SL 1200 MK2 reference voltage

turning japanese
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john_cgn
Germany
Posts: 4
Joined: 13 Nov 2019 12:52

SL 1200 MK2 reference voltage

Post by john_cgn » 13 Nov 2019 13:17

hello,
i have a problem with my sl1200, its not starting probably and rotating with low torque.
i checked the reference voltage of TP5 which is 10V instead of 20V.
But voltage on TP3/ J1 before Q1 is still ok with 38V,
Voltage after R1 before Base of Q2 is just around 10V (instead of 21.2) which results in a low base of 10V for Q1, so the Emitter of Q1 can not be bigger than 10V. (Base+0,6V=Emitter)

i already changed Q2 with no result.
R1 is also tested 5,6K.
Zener Diode is also testet ok.

any suggestions? all the IC are working with 10V instead of 20V. could it also be a problem with the ic's?
thanks

sylvain999
senior member
senior member
Posts: 367
Joined: 10 Mar 2012 22:51
Location: Blainville Quebec

Re: SL 1200 MK2 reference voltage

Post by sylvain999 » 13 Nov 2019 15:49

Check if the cue light has been changed, and if the rubber stopper is still on the pop up. If the rubber is missing, the wires may have been shorted or partialy shorted, and may have fried Q 201 and or Q202 and sometimes D301.

john_cgn
Germany
Posts: 4
Joined: 13 Nov 2019 12:52

Re: SL 1200 MK2 reference voltage

Post by john_cgn » 13 Nov 2019 16:28

the cue light ist working normally, but all lights(cue/on,off/33,45) a darker compared to my other technics because of the lower voltage...

john_cgn
Germany
Posts: 4
Joined: 13 Nov 2019 12:52

Re: SL 1200 MK2 reference voltage

Post by john_cgn » 13 Nov 2019 16:41

if i disconnect the cue light completely the voltage is still around 10V. so as all users are connected in parallel after the voltage regulator the problem must be somewhere else, but i don't know what to do next.

sylvain999
senior member
senior member
Posts: 367
Joined: 10 Mar 2012 22:51
Location: Blainville Quebec

Re: SL 1200 MK2 reference voltage

Post by sylvain999 » 13 Nov 2019 18:29

there is a small piece of pvc insulation on the black cue light, where it enters the tube, is it there? Sometimes the wire insulation is so lightly damaged you can't see it. Even if you unplug the light, the damage is done. I guess you have a multimeter with diode check, test all transistors for any short. If transistors are o.k. i' d disconnect AN 6675 and AN 6680 DC voltage input pin from the circuit and check if that brings back the 20Vdc.

john_cgn
Germany
Posts: 4
Joined: 13 Nov 2019 12:52

Re: SL 1200 MK2 reference voltage

Post by john_cgn » 13 Nov 2019 20:50

Thanks for your quick response and help.
I changed q3 as well, because that was the only one i did not change.. and That solved the problem, voltage is back to 20v, lights are bright again, turntable has complete torque etc.
Thanks for all the information in this forum!

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