Technics SL-1210MK2 - weird speed problem

[shanezn]

I made a video detailing the issue and SDS's awesome fix.


YouTube

 

[DJ Caverna]

same break trimpot at maximum problem on start TT

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

-> i was have a Pair of SL-1200 MK2 and only one sl-1200 mk2 with this same issue on start/stop (ON START)

sometimes when im was push start turntable the platter spin back 5cm and go forward ok without problem... it was not aways...
and i discover something: when im decrease a break on TRIMPOT to less force the problem was never happend again ..

maybe some capacitor or resistor with problem on start/stop line ... one mk2 dont happend and other happend with break near to maximum

you replace An6675 and An6680 and this problem not gone .. i assume that the 2 Chips is not responsable for this issue

maybe C214 (10v with 100uf) or D204A or R215 (that feed the trimpot with voltage)

all the best for all

 

[SDS]

Imageshack has decided that what was once free should now be paid for, so the scope screenshots in post #74 are gone.
Updating by re-posting image here, original post can't be edited.

Here's the comparison.

Another thought is that maybe the output driver on pin3 in the AN6680 goes faulty then changing R307 comes as a solution but IC201 could be the real cause, I have none at hand to check.

 

[oer23]

Hello their. I'm looking for a complet datasheet of this IC. Somebody can hepl me?
Or is someone find a solution to make the replacement of this obsolete IC?
Regards.

 

[wavejump]

Hi,

I am a bit late here but I thought I give it a try.
My Technics 1210 MK2 has also this weird speed problem but right from the start without warming up.
If the platter is not touched it behaves normal but if I manualy slow down the platter with my fingers the weird speed problem happens.

Should I also start with replacing R307 and D301?

 

[Netlist]

Should I also start with replacing R307 and D301?

They should be easy to measure.
Ususal suspects are IC201 which is AFAIK obsolete, the motor coils or the pitch fader.

Edit: IC101 & IC201 (AN6675 & AN6680) are all over the place but non available at trusted sources, so be careful with fake parts.

Hugo

 

[wavejump]

Thanks for the reply!

When I disconnect the pitch from the mainboard the platter starts to behave weird right from the start without touching it.
If the pitch is connected, the problem appears only when I adjust the speed by pushing/touching the platter.
I will try to find the problem with a multimeter.

 

[wavejump]

I changed the resistor R307 to a 10K resistor since the old one didn’t show nearly 2,7K - I think it was only about 1K. Still the same problem.

Gonna buy a new diode and test it again.

 

[Netlist]

R307 should be 2.7k. Did you measure it out of circuit? And why did you change it to 10k?
Also keep in mind the diode is a zener 5.1V, 0.5Watt.

Hugo

 

[wavejump]

I read it here in the thread to change to it 10K. But but I kept the old one and will test it with a new diode. Thanks for your reply

 

[Netlist]

Do check for bad solder joint too on IC's and especially Q201.
It is true that in some schematics they use 10k but if the original is 2.7k...
I don't know why it has been changed so I can't comment on it.

Hugo

 

[wavejump]

I tested and compared the zener diode D301 today with a properly working 1210:

Working 1210 diode: 0.50V
Broken 1210 diode: 0.39V

Do I have to change the diode in this case?

 

[Netlist]

I'd say yes or you could swap the good one to try.

Hugo

 

[wavejump]

I just swaped the diodes and the problem still remains. Any ideas what I could check next? I checked also the X201 and it is in good condition.

 

[Netlist]

You swapped IC201? You checked the solder joints?
I cannot think of anything else at the moment except the fader or the motor coils.

Hugo

 

[wavejump]

I’ll check tomorrow thanks!

 

[antonman]

Hi everybody!

Looking for some expert advice. My problems looks like this.

To be sure that pitch is not the problem i disconnect it, pins 6 & 7 shorted, so it works without it.

Press start and there is two light movements of dots, then spins ok for some time. Then it starts to slow down and in 15-30 minutes it fully stops. If i press start nothing happens. Then it rests for couple of hours and situation is the same. (But if it rests for 1 hour situation is like in the middle of the process. It turns but too slow).

I start to check like it says in the service manual. First step is 20v on TP5. I have 23,3v there.



I check the voltage on AN6680 and A6675 and i see that on some pins it is more then should be. It should be 15 but there is 18, should be 20 but there is 23. May be it is too much voltage and it starts to warm?

Here is the result of measuring.

Format is

pin / service manual / measurement



AN 6680---------------AN 6675

01 / 2,5 / 2,86----------01 / 2,0 / 2,4

02 / 2,0 / 3,0-----------02 / 2,0 / 2,4

03 / 2,0 / 3,0-----------03 / 0 / 0

04 / 2,1 / 2,1------------04 / 2,0 / 2,4

05 / 3,4 / 3,4-----------05 / 5,0 / 5,2

06 / 3,3 / 3,4-----------06 / 6,6 / 6,8

07 / 0 / 0,01------------07 / 0 / 2,8

08 / 0 / 0,2------------08 / 5 / 5

09 / 10 / 10,3----------09 / 0 / 0,2

10 / 9,4 / 9,7-----------10 / 15,0 / 18

11 / 0,2 / 0,6-----------11 / 15,0 / 18

12 / 0 / 0,2------------12 / 15,0 / 18

13 / 0,3 / 0,2----------13 / 15,0 / 18

14 / 0,5 / 0,7----------14 / 15,0 / 18

15 / 8,1 / 8,3----------15 / 20,0 / 18

16 / 1,2 / 2,2----------16 / 0 / 0

17 / 5,0 / 5,2----------17 / 15,0 / 18

18 / 2,2 / 2,3----------18 / 20 / 23

19 / 7,0 / 8------------19 / 20 / 23

20 / 5,9 / 6,2----------20 / 20 / 23

21 / 0,2 / 0,2 ----------21 / 20 / 23

22 / 3,2 / 3,3----------22 / 0,2 / 0,2

23 / 3,2 / 3,3----------23 / 20 / 23

24 / 2,8 / 2,9 ----------24 / 1,7 / 2,4



Any opinions?

 

[Netlist]

I would suspect an electrolytic cap.

Hugo

 

[antonman]

Which one? C1?

 

[Netlist]

Can't tell, it's a gut feeling based on your discription.
Could you post a clear birds' eye view of the PCB?

Hugo