Old Parvalux motor not starting properly

[Andrew SkinnerParticipant @andrewskinner94774]

That looks like a resistance split phase motor. Instead of the capacitor providing starting torque, the start winding is wound of much thinner wire. The altered reactance/resistance ratio (called ‘Q” factor) causes the phase shift for starting.

Isolate the motor wire pairs and measure resistance and check operation of the centrifugal switch.

[duncan webster 1Participant @duncanwebster1]

I once had a motor with the same symptoms. Turned out to be the springs on the centrifugal switch allowing the start winding to cut out before the motor was going fast enough. Slightly stronger springs cured it.

[Victor francisParticipant @victorfrancis52958]

Thanks to everyone for their suggestions. I have given it the sniff test as soon as things went south, couldn't smell anything.

I just need to get in the motor to have a look at its innards.

[Victor francisParticipant @victorfrancis52958]

Try as I might, the motor won't split. Maybe the shaft is deformed.

The starting and attempt to run is cyclical, the motor kicks in, fails to run and kicks in again. This happens every 5 seconds or so. It happened under load and with load removed. It basically does this as long as power is going through it on a continuous loop.

After reading about the centrifugal switch I thought that might be the issue, but would the motor start at all if that was the problem.

The connection "plate" is marked, start on the left wire and run on the two right ones.

Not been able to get into the motor is frustrating, with the bolts removed there is nothing else which would hold the parts together.

Looking at the protruding part of the spindle visible with the bearing cover removed, I can see some marring to its edge. Someone has obviously been there before and might have deformed it.

[Victor francisParticipant @victorfrancis52958]

The strangest part of it all is the lack of any information about old Parvalux motors online. There must have been enough people taking these things apart.

This happens more and more often with vintage turntables and tonearms, years ago there was a wealth of information online, now just a mass of commercial entities trying to flog something.

Is there a way to split to motor apart which is eluding me?

[Victor francisParticipant @victorfrancis52958]

Posted by duncan webster on 28/09/2023 11:54:06:

I once had a motor with the same symptoms. Turned out to be the springs on the centrifugal switch allowing the start winding to cut out before the motor was going fast enough. Slightly stronger springs cured it.

Thank for giving me hope, Duncan. The problem is now getting into it in order to check that switch.

[EmgeeParticipant @emgee]

Victor

I guess the Start and Run refer to winding ends so you should be getting the winding resistance if you measure between the end of each winding and the Neutral post with a multimeter.

If you don't have continuity on the Start point and N you will need to investigate further.

Emgee

[Victor francisParticipant @victorfrancis52958]

Posted by Phil Whitley on 28/09/2023 10:06:23:

there appears to be a centrifugal switch in your pic of the connection box, you need to check the contacts are clean and the switch is operating cdorrectly, it sounds from your description that the motor is trying to start, but the contacts, which are closed when the motor is stopped, are not making contact properly and are not allowing sufficient current to flow to the start winding. , Can you see and clean the contacts (with an emory nail board) without stripping the motor? If not you need to remove the rear cover from the motor, not the shaft end. are there three screws in the centre of the rear cover, near where the shaft would be? these are bearing retainers and need to be removed before the end cap will come off!

Phil

Phil, you are right, that is the centrifugal switch. Unfortunately the only visible part is its top. No contacts are visible.

[Victor francisParticipant @victorfrancis52958]

I am useless with a multi-meter but have a cheap one here. Not sure whether this means anything, there is continuity between the yellow run wire and the post where the brown start wire attaches with brown wire removed.

There is no continuity between the brown run wire and the start post, but there seem to be continuity between the brown run wire and the brown start wire. The continuity is intermittent and wiggling the brown run wire seems to affect it.

Still trying to split the b…. thing apart.

[MacolmParticipant @macolm]

It can be easy enough to bypass a centrifugal start switch. Assuming the terminals are accessible, it needs a momentary push to make mains capable switch connected across the start contacts. While the motor is powered and trying to start, press the switch for a couple of seconds. If it gets up to speed, it is bad contacts. If not, it is something else. Make sure to release promptly in either case.

I used to have an E Lutz (before ELU) sander with an induction motor, and a double toggle switch. One side was power to the run winding, the other was sping biased to off for the start winding. Simply press both to on, then release, leaving the motor running.

[Victor francisParticipant @victorfrancis52958]

The brown start wire, which showed intermittent continuity with the brown run wire, has come undone where it was spliced. I removed the heatshrink and it just came off. Maybe it was me messing around with it or maybe it just happened due to vibration and crap soldering.

Might have been the reason for the attempted starts, maybe it was not receiving constant power and kept going back to the start phase.

Biggest problem is that the wire is too short to allow for it to be spliced on again without taking the motor apart.

[Victor francisParticipant @victorfrancis52958]

Posted by Macolm on 28/09/2023 15:18:30:

It can be easy enough to bypass a centrifugal start switch. Assuming the terminals are accessible, it needs a momentary push to make mains capable switch connected across the start contacts. While the motor is powered and trying to start, press the switch for a couple of seconds. If it gets up to speed, it is bad contacts. If not, it is something else. Make sure to release promptly in either case.

I used to have an E Lutz (before ELU) sander with an induction motor, and a double toggle switch. One side was power to the run winding, the other was sping biased to off for the start winding. Simply press both to on, then release, leaving the motor running.

The start wire is too short, nothing can be done without the motor splitting apart. So far the gap between parts is around 5mm, no amount of tapping ( quite forcefully) around the edge of either shell increases the gap.

It's turned into a mechanical puzzle.

[SillyOldDufferModerator @sillyoldduffer]

Hate to recommend anything without seeing the motor, but my guess is the housing and shaft are held firmly together by the bearing: These are often a tough press-fit onto both shaft and housing.

I'd make or perhaps buy something like a harmonic balance puller, the example below being about £15 from Machine Mart:

The bolts go through the spider into the 4 holes in the motor case near the bearing. Then the black bolt is tightened against the end of the shaft. Tightening puts an enormous pull on the housing and it and/or the bearing should shift.

I take no responsibility if the motor breaks! As this is tough love the bearing may have to be replaced. A press or large dead-blow hammer may be needed to refit it.

Might be cheaper and easier just to replace the motor. Symptoms suggest the centrifugal switch is malfunctioning, which could be anything between an easy fix or a hopeless search for an unobtainium spare part/ At minimum I'd assume it will cost new bearings.

Dave

[Victor francisParticipant @victorfrancis52958]

Dave, thank you.

I did think the bearings were holding everything together and planned a visit to a local mechanic for a puller.

The issue now seems to be the two run wires, looks like they have come apart where spiced together. It's either happened due to me messing around with the casing or that was the original issue causing an intermittent contact.

The bearings are probably pressed on hard to begin with and got tighter when the last owner attempted to hammer the spindle deforming it in the process.

When I first bought the lathe I intended replacing the motor's bearings, I gave up when I realized the interference fit was too tight for the tools I have.

[Victor francisParticipant @victorfrancis52958]

Seeing as the wires are too short, and the casing won't budge, I wonder whether some sort of mini wire connector could be used.

Soldering another wire to what is left visible would be impossible, but the connectors I am looking at seem to have a mechanical connection not needing soldering.

[noel shelleyParticipant @noelshelley55608]

Hey Vic If your near me or going to the MMEX I may be able to help As Dave has said the gear pulling tools may be needed I also have the test gear. Noel.

[Victor francisParticipant @victorfrancis52958]

Posted by noel shelley on 28/09/2023 21:23:51:

Hey Vic If your near me or going to the MMEX I may be able to help As Dave has said the gear pulling tools may be needed I also have the test gear. Noel.

Noel, that's very kind of you. I would love to come to the MMEX but unfortunately can't.

I am in London, actually close to Alexandra Palace. Shame I never visited when it was on there as I understand it won't return.

The bearings in the motor are fairly okay, but noisy enough to be replaced. It would be ideal to sort the lot out in one go.

Next week I am picking up an Unimat SL, hopefully it is complete enough to be used straight away and I can resume making turntable parts.

Again, thank you.

Victor.

[Phil WhitleyParticipant @philwhitley94135]

mark all the wires and remove them from the connection plate, remove the two screws from the top of the connection plate and the centrifugal switch may just lift out of the motor, and be able to be examined and cleaned without having to strip the motor!

Phil

Edited By Phil Whitley on 29/09/2023 16:11:24

[Victor francisParticipant @victorfrancis52958]

Posted by Phil Whitley on 29/09/2023 16:10:22:

mark all the wires and remove them from the connection plate, remove the two screws from the top of the connection plate and the centrifugal switch may just lift out of the motor, and be able to be examined and cleaned without having to strip the motor!

Phil

Edited By Phil Whitley on 29/09/2023 16:11:24

Ohil, thanks for the suggestion.

I have removed all screws, but thought the centrifugal switch could not be removed unless the motor was split. I will have a look at it again.

To be honest that switch covers up the remaining bits of wire, with it removed it would be much easier to splice or add connectors to whatever wire is left.

When the coil wires were extended copious amounts of solder was used, this made the connection brittle and so the wire just broke. The same issue is on all the three wires,

[Victor francisParticipant @victorfrancis52958]

Phil, just gave it another go, the centrifugal switch is not coming out. It appears to be slipped over the end of the spindle.

The only option is some fiddly messing around to use small connectors in order to extend the wires which have broken off.

I am hoping the broken wire was the cause of the centrifugal switch not working properly, either that or there is something wrong with it and I broke the wire after the issue.

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