Problem with Hegner HDB200XL Speed Control

[howlingbaboon]

Hi All,
We've got a problem with our Hegner HDB200XL lathe in the workshop. Somewhere around speed 3 (if not slightly under) it just randomly fires up to full speed without warning. This can be somewhat frightening, especially if you have a large piece mounted. It's fine with the speeds above and below that so you can work around it but it's hardly ideal. I can't remember which if the 3 speed sets it's on as I haven't been able to get in for a while. When I do I'll check and see if it also does it on the other 2.

I've contacted Hegner to no avail as they no longer support or manufacture these machines. They only said that this means that there is a problem with the inverter.

Anyone know if this is fixable or, failing that, replaceable?
Cheers
Dave

[APH]

I assume this is in the community workshop you've mentioned ? If so, they ought to get a qualified electrician to look at it.
It could be something as simple as a new potentiometer needed (that's the component the speed knob's mounted on) or something more serious.

One quick and easy thing to try is firstly give the control box a good  vacuum clean, then when the power is totally off, vigorously rotate the speed control knob back and forth a lot. If it is a dodgy potentiometer it may help clean it up a bit, but be warned it could also move any debris around inside the component and you might find a similar issue at a different point in it's range.

I occasionally have a similar issue with VS controller on my lathe and the spin it about trick usually works. I just haven't bothered to put in a new potentiometer yet. A simple job IF you know what you're doing, if even slightly unsure get in an electrician.

[Doofusme]

Get your self some of this https://www.amazon.co.uk/gp/search/ref=a9_sc_1?rh=i%3Aaps%2Ck%3Apotentiometer+cleaner&keywords=potentiometer+cleaner&ie=UTF8&qid=1505820244

and give it a good squirt in the pot, should clear the problem if not a replacement pot is needed.

Cheers
Phil

[APH]

Get your self some of this.....

Again great care is needed using products like this, certainly isolate from the mains supply as a first step.

Actually getting sprays into the working parts of of a potentiometer isn't easy and, if you're unlucky, may even force more debris into the working parts and make the matter even worse.

[Derwent Woodturning club]

I've contacted Hegner to no avail as they no longer support or manufacture these machines. They only said that this means that there is a problem with the inverter.

Hi Dave,
Sorry to hear you've got problems with the lathe, but I very much doubt it is a problem with the actual inverter, more likely to be the control potentiometer behind the speed control knob.
I notice Phil has suggested using some switch cleaner but before spending any money, may I suggest giving it a good clean with compressed air, as the usual culprit in our environments is dust rather than corrosion. Some of those cleaners cause the dust to 'clump' and remain in place.
After that there are various things to try with a meter, but not knowing your background, I am a bit reluctant to go any further on here. Please don't take that as an insult, it's for your own safety as there will be a mix of 12V and 415V inside your control box, and I would not want to be responsible for a serious accident.
I would be happy to come and take a look but that does depend on your location.

[howlingbaboon]

Thanks for the advice guys! Yes it's the lathe in the community makerspace. I'll attempt the dry solutions first then and failing that I'll try and get a pro to have a look as I am no expert in electricals or mechanics. I'll be thrilled if that solves the problem as I feared that the problem might be harder to fix.

The other task is to replace the drive belt as it keep slipping with even light cuts. One thing after another eh!