View Full Version : Bridgeport interact 4 help / advice needed.

18-08-2020, 07:51 PM
Hi all,

I have to preface this post by saying that I'm not a CNC person and I barely understand what I'm on about.

A friend of mine has Bridgeport interact 4 with Heidenhain TNC 2500 controller.
Machine is, aside from non working spindle, in fantastic condition. All surfaces are still completely covered with scraping marks. Spindle is controlled by Mentor II drive and some of the smd / resistor caps at the bottom of the MDA75R board are burned as per picture. The motor itself is some Italian DC motor (tag from the motor included too). Please advise on the best way to get this machine working bearing in mind that he doesn't have too much money.


If someone has a similar board and can take hires pic of the part that's burned so I can just replace smd components, that would be absolutely AWESOME.

Regards JJL.

18-08-2020, 08:35 PM
You really need the schematic diagram. The SMD caps don't generally have markings and you may also struggle to identify the smaller semiconductors. Looks to me as if the board is severely roasted, so a lot of the tracks may be geography now. Speaking as a power electronics engineer, I'd say your chances of success are limited.

But the cause of the blowup may be the big switching devices rather than the drive circuit on the board. To the left of the photo you can see a glimpse of one of these - have you tested them to see if they are OK?

It seems these drives are rather prone to popping. There was a guy over on another forum very recently (not sure now which one) with a similar issue although I don't know how he got on trying to replace the controller. The motor has both a stator (stationary) winding and a rotor winding, requiring a control circuit for each. It may be simpler to swap for something more conventional like an induction motor and a VFD although this sounds mechanically painful.

18-08-2020, 10:40 PM
The thread was on here.- http://www.mycncuk.com/threads/13876-Can-anyone-help-me-with-ideas-for-driving-a-med-large-dc-spindle-drive-motor-please

18-08-2020, 11:57 PM
Hi Muzzer,

Thanks very much for taking the time. Appreciated. The picture, to me, looks worse in the picture than in real life. None of the copper traces on the pcb look blown, but I could be wrong. I was thinking about cleaning the burnt area with 99% alch and see how it looks then. I do understand your point on caps. I would imagine that schematic diagram for MENTOR II DC drive is going to be impossible to find. I found a place that can repair / replace those boards at 700+VAT but my worry is what caused the problem in the first place. The last thing that I want to do is to advise someone to send that DC drive for repair and than it turns out that something else is causing the problem.

The idea of replacing the motor with something current is very appealing given that mechanically machine looks brand new when you look at the surfaces.

Once again, your help is very much appreciated.

Regards, JJL

18-08-2020, 11:57 PM
Hi, M_C.
Thanks for that, I'm going to read that thread now and try to make some sense out of it.

Regards, JJL

19-08-2020, 09:27 AM
I suspect what you are referring to as surface scraping is actually the pattern used to retain oil on one of the mating surfaces of the slide ways. By the time that had worn way you'd be looking at a very badly worn machine. The pattern is added after the slideways have been trued up. Creating them makes no difference to the accuracy of the machine. You will most likely find that the mating surface is unscraped and may also be chromed for wear resistance.

However, it does sound as if it's a good example and despite the damage to the board, everything else looks very clean and tidy.

19-08-2020, 11:15 AM
Thanks Muzzer,

I see. I've tried to be clever and used the logic of what I've read about lathe slideways. It's obviously different on milling machines. Quotes for repairing the board are about 6-700 My worry is that once repaired/replaced, whatever caused burnout in the first place will damage the board again. Could you be so kind to give me an idea, or even better a link to the new motor drive combo that you'd install in a Bridgeport interact with tnc2500. Also, how easy/difficult would be to replace tnc2500 with something like linuxcnc or equivalent modern cnc setup.

Your help is very much appreciated.

Regards JJL.