Technics SL-1100 weak motor

[L0rdJim]

Hi, I have been lurking the forum for quite some time, but have never posted myself. I want to apologize beforehand, that my first post is asking for help. I found a nice technics sl-1100 turntable that seemed to be in reasonable shape for a good price (120$us). Now the problem is that the motor seems to be weak. It doesn't start by itself on the 33rpm settings. It does start spinning with a little help, and vinyls sound good. Anybody has any suggestions if this can be fixed, or is the motor dying. Help appreciated.

here's a picture, taken in the garage with my phone. sorry for poor quality



and i uploaded a video on youtube, demonstrating the problem

http://www.youtube.com/watch?v=SGMtjDRSOgE

[Alec124c41]

Take the platter off, but mark its position with the center, so you can put it back in the same position.
There is an oil hole there into which you should put a couple of drops of light machine oil.

Cheers,
Alec

[L0rdJim]

Thanks for the reply Alex. I have put 3 or 4 drops of light engine oil into the hole and let it spin for a while, but it is still missing alot of torque. When it spins i can make the platter stop very easily by touching it with my finger. to make it start again i give it another light push with the finger. rpms are ok, just no torque on the motor.

[ATHERMOS]

A direct drive usually has a very high starting torque , more so in the case of a Technics DD motor which has a core (not a coreless motor).Decreasing the voltage applied to this motor would decrease the torque rather than affecting its speed (within limits). So the thing to look out for is the power supply,the smoothening capacitor might have gone bad over the years or something else might be wrong , say , if there exists a voltage selector, the turntable may have been set to work at a higher voltage than the existing mains voltage.

[L0rdJim]

Thanks Athermos. I downloaded the pdf service manual for the sl-1100. Under the trouble shooting guide it says as follows:

TROUBLE E: Turntable, after stopped by hand, will not tur or stars turning but will stop soon.
SOLUTION: 3-phase switching circuit defective *Replace printed base assembly.

Now that's not really the problem, cause once it starts spinning it seems ok, just no torque.
I also carefully unscrewed the motor and meassured the voltages at the plugs that connect the motor to the board, and some read 19.1v and one only reads 14.5v. Anybody knows if this voltages seem correct or might be faulty?

regards,
Ingo

[ATHERMOS]

Please refer to the schema downloadable from the same page , and tell me where have you measured the voltages. Also please check C14 (470uf/50v), you may replace it by a new 1000uf/50v (may be procured from any electronics spare parts dealer)and compare the results.

[L0rdJim]

I will do that Athermos. I haven't been at home, but will measure the voltages again and tell you exactly which are the pins as soon as i get home.

[L0rdJim]

Please refer to the schema downloadable from the same page , and tell me where have you measured the voltages. Also please check C14 (470uf/50v), you may replace it by a new 1000uf/50v (may be procured from any electronics spare parts dealer)and compare the results.

sorry for not replying earlier. i wasn't at home for a couple of days.

i took off the platter and the motor started the turntable, as if i was going to play a record and measured the pins that connect to the motor. the pins that are marked in red had 19.5v, but the voltage wasn't stable, it would blink (like come and go) and the one marked in blue would vary from 14v to 18v.

i also looked at the 470uf/50v capacitor. from the outside it looked ok. i'm going to find a replacement capacitor. it's kind of hard to find the same type with the - and + connector on the top and button, so i just going to buy a normal one and figure something out. i have a 2200uf/50v nichicon, that one should also work yea?



NOTE: i just tried with a 2200uf capacitor and still no change. i also encountered some inconsistency in the rpms today while playing a record, then after a while it played ok again. when i run the motor with the platter it doesn't seem to spin smooth, like if it was coming and going.

[Alec124c41]

Have you cleaned the speed adjustment pots?
Cheers,
Alec

[L0rdJim]

hi alec

no i haven't cleaned the pots. will give it a try

[ATHERMOS]

Saw your post earlier this week but was waiting for the weekend to reply.
Please locate VR1 (10K )on the PCB and adjust it and note its effect on the motor torque.VR1 controls the power to the motor. Meanwhile studying your reports of fluctuating voltages and shall get back.