Warco WM180 problem

[GRIFFIN]

Hi All,

Hope I'm in the right place, it's my first post. I've got a Warco WM180 variable speed lathe and unfortunately after a year or so of very light use it has stopped working. I've traced the fault to the potentiometer (knob that changes the speed) but don't want to replace it with one from the makers, as it is Chinese electronics at their worst and the tiny little plastic lugs that keep the centre rotor in place will surely break off again. Does anyone know of a good supplier of potentiometers? short of any advice, I will call into RS components on Team Valley tomorrow to see what they have to offer.

Any help would be gratefully received.
Cheers, Griff.

[Lew_Merrick_PE]

Griff -- Knowing where you are in the world would make our advice more useful to you.

[awemawson]

Hi Griff, welcome to the forum. Can't help with the pot, but your mention of Team Valley suggests Gateshead to me?

If you edit your profile you can get your location to show under your users name in your posts. It's the entry called 'personal text'. The entry called 'location' doesn't show up unless someone goes into your profile to look at it.

[John Rudd]

Depending on which circuit board is used for speed control, the pot is a special.
They are a cimbined switch/ variable resistor. The switch contacts making it unique....closed when in the off position and open to run...if this is the case RS is no good nor is any other electronics supplier, ESR or Maplin.....oem part Im afraid....

So which board is present in your machine?
If an oem part is needed, I may have a spare....what is the value of yours ? 4.7k?


I'm coming to Gateshead on Friday and could bring it with me......if this helps

[GRIFFIN]

Hi and thanks for replies,

Sorry I thought my location was revealed in the header on my post, I'm in Consett in the north east of England.

Its Just a simple 3 terminal pot with the on off controlled separately by the main switch.

Hope attached photos will clarify.

Cheers, Griff.

[PK]

So the good news is: That is a very common, vanilla, part. RS carry them, http://www.maplin.co.uk/p/4k7-andohm-miniature-linear-single-gang-potentiometer-jm70m . No pun intended, but you may need to tweak your knob to suit the shaft....

[hopefuldave]

As has been said, standard part - you could use a higher-rated (e.g. 2watt) pot in its place, they tend to be longer-lived, more rugged, slightly more expensive...
While you have it open it's worth checking all the electrics, particularly eaarthing/insulation and the ratings on microswitches, and be aware that the speed pot isn't isolated from mains and can give a nasty belt or if the terminals touch earthed metal will kill the speed control pcb.... A plastic-bodied pot is the Chinese way to make it 'safe'! Use a plastic, not metal, knob and put an O-ring between knob and panel to exclude dwarf and fluids while you're at it.

Dave H. (the other one)

[GRIFFIN]

AAAAGH,

The bad news is, The ones at RS and Maplin are of carbon track type and as such they are rated at less than .5 watt. I bought one for a couple of quid to try but it didn't work. Incidentally, the motor turns when I connect the wires without the pot, so the fault is not in the circuit board or the motor its self.

The one I need is WX 14-12 wire wound and rated at 3 watts, 4k7 ohms +/- 5%

So if you have a spare John, or anyone else for that matter, it would be greatly appreciated.

Cheers, Griff.

[Sea.dog]

If you get stuck, there are several on eBay, all from China however, and rated at 5W.

[John Rudd]

It wont be a wirewound pot irrespective of the board.
I suspect you have a problem elsewhere...
Can you post up a photo of your board....please

[Sea.dog]

If you search for it online it comes up as a wirewound John

[GRIFFIN]

Hi John,

I've taken the back off the pot, you will see that it is wirewound and that one of the little plastic lugs, that hold the centre rota in place, has broken off. This has allowed the rota to come loose and fall out.

As requested I've also posted photos of the board as well as its label.

Cheers, Griff.

[GRIFFIN]

Try again, two attachments missing from last post!

Cheers.

[GRIFFIN]

Two attachments again missing from last post!

Cheers.

[GRIFFIN]

Still trying to post other two photos!!!!!

The website encountered an error while retrieving http://madmodder.net/index.php?action=post2;start=0;board=5. It may be down for maintenance or configured incorrectly.
Reload this web page
Press the reload button to resubmit the data needed to load the page.

Then when I reload I get this message!!!!!!!!!!! AAAGH

You already submitted this post! You might have accidentally double clicked or tried to refresh the page.

[awemawson]

That's a REAL quality pot - so how uneven the wire winding is on the track 


BTW 640 x 480 is a very convenient size to post pictures here and saves people who's screen isn't the size of a football stadium scrolling all over the place while still keeping very adequate resolution and saving space on the server.

[John Rudd]

Hmmm, Kbic controller...fairly reliable...

So what are the symptoms with the lathe that drew you to the pot being faulty?

Do you have a digital multimeter to fault find with?

[GRIFFIN]

Mmmmm, Yes I have a multi meter and the problem started quite a while ago with the lathe tripping the circuit breaker on the mains board but it only happened a handful of times and the problem stopped. Then a week or so ago the trip switch went off a couple of times when I turned the pot. After resetting the circuit breaker for the second time the lathe wouldn't work at all and the pot had fizzed a bit when it tripped out.

I checked everything with the tester and the only fault I could find was on the pot. Current was getting in but no matter where the knob was rotated there was nothing coming out! I then took the back off the pot to find one the tiny plastic lugs had broken off and the central rota had come off (with hindsight it must have been loose and occasionally touching the case causing it to trip out).

As I've mentioned in an earlier post, when I bypass the pot and connect the wires the lathe works but obviously only at one speed! This would indicate that everything else is working and reinforce the theory of the faulty pot.

I've located a couple of wirewound pots in china with the correct specifications and ordered them to try out my theory and I may try to bond the centre rota in place on its plastic carrier and rebuild the old pot as a temporary measure until the new ones arrive from china.

Oh and I take on board about the size of the jpeg, I wrongly assumed that there would be a built in device to limit the size on screen, I will make them smaller in future. I'm still new to the forum and will get better as time goes on. Of course you could left click on the attachment name, this will download the photo so you can view it in your computers photo viewer at the correct size for your own screen.

BTW John, is that a Chipmunk in your avatar?
 
Cheers, Griff.

[GRIFFIN]

Just an update,

I rebuilt the pot with a little hot melt glue replacing the tiny plastic lug & it now functions as it should, according to the multimeter. However, as someone previously forecast, the shorting out that was part of the original problem when the pot fell apart inside, has damaged the PCB or one of the components on the control board. When I re-connected the pot & wiring the lathe works but only at one speed the equivalent of about half the max rpm, regardless of where the pot is rotated to.

Looks like I'm gonna have to bite the bullet and buy a new pot and control board from the dealers! I assume it would be cost prohibitive to have it tested and repaired professionally, unless anyone else knows better?

I will wait till the new pot comes from China first though, just in case the problem is in the old repaired pot.

Cheers, Griff.

[John Rudd]

Griff,
I can repair your board if needed, or alternatively supply you with a good  tested second user one.
You need to bear in mind that where ever you source a replacement board from that:
1) you need to install the white resistor onto the replacement board( the big white resistor in the right) and
2) you will need to fine tune the board to your motor....the min/max speed accel, IR a d IC adjustments
I can give you a link to the instructions on how to do this or send a copy via email.

I'm goung to be back at Gateshead end of November, I could help sort out if you need any help...

[GRIFFIN]

Thanks for all your help with this John,

it's all fixed, up and running again & couldn't have done it without you.

As I said earlier I am very disappointed with the reliability of the Chinese electrics, the original pot just fell to bits inside! Real shame that something you can buy for less than five quid can do so much damage, rendering an entire machine inoperable.

Thanks again & good to meet you.
Cheers, Griff.

[John Rudd]

Original controller now repaired and on its way back to Griff...