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What a disaster! KBIC DC Drive

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Hollowpoint10/02/2021 13:18:59
433 forum posts
53 photos

Over the past few evenings I've been working on a new drive and motor for my Cowells lathe, I chose to go with a KBIC controller and a DC motor since they are readily available in small sizes.

I was nearing completion and decided to check everything was wired up and running correctly before installation, which it was.

But then with just a small repositioning of the mains cable (which seemed to want throw itself of my bench) the whole lot went BANG! sad

Many many swear words later...

Inspection found I forgot to connect the earth wire to anything and the ringed connector at the end had touched one of the components on the circuit board shorting it. angry

So now I'm left with this:

So my question is, Do you think it is worth trying to fix? I imagine its doable but very tricky. The biggest problem I can fore see is that I don't know the value of the burnt resistor? Anyone have the same board? There is also the potential that other components are fried too.

Should I just cut my losses and buy a new board (£100+) crying

John Haine10/02/2021 13:24:08
4096 forum posts
241 photos

You probably know this but there should not be ANY earth connection to the KBIC board itself, as its "common" connection actually floats at half mains voltage since there isn't an isolating transformer. This can be an issue trying to control DC motor speed from a CNC controller, some form of isolation is needed. By all means earth the metalwork of the lathe and motor but keep the KBIC wiring well away.

Hollowpoint10/02/2021 13:27:56
433 forum posts
53 photos
Posted by John Haine on 10/02/2021 13:24:08:

You probably know this but there should not be ANY earth connection to the KBIC board itself, as its "common" connection actually floats at half mains voltage since there isn't an isolating transformer. This can be an issue trying to control DC motor speed from a CNC controller, some form of isolation is needed. By all means earth the metalwork of the lathe and motor but keep the KBIC wiring well away.

This was the mains input wire that wasn't wired up to anything on the board itself, I had just fitted a ring connector ready to earth the lathe/metalwork as you say.

Rockingdodge10/02/2021 13:29:46
avatar
284 forum posts
52 photos

What KBIC board is it? There does seem to be schematics available so should be possible to id the blown resistor and any others required.

Roger

Simon036210/02/2021 13:35:15
219 forum posts
77 photos

"Nothing ventured, nothing gained....."

I would personally:

  • replace the track with a piece of wirewrap wire - or something as fine as possible
  • replace the dead resistor with a 'full size' 1/8 or 1/4 W leaded version which should make access easier for test purposes

reconnect, avoiding all the previous errors. If it works, great, saved $100.....if not, I would assume that the damage has propagated through other components and its for the recycle bin.

My 2c.....good luck

Hollowpoint10/02/2021 13:36:29
433 forum posts
53 photos
Posted by Rockingdodge on 10/02/2021 13:29:46:

What KBIC board is it? There does seem to be schematics available so should be possible to id the blown resistor and any others required.

Roger

Not entirely sure but It's a slightly older one,

KBIC or KBMM 240-D

KB A57540

Rev - B01

230v or 115v input

90v or 180v output

Edited By Hollowpoint on 10/02/2021 13:38:02

noel shelley10/02/2021 13:39:56
711 forum posts
19 photos

Anything is worth a try. but don't expect miracles. If all that has gone is a blown track and a resistor your a lucky man ! Surface mount does not always make it easy to remove or replace components. Good luck Noel.

Rockingdodge10/02/2021 14:19:23
avatar
284 forum posts
52 photos

This link might or might not help KB Electronics - Manuals

Hollowpoint10/02/2021 15:55:12
433 forum posts
53 photos
Posted by Rockingdodge on 10/02/2021 14:19:23:

This link might or might not help KB Electronics - Manuals

Thanks for that, Lots of useful information there, Unfortunately I can't find any info about the resistor value.

I might have a go at fixing it in the manner suggested by Simon above. Though I suspect I will still end up having to buy a new board.

Howard Lewis10/02/2021 16:04:50
5228 forum posts
13 photos

Maybe the manual will show what value the resistor should be.

Presumably yours is fried so that the colour code is no longer visible?

Howard

John Haine10/02/2021 16:11:23
4096 forum posts
241 photos

SMD - no colour code...

Hollowpoint10/02/2021 16:29:59
433 forum posts
53 photos

Yes no colour code, just a number printed on the top, I cant make out the number because its burnt.

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