Author Topic: Turntable problem questions  (Read 916 times)

Offline 1200GXman

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Turntable problem questions
« on: March 14, 2017, 07:48:24 AM »
Hi Guys
Just need some advice. My father's Kenwood turntable is having the following symptoms. When he sometimes switches it on to play, it doesn't start.
I inspected it and removed the platter and the belt to check motor. When switching on, the motor either stands still giving resistance when I try and turn it by hand. Eventually when I try a little force to "kick-start" it, it would start to turn. Another time, the motor's "head" just vibrated slightly and I again "kick-started" it by hand to test.
He also complained that when it eventually works, it would either loose speed or come to a stop when he is busy with his second LP.

A good friend suggested I replace the cap on the system. I could find the following cap: 103P 2KV Murata 50.
Can this cap cause the symptoms or is there something wrong with the motor?
I stripped and cleaned everything. The platter shaft was still having enough watery oil from a previous service.
The motor I also partially stripped and it also was still fine on the lubrication side of things.
I played safe and cleaned everything and re oiled using hair clipper oil.
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Offline chrisc

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Re: Turntable problem questions
« Reply #1 on: March 14, 2017, 07:53:37 AM »
An AC motor needs a capacitor in order to start

Offline 1200GXman

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Re: Turntable problem questions
« Reply #2 on: March 14, 2017, 07:55:55 AM »
Yes, that is how I understand it. I am just trying to figure out if I am looking at the right part and on the right track problem solving. Just concerned something serious is wrong since its a 70s turntable. Especially because it either looses speed or completely stop after working for a while. Can the cap cause this as well?
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Offline chrisc

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Re: Turntable problem questions
« Reply #3 on: March 14, 2017, 07:57:52 AM »
To get a 100% accurate opinion, send a message to Jacques (alternative route).  He runs a turntable repair shop in Mowbray, Cape Town and is the guru on turntable problems

Offline Shonver

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Re: Turntable problem questions
« Reply #4 on: March 14, 2017, 08:02:56 AM »
If the motor is the mains-powered type, a safe assumption is that the cap needs replacement. They're not expensive, either.
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Offline fdlsys

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Re: Turntable problem questions
« Reply #5 on: March 14, 2017, 08:04:16 AM »
If it's a universal 110/220v AC motor (almost always was in the 70s), then cap is always the first point of failure. Such motor has two coils and when they are running on 220v they need a cap between them to provide the phase shift (delay). Angle of phase shift is dependent on the cap value and is important for optimal motor function.
Fresh good quality polyester cap never hurts. 2kv is excessive; 1kv is more than enough.
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Offline Shonver

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Re: Turntable problem questions
« Reply #6 on: March 14, 2017, 08:12:39 AM »
I believe the "103" means 10nF, which seems a bit small for a motor start cap. Capacitance for this application is usually 10x higher or thereabouts, so you may be seeing the suppression cap that goes across the switch.. Is there one mounted directly on the motor (this is the usual place)?
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Offline 1200GXman

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Re: Turntable problem questions
« Reply #7 on: March 14, 2017, 08:15:02 AM »
No cap over the motor.Wires coming from the small circuit board containing this cap and some other things going to switch and motor. Even over switch there is no caps like my amps.
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Offline marantz123

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Re: Turntable problem questions
« Reply #8 on: March 14, 2017, 05:53:48 PM »
There should be just one capacitor across the micro switch and im using a 68nF 400v x2-type as a contact debounce cap with no issues. 33nF or 47nF may work fine as well. What is concerning..if not the cap, then test the windings on that motor..there may be a breakdown in insulation resistance with increase in temperature. Test resistance of each winding when cold, then again once the problem starts..disconnected ofcourse. Good thing with having 2 windings, makes comparisons easier. Did these checks on a Pioneer PL25 as advised by one of the experts here. Good luck Sir.

Offline JonnyP

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Re: Turntable problem questions
« Reply #9 on: March 14, 2017, 06:03:09 PM »
Sounds like the cap as others have said.  One of my Thorens TTs ocxasionally starts backwards.  A web search suggests it's the cap. Once it starts the right way it is great though
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Offline 1200GXman

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Re: Turntable problem questions
« Reply #10 on: March 15, 2017, 09:24:27 AM »
@marantz123
Why would a motor all of a sudden start to give such problems? Just curious because previous owner was a vinyl guy and used it many nights for hours on end without issues that I know of.
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Offline Kent Kassler

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Re: Turntable problem questions
« Reply #11 on: March 18, 2017, 04:47:51 PM »
Lubrication....does the motor not just need a drop or two?
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Offline ghostinthemachine

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Re: Turntable problem questions
« Reply #12 on: March 18, 2017, 11:25:51 PM »
That's a shaded pole motor and does not need a start capacitor. The small capacitor on the PCB is a spark arrestor for the switch. The motor needs to be oiled.
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Offline Kent Kassler

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Re: Turntable problem questions
« Reply #13 on: March 19, 2017, 07:45:31 AM »
I have a Kenwood here which had the same problems....top plate on the motor mount has two small holes and an "OIL" label and Yip it now runs just great now this one does...
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Offline 1200GXman

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Re: Turntable problem questions
« Reply #14 on: March 22, 2017, 02:10:07 PM »
I test played 3 lps this past weekend and no issues with starting and stopping  :nfi:
They were played one after the other to try and build up heat into the motor,etc
So I think I will inspect again this weekend to check for oiling hole.

Couple of weeks ago to try and clear the problem I did the following:
I checked the platter shaft. I think was serviced by previous owner as it was oiled. I cleaned it anyway and oiled again.
The motor was also semi dismantled and looked oiled. Cleaned and re oiled shaft.
Sansui AU-101, Sansui AU3900, Rotel RA935BX, Pioneer SA-6500 Mkii, Marantz PM53, DIY kit amplifier