Variable speed controller on a Hegner multicut 2S

[raythompson102]

Hi, I just bought a second hand Hegner scroll saw for spares /repair. The problem is the motor will not run, apart from that the scroll saw is like new. I’m fairly convinced the problem is with the controller. My questions are:
1) can the controller be repaired?
2) can Hegner uk supply the parts?
3) what is likely to be the problem?

 

[clogs]

I'd be wiring it direct to make sure it runs....by-pass the controller.....
then look for a speed controller from ebay....
Hegner spares are often well over price...

 

[raythompson102]

I looked up Hegner uk for a price on a new motor and it is approx £500, that’s why I thought about a repair instead, because I’m sure the motor itself is fine. I’m not really electrically minded so don’t know how to wire the motor directly. There are four wires coming from the motor red, black, white, and green. The red wire connects to a capacitor on the negative side, which leaves a positive lead from the capacitor.

 

[Myfordman]

If there is one thing worse than trying to make a repair it is when someone else has had a go and potentially moved wiring and destroyed evidence and clues as to the source of the problem.
As you are talking about positives and negative connections in an AC system which is meaninless, you should honestly leave well alone and seek expert face to face help.
Reading around, problems seem to be with open circuit potentiometers and failed thyristors/triacs on these Hegners. Woodworking machines often have problems with dust ingress and safety interlocks. I don't know if Hegner fit interlocks.
Hegner do not provide circuit diagrams or spares down to component level and work on an "open your wallet and they will help themselves" business model.
You are too far from me (southampton) and I have a months work ahead of me anyway but if you continue to be stuck, you could post the motor and controller still wired together and (not after others have had a go please) and I'll take a look. I usually have a good success rate and charge by the bottle of decent Red depending on complexity. No win No fee!

 

[raythompson102]

I have had a look under the cover. As I took the top off two small wires came off two posts on the PCB, they are too short to be able to move the top without them coming adrift. They come from the back of the motor and I think they are for feeding back the speed of the motor to the controller. On utube there is a guy who had a similar problem and said it was the capacitor so I have ordered one but I have now checked the capacitor and it is OK, so that is not the problem. I’ve also checked the on / off switch and that is OK, so the problem must be one or more of the components somewhere on the PCB. You’re right in your assumption that I am not an electrical engineer but I do like to fix things myself, especially if it is something either obvious or fairly simple.
I read on some ones else's conversation that they were able to buy a new PCB for the controller, so I think that will do the job. I’ve contacted Hegner and am awaiting a response. Additionally they now do a new foot controller which incorporates the speed control, rather like a sewing machine pedal, and it can be retrofitted to existing machines so I am also waiting on a price for that.
you are a fair distance from me but not too far if all else fails. Would you need the whole motor or just the PCB?
thanks for you help so far.

 

[Johnwa]

I'm sorry if this response upsets people but I really do worry about the questions and statements made by the amateur electricians on this forum. If you do not KNOW what you are doing then for gods sake don't mess, you will hurt yourself and maybe others with your "repairs", 240 volts makes a hell of a bang and it reall bloody hurts when you get a good pisser(sparks will know what I mean) and it will cost a fortune to repair! Please leave it to a qualified tradesman, it may cost but it will be safer in the long run and as an added bonus you get to stay all in one piece. Rant over☺

 

[Myfordman]

Spot on Johnwa
Add to that people who don’t read replies fully and then ask questions already covered.
I used to get a lot of stick for my replies along the lines of “if you have to ask then you should not be doing this” and hanged to offer some suggestions of help but that has its difficulties too. I’m tempted to give up.

 

[AES]

It MAY be worth your while to send a PM to member scrimper (or wait for him to stop by this thread). He obviously knows a lot about Hegners, AND he used to own/run his own electrical appliances repair shop.

BUT +1 for the comments above, do NOT try it yourself unless you know what you're doing.

And with the greatest respect, if you refer to wires on any AC unit as + and - then you clearly don't understand the "electrickery" in that case!

Like you I do like to repair stuff, myself, but one of the biggest "skills" in that game is to KNOW when it's time to call in a - ideally - face-to-face expert.

But from the above, it looks like you've already started?

Only trying to help, 'onest mate.

 

[Johnwa]

Thanks for your support Myfordman, I don't think that some people realize just what damage they can do messing about with electrics particularly 240v . I personally make it a policy not to respond to some of the more naive questions asked. I don't want the responsibility when an armchair spark blowing the end of his finger off because he didn't understand what I had written. I feel that the more electrically experienced members should think twice before responding to some questions asked, not out of spite but out of safety concerns for other forum members

 

[MorrisWoodman12]

I have repaired a couple of lathe speed controllers and was a little surprised when I investigated the first to find it was a 240V DC motor. So I agree with the sentiment that if you don't know what you are doing you may make it an awful lot worse. And worse it can be downright dangerous to life, limb and property.
I can't workout if you're Barnham near Thetford or near Bognor Regis. BG is not so far from Uckfield (or Portsmouth and @Myfordman ) and my daughter is close to Bury St Edmunds so near Thetford and we see each other every few weeks.
Do I know what I'm doing? Well I mucked around designing electronics for 50 years and companies actually were keen to pay me for my efforts. Let me know if I can be of help. (rates very similar to Myfordman's)
Martin

 

[raythompson102]

First of all, thanks for all the comments so far, good and bad. I am only trying to do a easy fix within my own limitations, and I have just about reached those. I consider changing a capacitor on a motor or an on / off switch within my capabilities. I am in my 70’s now and survived so far, so I do work in a safe manner, for instance always unplugged and any capacitors discharged, and I always photograph every stage so I can put it back together again. When I said + and - for the wires, I should have said brown and blue, (I have a boat which I rewired and that is all DC).

 

[Spectric]

by the amateur electricians

Is there such a thing, you are either an electrical engineer or someone taking a chance. I suppose the nearest we have to an amateur is the so called domestic installer, knows just enough to wire a house on a good day.

 

[raythompson102]

It MAY be worth your while to send a PM to member scrimper (or wait for him to stop by this thread). He obviously knows a lot about Hegners, AND he used to own/run his own electrical appliances repair shop.

BUT +1 for the comments above, do NOT try it yourself unless you know what you're doing.

And with the greatest respect, if you refer to wires on any AC unit as + and - then you clearly don't understand the "electrickery" in that case!

Like you I do like to repair stuff, myself, but one of the biggest "skills" in that game is to KNOW when it's time to call in a - ideally - face-to-face expert.

But from the above, it looks like you've already started?

Only trying to help, 'onest mate.

Thanks for constructive reply.

 

[Myfordman]

I'm becoming intrigued by this controller. Looking at photos the motor appears to be fairly standard looking TEFC induction motor body complete with a chunky capacitor on the side. I presume it must be permanently connected with no centrifugal switch to allow it to be variable speed. These machines are too old a design to have any sort of variable frequency drive and in any case would not need a capacitor.
So I can only assume they are controlling the supply voltage with a thyristor and relying on electrical slip in the motor to regulate the speed, maybe as suggested with some tacho feedback although such a motor would not normally have room for a tacho generator.
Usually the thyristor approach is used with universal brush motors but I see no evidence of brushes and again there would be no need of a capacitor.
If it is a special motor, then maybe it explains the exorbitant price of a new replacement.
All very curious.
I'm almost tempted to pick up one on ebay but even dead ones I've looked at go for silly money.

 

[raythompson102]

Please find attached a photo of the inside of the speed controller. The blue and brown wires on the rhs are from the capacitor. The mains lead wires are connected via spade terminal at the bottom of the photo to the PCB, and the on/off switch is at the top. I have a multimeter and tested the capacitor and it reads a steady 8uF. And I’ve also tested the on/off switch for continuity when switched on and off and it is also working correctly. This is far as can go apart from changing the PCB if required. I can take a picture of the motor plate tomorrow and post that if helps? I understand it is an induction motor and has what I believe is a Hall effect sensor at the back of the motor cover to sense the motor speed. It is these wires that are too short and come off as soon as the cover is removed from the motor, these attach to two posts at the top of the PCB next to the brown wire from the capacitor.

 

[Myfordman]

I've found out a bit more. An integrated circuit U211B datasheet is used with a triac and the speed sensor to control the motor.
Quite a sophisticated approach. If the triac has failed that should be easy enough to change.

 

[OCtoolguy]

I'm following this thread as I have a Hegner also. I'm in the U.S. where we are on 110 a.c. I'm probably the type of person some of your answers are aimed at but I do enjoy reading and eventually hope to see the solution. I have just enough knowledge to get myself into trouble so I will just read along and hope that if this ever happens to my saw, I will be able to find some nearby to get me back up and running again. I feel that Hegner stuff is vastly overpriced so if there is a way to fix anything without paying them their "ransom" I'd prefer to do so.

 

[raythompson102]

Following from yesterday, also attached is the photo of the motor specification plate.

 

[raythompson102]

I'm following this thread as I have a Hegner also. I'm in the U.S. where we are on 110 a.c. I'm probably the type of person some of your answers are aimed at but I do enjoy reading and eventually hope to see the solution. I have just enough knowledge to get myself into trouble so I will just read along and hope that if this ever happens to my saw, I will be able to find some nearby to get me back up and running again. I feel that Hegner stuff is vastly overpriced so if there is a way to fix anything without paying them their "ransom" I'd prefer to do so.

My thoughts entirely

 

[raythompson102]

I've found out a bit more. An integrated circuit U211B datasheet is used with a triac and the speed sensor to control the motor.
Quite a sophisticated approach. If the triac has failed that should be easy enough to change.

It is indeed the ic you mention, the U211B and looking at the data sheet I think diagrammed no.10 is probably the circuit diagrammed of my controller. I’ve asked Hegner for a price for a new PCB so I’ll wait and see what they come up with. If I can get a new one, you are welcome to have the old one to play with.