Sony PS-X45 "problem"

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artemusprime
Posts: 4
Joined: 06 Oct 2016 23:04

Sony PS-X45 "problem"

Post by artemusprime » 22 Apr 2018 20:11

Hi, I have a Sony PS-X45 with a strange issue.
After about half an hour of playing a record, the green quartz lock light starts flickering and becomes dim shortly after. The speed is unaffected, so it's not a big deal. At first I thought that it could be the light itself but if I switch to 45 RPM, the light is back and doesn't flicker. I've already readjusted the speed detecting head under the platter, because I was getting strange noises and light flickering only at 33 RPM (the head was to far from the platter). I reckon the problem is somewhere in the path of the signal from the quartz crystal to the light itself (and not the motor), but can't figure it out from the service manual. If anyone knows a fix for this it would be greatly appreciated. The turntable works flawlessly otherwise.

langer

Re: Sony PS-X45 "problem"

Post by langer » 23 Apr 2018 22:17

Hello,

the two LED for the 33 and 45 turn display is only controlled by a switch (not directly by electronic).
This switch consists of two parts. The one switch part is only responsible for the control electronics of the plate motor, the other switch part changes only positive supply (anode) for the two LEDs 33 or 45 turns.
If the led flickers for 33 turn or goes off, the led switch will switch for 45 turn but working it may just be a contact problem of this switch.
Since such a defect of the semiconductor led is very unlikely, it is much more likely that the contacts of this switch should be cleaned.

Greetings langer

artemusprime
Posts: 4
Joined: 06 Oct 2016 23:04

Re: Sony PS-X45 "problem"

Post by artemusprime » 24 Apr 2018 01:29

Hi,

Thanks for your reply. The LED is not the problem, I meant the green quartz lock lamp becomes dim. It only happens on 33 RPM after half an hour, but the speed is fine. Must be a component somewhere that's failing.

langer

Re: Sony PS-X45 "problem"

Post by langer » 24 Apr 2018 08:26

Then I misunderstood because in the schematic there are except the three led (33, 45, repeat) only a lamp that looked like a power indicator for me.

This lamp (its positive side) is supplied (after rectifier) by Q108 (this regulated by a zener diode D105) with 7.5 V regulated.
You would have to measure this voltage, whether it corresponds to about 7.5 V and whether this voltage breaks when the time is over.
It comes mainly this zener diode in question and a electrolytic capacitor (C183) which could be bad.

Greetings langer

artemusprime
Posts: 4
Joined: 06 Oct 2016 23:04

Re: Sony PS-X45 "problem"

Post by artemusprime » 24 Apr 2018 16:44

Ok, I'll have look at that. Can zener diodes go bad? Also, what about C155 (220, 6.3v) capacitor? I'm not sure what it does in the circuit.

Thanks.

langer

Re: Sony PS-X45 "problem"

Post by langer » 24 Apr 2018 21:43

Zener diodes do not get bad in the sense that an electrolytic capacitor loses capacity, for example, but they can suffer a defect, especially a temperature-dependent defect.

C155 would be on the negative driving side and a loss of capacity at the Q156 base would not be associated with this symptom
but if you open it you can also measure it like Q108, Q156.

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