Stupid! Stupid!

Daniel Macina

Daniel Macina

Well-Known Member
I just did one of the stupidest things I've done in my life. A few weeks ago I was changing out the motor on my grinder and it slipped and dropped off the little 1/2" base just enough to pull the VFD wires out of the motor. Didn't hurt anything. So tonight I was getting it wired up again powered it on and POP! Lots of smoke. I thought what in the world! I knew I had wired it up just like the first time. I get to looking in the motor pot and I had missed the first time that there was a little exposed wire and these where the results. Bottom line 5 extra minutes of checking could save you $400! I just about puked when I saw it. That VFD was my pride and joy. IMG_1587.JPG
 
Check with KB (phone #s and address are on the manual bottom of back page). They may help you with this. Probably cost you something but not the price of a new VFD.

Let me know if I can help you.
 
That's a single layer board. Which means you should be able to just order the part that blew up and solder it in place of the old one. It looks like a capacitor of some kind. I'd contact the company and give them the part number that's on the front of the part. I don't think you're out a complete unit.
 
Well hopefully that the case! Bottom line when working with expensive equipment double and triple check that everything's good no exposed wire before plugging it in.
 
Daniel Macina said:
Well hopefully that the case! Bottom line when working with expensive equipment double and triple check that everything's good no exposed wire before plugging it in.
Click to expand...

I've done the same, or worse. I've caused many computer deaths in my career. Fortunately for me I had the tools and knowledge to fix most of my self-inflicted problems.

On a side note I haven't seen a single layer board in a piece of equipment in some time. I'm hoping there isn't something I'm not seeing that might make it otherwise. I'm sure the company will be able to tell you for certain better than me.

Good luck.
 
Can't read the numbers on the part next to the burnt part, but could well be a Triac, SCR, or some similar part. If you got really lucky, it only blew that one part. Could well have got something upstream of it also. Hard to tell from that photo.

Call K&B repair service, bet they can repair MUCH less than buying new.

Ken >
 
Looks like you burned out Q4 AND C74. "Q" on a PCB typically denotes a transistor, and "C" would be a capacitor, which in your photo appears to be missing completely. It may be bouncing around in the bottom of your chassis, or it could have exploded. If I had to guess, it may be the same value as the ceramic disc cap paird with the transistor just below the one that blew.

There's a chance that soldering in a new transistor and cap will get everything running again, but there's no way of knowing for sure that something else didn't get fried elsewhere on the board.

I'd give KB a call and see what your warranty looks like. If they don't want to repair it, or they quote you an outlandish repair price, you might think about just googling the numbers off of the burned parts and replacing them yourself. The two parts (if that's all that burned up) shouldn't cost more than $5 or $10 shipped, if I had to guess.
 
I did something similar with my very first VFD...... I contacted KBAC, and at the time, a new board was gona be just about $50 shy of a whole new VFD..... so I ponied up, purchased a new one, with a big note to self...... Don't do that again! :) That's been over a decade ago, so I have no idea how prices might have changed.
 
Well at least I'm not the only one! I called and left a message. I'm not expecting that it will be much cheaper then just buying new but we'll see.
 
That's not the worst thing that could happen. I think that any accident in the shop that doesn't cost you an important part of your body are not so bad.
A full 5 % of the customers in my sharpening shop (carpenters) are missing some fingers. Mostly from table saws.
The best we can do is buy the new part and consider ourselves lucky.
 
When you talk to KB ask if they offer a Power Board as a replacement part. They may not share component-level drawings so that you can get the individual solid state parts. Plus, my suspicions are that several of the traces probably burned up when the components popped. Unless you are experienced with circuit board troubleshooting and repair I’d get a new board and be done with it.

A power board is probably 1/3 the cost of a new drive, but that’s just a guess.
 
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