Very Slow Sony PS-X4

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I have a Sony PS-X4 which is running way too slow.

I bought it knowing that it required to be repaired, however I was expecting something less severe, and possibly fixable by merely adjusting the speed clock on the underside of the plinth. I had done this before successfully on a PS-X6 which I still use daily.

However, I tried that and the speed didn’t come close. I resorted to some guesswork and I reckon that it is running at about 25rpm!

I just wondered if there might be an obvious fault somewhere. I was going to replace all the electrolytic capacitors. I have a set here ready to go.

If anyone has any ideas that are worth hearing then my ears are all open!

cheers
 
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If the unit has an unknown history then you have to assume that more than just the speed control has been twiddled.

You are going to need an calibrated oscilloscope to begin work on this as you will need to be able to calculate frequencies of various waveforms... or alternatively a scope and frequency counter.

First check as always is to confirm rails are clean. You also need to look at the divided down crystal oscillator frequencies and confirm they are correct. Also check the pickup is working and giving a clean signal in relation to rotational speed.

The biasing and offsets have a specific alignment procedure that must be followed.

It is possible the fault could be a dodgy hall sensor... again the scope is needed to look at the outputs of these.
 

PRR

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Basics.

Does it spin by hand freely? That type motor may have a "lumpy" feel from all the magnets, but should not drag like 40 year old fish-oil.

Raw DC power at C102 C103: + and - 24V or something less? Dried-out caps will give high ripple and low average voltage; the rest of the system will be upset.

If cleaning or recapping makes it run 40RPM, you *may* be able to fix that with a strobe disk and the most obvious trimmer. But of course if the previous user diddled all the pots, a full set-up may be required.
 
Hi Mooly, thanks for the advice. Out of my ability range I am afraid. No oscilloscope for starters.

I did check one of the test points which was meant to be 14V but actually read about 25V. There are quite a few variable pots underneath so I have no idea what anyone else may have done to them. I'll have to start somewhere. Anyway, if all else fails I will get my money back on parts.

As for the free rotation of the platter, I did wonder if it felt a little stiff. I'll compare it to my PS-X6.

Also, at first the platter was not stopping on completion of the record but I noticed that the reed switch was miles out so sorted that.

I do get the impression there are many things that need sorted. But generally looks OK. Nothing worn burnt or broken.

Thanks for now.
 
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From experience with vintage tables including Sony's, yes recap. Always. Even if they are not the cause i found recapping to help with speed control and locking. Table becomes much more responsive. Them caps are 40 yrs old... Start with ps caps.
 
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