View Full Version : I just blew my 7x lathe controller board

05-27-2010, 04:14 PM
It blew the fuse with thunder and lightning. When I replace the fuse it keeps blowing it immediately.

I have visually checked the controller board and there seems to be some evidence that one or maybe two components have released their magic smoke.

They are marked D13 and D14 so I guess they are diodes although they have three legs and TO220 capsules. But I can't find neither the diodes nor their datasheets anywhere so I'm kind of stuck. Does anyone know anythin about them?

One is marked with "D8010L" and "A6" on separate rows and the other "D8010L" and "E6".


05-27-2010, 04:58 PM
D8010 is a 10A rectifier diode. A69108 is an SCR.

05-27-2010, 05:18 PM
Thanks. What do you think of this as a replacement?

05-28-2010, 03:35 AM
I still haven't found a datasheet for the D8010L, but I have found one for D8015L here:

If I check the data against the 8015 I guess I'm on the safe side. I think I'm going to try these, since they are in stock:

1200 V/20 A should give me some margin over the original 800 V/10 A. What the datasheet does not tell me though is if the capsule is isolated. I will have to find that out and mount them isolated if not.

05-28-2010, 04:07 AM
A couple things to consider. (Yes I realize you are not in the USA)

There is a firm that repairs those controllers:


Trouble shooting info here:


Choose the 'troubleshooting variable speed drive' That will download a PDF.

LMS also stocks some of the FETs and such for those machines.

Lastly, you can replace the controller with an MC-60 DC controller from a treadmill. They run about $40 on FeeBay.

Good luck.

05-28-2010, 04:34 AM
My controller is not of the same type as thse pictured in the LMS guide, or those sold by LMS or Arc Euro Trade as spares. The large semiconductors on my controller are two SCRs and three diodes, while the more common controllers feature two mosfet transistors. But yes, I guess plan B if my repair fails is to replace the entire controller board with something more common.

I ordered three diodes now and will pick them up after work. I hope exchanging them will fix it. I desperately need my lathe - to finish the CNCing of my lathe :o

05-28-2010, 11:27 AM
pretty much any electroncis repair sop shoulbe able to fix it, that or goto and place that sell parts and pick up what you need and replace them your self its really very easy to do if you know which parts are broken take them out and get new ones and solder them in..

05-28-2010, 11:52 AM
If it's not the diodes or the SCRs I'll probably give up and get a generic replacement. My knowledge in electronics is pretty dated by now, having never worked with it after school, and I just want to get it running quick so I can get on with the more creative things. If I could find a repair shop here that wanted to touch it, they would probably charge more just to give an estimate than the board is worth.

But I have the replacement diodes now and will report back when I have failed.

05-28-2010, 12:39 PM
I'll be damned. I thought I had bought a genuine chinese product, but look at this. It seems to be very true that you can never trust the manufacturers promises of country of origin! ;-)


I wonder if this is broken? :p


Judging by the appearence of the legs I'd guess the cause of death must have been swarf getting in the box and creating a short circuit between them. But that wouldn't kill a diode, or would it? Maybe the heat?

05-28-2010, 02:03 PM
If you want to get a new controller, check out LittleMachineshop...

it may be this one...


05-28-2010, 04:19 PM
I desoldered the diode with visible damage, and out of the board it was easy to confirm that it conducted both ways. So i swapped it for a new one - and the lathe is running again! :) :)

Now on to using the lathe to cnc itself.

05-28-2010, 05:34 PM
That's really great news! Glad you sorted it out with minumal fuss.

That KB controller is better than the stock unit supplied on the 7x lathes. I had a 7x10 and the controller died just out of warranty.... H-F would not do anything for me.

I put an MC-60 treadmill controller on the thing and it worked great!

05-28-2010, 08:14 PM
So it appears that the diode shorted for some reason. Could be that it wasn't properly coupled to the heatsink, or maybe a voltage surge occurred on the input. If a voltage surge caused it, that raises the question of using a surge protector in line before the VFD. I'm bringing this up because some companies that make surge protectors extend some kind of guarantee towards damaged equipment. I'm not sure how far you could go with that if you made a claim, but the very idea of using a surge protector before any of this electronic machine power supply gear is worth considering.

Back to the failed diode- I have seen many instances where the power device (the diode in this case) is not held in contact with the heatsink properly. This could be because the heatsink material gets raised up when the screw is put in, and thus the device can't be made to sit flush on the surface, or the area of the device where the active silicon material is doesn't sit in contact even though the area where the screw goes through does. I've seen it time and again, and what appears to work best is when the body of the device is pinched towards the heatsink by a flat spring type of thing. Usually, a bar of sorts spans two devices, and a single screw between them applies the pressure. A small pad of rubber over each device keeps the pressure applied more or less centered on the device so it gets held down evenly. This pressure is directly above the active area and is where the heat is generated, so that is where the intimate contact between the device and the heatsink should be.

05-29-2010, 11:16 AM
I'm pretty sure it died because of arcs and heat created when the legs were shorted by swarf. The photo is pretty bad, but if you look carefully you can see that the legs are almost burnt off, with small pearls of metal in the burn. If it had failed due to internal heat I would think that the damage would by mostly internal as well since the conductors are thinner there.

05-29-2010, 11:30 AM

This just confirm the fact, that what makes electronic works is the smoke inside, as soon as this smoke gets out, the apparatus does'nt work anymore :p

05-29-2010, 01:57 PM
Well, two good things- one is that you pretty much know what the cause was. At least then you know what can be done to prevent it from happening again. The other good thing is that the damage occurred early in the circuitry. If a chip had gotten into the later stages you could have fried a lot more parts, and that probably would have made the controller a write-off.

Ironic- many of us talk about the magic smoke- well, in the fabrication of a lot of those parts, it is in actual fact a deposition of 'smoke' that makes the part what it is. Vapor deposition. And the magic? All it takes for me is to see these latest gadgets that people are carrying around these days. We thought that the Dick Tracy wristwatch tv was a futuristic fantasy. It just blows me away what capabilities come in small packages now. Just last night I was in a pub, and two women were sitting there, at the same table, typing away at each other, laughing their faces off. Heh, I guess in an environment where you can't even hear yourself yell, that's one way to communicate.

Nest thing you know, it'll be implants. You look at people and it'll look like their talking to themselves and joking to themselves. You won't even see the electronic devices. In my day they'd put you away for such behavior :)

05-12-2012, 12:44 AM
I disagree. I think the stock chinese one is better for the lathe. They are a PWM drive which has better low end torque. SCR drives trigger at 120Hz and make more noise with lower and not as smooth power.

My original drive went bad and Grizzly sent me one out of a mini mill. Real nice drive. A lot of power for the size.