Technics SL-1210MK2 - weird speed problem

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
 
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.

attachment.php


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.
 
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?
 
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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.
 
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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?