesn't work--the platter stops rotating slowly the same way it would as if you just unplugged the power cable while it was playing.

So I'm pretty sure it's not the adjustment of the brake pot that's the issue here--I suppose the pot could need replacement if its resistance is erratic, but how do I check for this? Any other ideas to what the culprit might be if that's not it?

It won't be the brake pot.

Try replacing C214 16V 100uF electrolytic. Adjust the brake and report back.

 

[hyperplanar]

It won't be the brake pot.

Try replacing C214 16V 100uF electrolytic. Adjust the brake and report back.

Thanks, I'll have to order one and wait for it to arrive. Will this cap be good, or is there a better one for this application?
https://www.digikey.com/en/products/detail/nichicon/UPW1C101MED/589520

Anything else I should order at the same time?

 

[hyperplanar]

It won't be the brake pot.

Try replacing C214 16V 100uF electrolytic. Adjust the brake and report back.

Hi John, I replaced C214, but unfortunately the problem still persists

Any other ideas?

Hmm, I spot some Elna caps in here, presumably someone’s already mucked around with the PCB before me.

 

[restorer-john]

Can you make a quick phone video of the issue and link to it?

Do a quick start- run- stop video say three times in succession on 33 and 45. I wanna see what it is doing exactly.

 

[hyperplanar]

Can you make a quick phone video of the issue and link to it?

Do a quick start- run- stop video say three times in succession on 33 and 45. I wanna see what it is doing exactly.

Sure, here's the link:

https://imgur.com/olD3Jjd

I don't know what the law is called where you have a rattle in the car/have a problem with your computer/etc but when you show up to the mechanic or the IT department, the problem goes away, but I had a bit of that while recording this video, because it seems to happen much less often than before now It's funny because I'm usually on the receiving end of that law...

I was using the turntable for the past couple hours so maybe being warmed up had something to do with it. The turntable doesn't seem to reverse anymore, but you can still see a couple times when I press stop where it seems to cog and suddenly spin faster before slowing down, or come to a stop slowly.

 

[frabor]

I started refurbishing my país of sl-1210. Today was tonearm headshell pins cleaning and brake adjustment. What i get is some lack of consistency, most of the times it stops perfect, some times goes back a couple of black strobe dots, some time it will take about a quarter loop to stop. It matches perfectly what restorer-john said, tks for the info, i panic for a minute wondering if i needed a new board. Restorer-john said "Even a perfectly adjusted 1200mk2 will sometimes kick back a little, over-run a little, or not stop dead"

 

[frabor]

After i Adjusted the braking with a cork platter, and following the suggestion of John-Restorer, i changed to the thick rubber mat. Came out perfect. But when I placed back the cork, much lighter, the platter spin back every time. It seems that an adjustment with a mat may not work fine with a different mat.