speed control pcb for Clarke CL300 lathe

[Rik ShawParticipant @rikshaw]

Felix – Over to John Rudd as regards advice – John really knows his onions!!!

[Felix CantesanuParticipant @felixcantesanu73894]

Thank you for your input, John and Rik.
Here are a couple of shots of the board. You can see on the back where there was a burn and circuit was interrupted, fixed it by soldering a thin copper wire (is this OK?).
Looks like I have to upload a photo to another site and point to there from here? Can't seem to be able to upload the pohoto directly here…the board is the FC250J/110V

A local helper is saying that it may be that the bridge rectifier shorted, taking out the trace, then bridge rectifier went open. Can test with diode meter. The FETs on the heatsink, can we get a good look at those too? That is what actually drives the motors.
Sounds about right to me…now to figure out exactly what he wants to be able to help further…
ANy advice you guys have will be appreciated!

[John RuddParticipant @johnrudd16576]

Felix,

The fets are IRFP450 from memory, can go short circuit drain-source, usually causing the motor to run at full speed.

They can take out the opto isolators too….Use your dvm to check the bridge rectifier…

After repairing the board, test with a 100watt lamp in place of the motor first…..

[Felix CantesanuParticipant @felixcantesanu73894]

Yes, the fets are IRFP450. When the burn-out happened the motor did seem to come on at full speed.
I checked the bridge rectifier (got directions online on doing this) and it reads 594, which seems to be OK from what I understand?
I have repaired the burned section on the board using thin copper wire (got covered with solder but it looks like it's got a good continuous connection now.

Do you think it's the FETs that might be shorted out? Perhaps this is why my fuse gets blown as soon as I plug the lathe in to power?
Seems as I am chasing a demon that might not be found here…, at least not by me. Perhaps best option is to buy a new board? Or new lathe altogether? I wish I knew what I was doing…

[Bob DringParticipant @bobdring71940]

Hi Felix,

The main problem when beginners troubleshoot electronic stuff is the foreknowledge and test equipment that you need to do it. For a one off repair this is just not cost effective, unless you are going to take up electronics as a hobby as well.

My suggestion would be to try and find one of those old fashioned TV/PC repairer shops and having attached a light bulb instead of the motor have them look at it. Finding a circuit diagram to put with it might save you money.

OK, so if you want some tips to try anyway…

Remove parts, one by one, from the PCB and then test them with a DMM, as often the circuitry and other failed parts can make good parts look bad.

In your case where you have a fuse blowing. Remove the MOSFETs and test them, also see if it still blows the fuse with them removed. The idea of connecting a lamp as a load while testing is really good. If you suspect the bridge rectifier remove it as was done with the MOSFETs and see if the fuse still blows, etc.

Don't forget that circuits like that you are troubleshooting are are often at mains voltages and have risks to your health…

Bob

[Felix CantesanuParticipant @felixcantesanu73894]

Posted by Bob Dring on 25/05/2018 20:57:42:

Hi Felix,

The main problem when beginners troubleshoot electronic stuff is the foreknowledge and test equipment that you need to do it. For a one off repair this is just not cost effective, unless you are going to take up electronics as a hobby as well.

My suggestion would be to try and find one of those old fashioned TV/PC repairer shops and having attached a light bulb instead of the motor have them look at it. Finding a circuit diagram to put with it might save you money.

OK, so if you want some tips to try anyway…

Remove parts, one by one, from the PCB and then test them with a DMM, as often the circuitry and other failed parts can make good parts look bad.

In your case where you have a fuse blowing. Remove the MOSFETs and test them, also see if it still blows the fuse with them removed. The idea of connecting a lamp as a load while testing is really good. If you suspect the bridge rectifier remove it as was done with the MOSFETs and see if the fuse still blows, etc.

Don't forget that circuits like that you are troubleshooting are are often at mains voltages and have risks to your health…

Bob

Thank you, Bob. I completely agree! I definitely have too many hobbies now to add electronics, and there is not very much interest either, however I thought I might get lucky and get to the end of this one problem easily

I'll look for a place that doesn't charge an arm and a leg, the one place I bought my new switch from wanted $110/hour…a
I did remove the bridge rectifier and it tests fine (followed directions online and from the DMM manual).
I'll take off the MOSFETs and test them (don't know how but I'll look that up). Perhaps this will do the trick for me…
Is there a place wher I can just buy the PCB with everything and just plug it in? Bad idea? It would be cheaper than buying a whole new lathe…

[Bob DringParticipant @bobdring71940]

Felix,

Me being in another country make any recommendations for a replacement PCB difficult.

Hopefully someone will step in with a solution for you.

Before getting a replacement PCB you really need to be 100% sure the motor is good or you might end up in a catch 22 situation by blowing the new PCB. Have you contacted the seller? Are they near enough to you that you can take the motor and PCB to them for repair/replacement/testing? They would have a harder time justifying charging a lot for the fix than an independent repair company could.

Back to the tips.

Bridge rectifiers have been known to check OK on a DMM but break down on high voltages. Also is the 594 you mention, is it the 0.594 Volts forward voltage for each of the four diodes? if so, it sounds OK. What was the reverse voltage? Please can you post the link to the test procedure you used?

There is probably at least one high voltage capacitor that needs to be tested for a short too.

If you can get a circuit diagram I might be able to talk you through the troubleshooting…

Bob

[John RuddParticipant @johnrudd16576]

If you go to the first page of this thread, John Swift drew out the partial schematic, showing the bridge rectifier and fets and how the motor is powered…..there is sufficient information there to determine the cause of fuse blowing if it is confined to the board. This does not rule out any externally connected items such as the mains filter….

I suggest you disconnect the supply wiring to the board and check if there is a short circuit across the wiring as a first to eliminate the above, then procede with checks on the board….

Here is a link to how a typical machine is wired up, you may need to select an appropriate drawing as they are not all the same, but principally shows how the 110v ac gets to the control board.

https://littlemachineshop.com/info/business_resources.php?ID=1876291636&CAT=1

Edited By John Rudd on 26/05/2018 09:24:21

[Andrew FarrowParticipant @andrewfarrow93608]

Quite clearly this problem is going to run and run, however I have a very cheap and simple solution. For a year now I have been running my lathe on a variable speed controller available on eBay (see my original post 11/08/2017). It has so far been totally hassle free. You will need basic electrical knowledge to do the mod. The speed controller is still available, search;

220V AC Speed Control Controller For 400W Motor Output DC 0-220V

Give it a go, it worked for me and no I don't have shares in the company.

[John RuddParticipant @johnrudd16576]

Your suggestion may work if Felix has 220vac adjacent to his machine.

However, this item, 263084948505 would be better suited..

Edited By John Rudd on 26/05/2018 12:42:58

[Felix CantesanuParticipant @felixcantesanu73894]

Thank you all for your help!

I removed the bridge rectifier, went back online to get a clear example of how to properly test it, and it turns out that it is definitely a bad one. The fuse now doesn't get blown when I plug it in to power. Switch seems to work, it all sounds the same as before when I turn it to Forward or Reverse (as it engages something, there is the click). Should the motor engage when the switch is on and I turn the potentiometer to on and up? It doesn't for now…but honestly I'm happy to hear it do something and not just blow up the fuse
I'll replace it and report back with results.
Thank you again,
Felix.

[SillyOldDufferModerator @sillyoldduffer]

Hi Felix, how much spare time do you have? I have test equipment, soldering gear and a fair understanding of electronics and I wouldn't waste much effort on an old board. Briefly:

1. Test the motor with a battery to prove that it isn't causing the problem. If the motor is faulty, you're wasting your time looking at the electronics. You have to replace the motor first.
2. Using what skills and equipment I have, I'd run a few simple tests on the board. Chief suspects are the bridge rectifier and MOSFETS, then the electrolytic capacitors. With luck, I might find a quick easy fix.
3. BUT! When a board fails with blown fuses and burned out tracks, it's fairly likely that you'll find a trail of destruction such that several components have to be replaced. It's not unusual to end up fighting the board, fixing one thing only to find yet another problem. You have to ask whether the effort is worth it and recognise when you are flogging a dead horse.
4. The quickest way to fix the board is to buy a new one. That's probably also cheaper than paying someone to fix it for you. (Labour is so expensive, most modern electronics is fixed by swapping boards, not by diagnosing what broke.)

You might do better with Andrew Farrow's suggestion. – it's probably what I'd do even though I have a room full of electronic test gear. If the fault's not obvious move straight to an easier solution. Unless you enjoy learning new skills that is!

Dave

[Neil WyattModerator @neilwyatt]

Just a quicky – you can test the motor with a car battery, it won't run fast, but if it turns smoothly at as modest speed it is probably OK. If its needs help to get running in some positions or runs unevenly, it probably has duff windings or dodgy brushes.

[Felix CantesanuParticipant @felixcantesanu73894]

First of all: thank you all for your help! Especially Bob.
I am happy to report that my old trusty mini lathe is now back in business It was the faulty bridge rectifier. Swapped it out and it's all good. I didn't actually think it was going to be fixed and held my breath while plugging it in…but it's same as before, working properly and now with a shiny new main switch.
I am hoping I won't need to look for support with it for another 10 years of great service but I am grateful to have gotten the support form you guys.
All the best, Felix.

[Dirk KroschinskiParticipant @dirkkroschinski21703]

Thank you helping me reparing the PCB of my lathe.

My little machine is yellow, and sold under WEMAS brand, It is from 1992 .1995, so maybe one of the first versions

I inherited this lathe frm my father 1999 and used it until last year, just had to replace the belt five years ago

As many of you, I had the "ratteling" problem, and now I found you

My PCB is quite old, and I was looking for a condensator close to the relais and witth two diods nearby and foud something . I replaced "C1" , 110 uF the machine was working again!

Thank you for support

Dirk

[Neil WyattModerator @neilwyatt]

Posted by Dirk Kroschinski on 29/11/2019 17:23:23:

Thank you helping me reparing the PCB of my lathe.

My little machine is yellow, and sold under WEMAS brand, It is from 1992 .1995, so maybe one of the first versions

I inherited this lathe frm my father 1999 and used it until last year, just had to replace the belt five years ago

As many of you, I had the "ratteling" problem, and now I found you

My PCB is quite old, and I was looking for a condensator close to the relais and witth two diods nearby and foud something . I replaced "C1" , 110 uF the machine was working again!

Thank you for support

Dirk

That's good news, Dirk.

Neil

[Tim Hall 1Participant @timhall1]

Hi, I’m trying to repair my dads Metalworker lathe. It’s got a FC250J board in it.

The motor was running at full speed so after reading through this discussion I replaced the fets with two new

STW 20NK50Z.

Unfortunately now nothing works however I do now get a ‘buzz’ when the potentiometer is switch off?… it stops when I wind the speed up….any thoughts anyone?

many thanks
Tim

[David VarleyParticipant @davidvarley54927]

Hi, I have exactly the same problem. I bought a second hand CL300M. I also get a buzz when the potentiometer is in the off position and nothing when I turn it clockwise. When I move it anti-clockwise to the off position, the chuck give a wobble and it starts to buzz. It is like it is all back to front. Please can somebody help.

[Anthony KnightsParticipant @anthonyknights16741]

When the potentiometer is in the OFF position, the switch at the back is supposed to operate the interlock relays, which are there to ensure you start the motor from zero speed. The buzzing noise suggest to me that the relays are not operating, hence no supply to the motor. There is a diagram by John Swift, of the relay arrangement in the 4th post at the beginning of this thread.( between terminals 4 and 6). The diode could be faulty or resistors may have changed value. Electrolytic capacitors also deteriorate with age. Good luck.

Anthony

[David VarleyParticipant @davidvarley54927]

Thank you for your prompt reply. I will have a look at that.

[David VarleyParticipant @davidvarley54927]

Not had much time to look at the lathe, but I just turned it on and it was buzzing as before. I then moved the dial to the point where it just clicks on and the chuck started to move. I kept moving the dial on and off several times and eventually the lathe started to turn properly. It responded to the speed control and I could switch it off without it buzzing. Left it a few minutes, then did the same again, and it behaved the same, but did start to spin normally. I am guessing that perhaps the rotary switch may be the problem. I think I will order a new switch and try it.

[SillyOldDufferModerator @sillyoldduffer]

Posted by David Varley on 04/04/2022 16:01:06:

… I kept moving the dial on and off several times and eventually the lathe started to turn properly. I…

Sounds like a dirty speed control potentiometer.

Turning the knob moves a wiper arm over a semi-circular carbon track. The wiper is prone the pick up dirt and/or to damage the carbon track.

Worth giving the potentiometer a blast of Servisol Switch Cleaner No need to remove the cover, there are usually gaps the spray can be directed into under the terminal lugs and elsewhere.

Switch/potentiometers are easy to source is a replacement is needed, and straightforward to change with a soldering iron.

Dave

[Grindstone CowboyParticipant @grindstonecowboy]

Servisol is good, but last time I had a dirty potentiometer I'd run out, so tried Ballistol instead. Worked a treat.

Rob

[David VarleyParticipant @davidvarley54927]

Changed the potentiometer and the fuse holder which was broken and the lathe now works as it should. Although it still buzzes when I first turn it on, but now it buzzes when I turn the pot on rather than off, but it soon stops buzzing once it is on for a little time. Thanks for your help guys, very useful.

[Howard LewisParticipant @howardlewis46836]

If anyone else has a major problem, the CL300 is made by Sieg, who also supply the machine to Chester and Arc Euro, in different colour schemes.

Spare boards for S2 and S3 lathes are, or were, available from Arc Euro.

A poster on here, John Rudd (Hope he doesn't mind me posting this ) is very knowledgeable on these boards, and repaired one for a friend.

Howard

[Author]

Posts