SL-120 Replacing Pitch Pots

turning japanese
bbr620
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Re: SL-120 Replacing Pitch Pots

Post by bbr620 » 09 Jun 2018 14:41

Once again, thank you again to all who helped me. I'm a Happy Camper :D :D

The Multimeter was reading 16.9v for the PCB so I've got that sitting bang on 20v now and speed is running spot on after adjusting sub-pots. I also still have the top pots for fine adjusting.

sharkey22
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Re: SL-120 Replacing Pitch Pots

Post by sharkey22 » 10 Jun 2018 15:02

Good job. Enjoy.

p38arover
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Re: SL-120 Replacing Pitch Pots

Post by p38arover » 11 Jun 2018 11:41

See also https://www.youtube.com/watch?v=2VbGif2f-WA

Not for your model but the pitch pots are. Look from about 1:30

bbr620
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Re: SL-120 Replacing Pitch Pots

Post by bbr620 » 30 Jul 2018 21:42

Back again. Thought all was sorted but been too busy with work to get a proper sitdown with turntable. If I play an album, pitch is bang on for first 10 minutes then starts drifting either fast or slow. I can adjust via pitch knob and it's fine for another few minutes then starts drifting again?

Anything else I need to be checking?

Thanks again.

sylvain999
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Re: SL-120 Replacing Pitch Pots

Post by sylvain999 » 31 Jul 2018 09:59

Could be a lot of things. Bad electronics like bad caps or transistor going wild when hot. Could be the speed switch. Or this happened to me a couple of times when cleaning pots, the cleaner would get underneath the male connectors of the board melting the glue and the grime creating a bad contact i had to desolder the pins from the board in order to fix that.They put a strip of double side tape to hold the connectors in place before soldering and the glue melts with time. If liquid gets in there it gets trapped .

bbr620
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Re: SL-120 Replacing Pitch Pots

Post by bbr620 » 31 Jul 2018 10:18

Thanks for the reply sylvain999.

Yes, I suspected something else like the Caps. I've got a chance of another PCB board so I'm thinking, swap in replacement and get original PCB recapped.

Only Caps I'm struggling to get is the 33uF 10v. Can I replace this with a higher voltage Cap, say 25v or do I need to stick to specific voltage?

If you don't mind another question, what is best Caps, was thinking Panasonic or Nichicons, both 105C's but unsure as some Caps are listed as Audio Grade? or can I just get any Pansonics, as long as they are same uF and voltage (or slightly higher voltage)?

Thanks again for your Help..

sylvain999
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Re: SL-120 Replacing Pitch Pots

Post by sylvain999 » 31 Jul 2018 11:57

Can' t go wrong with both panasonic or Nichicon. You can put a 25 volts instead of 10 volts, just make sure the spacing of connectors is the same. Before refubishing the board i would make sure this is not a bad connection or cleaning issue, sometimes it' s faster to create the problem while the speed is stable by touching tapping moving things.

bbr620
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Re: SL-120 Replacing Pitch Pots

Post by bbr620 » 01 Aug 2018 10:45

Thanks again for the Help. Yes, I'm going to give it a good check round for anything loose or intermittant. The spare PCB will be handy for a backup. Once I get things into play, I'll update in case others are having similar issues.

sylvain999
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Re: SL-120 Replacing Pitch Pots

Post by sylvain999 » 01 Aug 2018 11:22

I hope for you it' s not a motor issue. I serviced a couple of these which had the top cover barely touching the coils and creating a short because the thrust plate is worn on the spindle.

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Re: SL-120 Replacing Pitch Pots

Post by bbr620 » 05 Aug 2018 17:04

Well I got a replacement PCB and slotted that in place. Tested Pins 16 & 17 for 18 Volt AC (checking Power Supply) and it's reading around 18 but fluctuating between 17.5 & 18.5, unsure if this is within tolerance or if it needs to be bang on 18 volt all the time.

Went to set 20 Volt DC on pins 7 & 14 and my original PCB is holding steady 20 Volt with a fluctuation between 19.9 - 20.1 but the replacement PCB is reading 16.5 to 23 volt. I've cleaned all pots again but same results. I'm also getting confused with the 20V on pins 7 & 14 as Service manual states 26V??? Any Ideas?

Just another thing I'm unsure about, what is the large T (Oscillator) for? I noticed the adjustment screw is in different positions on each board? Didn't want to touch it until I know what it's for.

Was unsure if this Cap has had it, isn't bulging, any ideas?

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thanks again for the Help..

bbr620
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Re: SL-120 Replacing Pitch Pots

Post by bbr620 » 07 Aug 2018 12:34

All fixed, finally. Ended up replacing Cap C14 and took out the speed selector switch and gave it a proper clean. Hope this helps anyone else with an older Technics.

sylvain999
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Re: SL-120 Replacing Pitch Pots

Post by sylvain999 » 07 Aug 2018 14:35

Glad you fixed it all and learned a lot in the process. Sometimes you have to go back to step one, cleaning the speed switch. This one is not easy to vlean because it' s made of layers.