Technics SL-1210MK2 - weird speed problem

I have a strange problem with an SL-1210MK2 turntable. Things work perfectly when turned on - rotation speed is stable, pitch control works fine, sound output is fine.

A couple of minutes after turned on and started, the platter starts "losing it" - speed jumps up and down when the pitch control is near -8%. At this point the pitch control works fine in the range -6% to +8%. The speed jumps slowly spread to the rest of the pitch control range and maybe 10 minutes after the platter is started, it is just rotating really fast.

Changing the pitch control slider with a new one (I had a spare) makes no difference. The voltage selector is on the correct setting (220V).

Any idea where this problem could be?

thankful for any suggestions,
m.
 
hi m,
i have had this problem with that model on 2 occasions, inttermitant speed and speed suddenly increasing.
Around the motor there is a sensor /servo coil, this is a printed flexible circuit board coil that terminates in 2 vertical pins/wires soldered to the main board, at the point where the wires attach the circuit becomes broken. you will have to take out the main board to inspect this part and then it is not ovious. on one occasion the part measures ok but when assemled was causing problems, (crack in the coil).
the good news is that this part is availible as a spare from technics, sorry i cannot give you part number or drawing as i have lost my service manual.
regards
bob
 
May be true what others wrote. But many years I, service Tehics ,westax, omnitronics, gemini , turntables. Many DJ's have same problems in SERBIA. The main problems is weaknes of MAGNET on botom of plate.The DJ's carring there equipmnent with large loudspeakers boxes, with stong magnets. Try to put if you can new plate. WHAT you mean about that, & the others wiseguys
 
Ex-Moderator
Joined 2003
Hi evgen,

Did you check/resolder the mentioned components in burbeck and my post? If you have a frequency counter you could look if TP27 is stable at 262.08kHz.
Also, but not likely your problem, it happens the trimpot on the pitch control pcb is broken. Look in the manual how to adjust pitch and pitch gain.

/Hugo :)
 
just want to remind my problem, maybe it is differ from first post.

"I have a model SL-1200 Mk2 and it has the problem of speeding up drastically when i move the pitch slider just off of the "0" mark.
It also drops in rpm drastically when the pitch is set just below this position."
 
Ex-Moderator
Joined 2003
Hi evgen,

You said you changed the pitch fader. Are you sure you connected everything correctly? Did you check the trimpot on the fader PCB. It should read 2.7k. Look if the wiper is still in good condition. Other then that, you will need a scope to check IC101 and IC201. I'll have a more in-depth look at the schematic later and will keep you posted.

/Hugo
 
Ex-Moderator
Joined 2003
evgen said:

I did not replace PITCH, it was replaced by SERVICE CENTER. I think they did it good :rolleyes: .
Anyway i want to know how to test IC101 and IC201. I think problem with IC101 or IC201 or SFMZ172-01E.
Needles to ask for the obvious: was this the original problem and if it was, you could return an ask for warranty.
As stated above, you need a scope to measure the IC's correctly.
then with great care you can compare the waveforms with the diagrams in the manual.

magicplastic said:
Every Technics 1210 I have used has had this fault, I reckon its a design error.
Hi magicplastic,
I repair them for longer then I can think of and never had this particular problem. Do you happen to know the answer? ;)

/Hugo