technics sl150 issues

Graeme · Post by **Graeme** » Wed Nov 06, 2013 10:45 pm

I'd had some speed issues with my sl150.
Ive replaced all caps, cleaned all pots and variable resistors and have been playing around with setting it up.

Hopefully i have attached a pdf of the service manual.

Trying to set the values for vr3 and vr4 have got me pulling my hair out.

Does anyone understand the circuit and could maybe shed some light on this?

It says to set vr3 so there is 50mv at c15 and set vr4 so there is 2.2v at r38.

They seem to effect each other a little. Getting anything remotely stable is very hard.

Ive no idea what the 50mv is for. I got it at a reasonably stable 48mv ish but wherever its set the speed stability doesnt seem effected.

The 2.2v, if this isnt bang stable you get wow. I cant get anything like a stable 2.2v but could get a stable 1.46v.

Speed and stability seem ok like this but it takes a little while to settle.

Should i replace vr3/4? Any other components likely to be causing the issues? I guess i need to check all the voltage test points too now.

Or, am i worrying about nothing and the actual voltage at r38 doesnt matter and the 50mv stability isnt important?

Also, what is the ELM square adjustable box thing? Ive been messing with that too but apart from the extremes of adjustment it doesnt seem to do much.

Thanks

I cant add the attachment, te manual is here http://www.vinylengine.com/library/tech ... 1500.shtml

service manual, not the mkII one.

Graeme · Post by **Graeme** » Wed Nov 06, 2013 10:53 pm

Ok, elm is an oscilator. I guess thats ok then, i just set it back where it was.

Mike H · Post by **Mike H** » Thu Nov 07, 2013 3:08 pm

Yours is the Mk1 then, servo control?

Not allowed to download manuals (not a member)

Graeme · Post by **Graeme** » Thu Nov 07, 2013 3:56 pm

Yes. Ill see if i can find another source for the schematic.

Graeme · Post by **Graeme** » Thu Nov 07, 2013 4:08 pm

Cant find another source for the schematic.

Greg · Post by **Greg** » Thu Nov 07, 2013 8:32 pm

Simple enough to join VE, Mike.

Graeme · Post by **Graeme** » Fri Nov 08, 2013 6:14 pm

I replaced the two variable resistors to no effect.

If i set the 2.2v to something like, but unstable, the TT works great and gets up to speed quickly but you can see the instability in the strobe so thats not good. I left it at a stable 1.46v, the TT takes longer to settle to speed but at least the speed is stable.

Not sure whats causing the unstable voltage, i guess i need to get serious with it and check all voltages, see if i can match the waveforms on the schematic with my scope and generaly poke about, see if i can find where abouts the voltage becomes unstable.

I dont know enough about this to understand why it only becomes unstable as you turn the voltage up. Would this suggest whatever is causing the instablility is after the variable resistor?

Greg · Post by **Greg** » Sun Nov 10, 2013 8:29 pm

Hi Graeme,

My advise would be to contact Dave Cawley of http://www.soundhifi.com on this. He is very approachable and I'm sure he will point you in the right direction.

Greg

Graeme · Post by **Graeme** » Sun Nov 10, 2013 10:42 pm

I will if i cant work it out with the scope.

On a seperate note, i chopped the plinth down today (god knows what that phenolic laminated ply is, but its bloody tough!) into a lightweight skeletal style and it seems to have improved its sound. Was a quick rough and ready experiment to see if mass reduction is the way forward or not. Seems it might be. My plans for a super lightweight, high stiffness plinth will now slowly start to be refined

audio-talk

technics sl150 issues

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