Help to repair my Variable Speed DC Controller

[ngr1]

Hello, in playing around with my DC speed controller I managed to break it by touching the ground wire to the heat sink which in turn caused a large spark and blew the fuse. I have replaced the fuse 3 times and each case it was blown again as soon as I turned the unit on.

I removed the board from the case looking for blown line in the circuit board but I could not find one so I am assuming one or more components on the board has been fried. I looked for any obvious burn marks on the individual components but found none.

By reading this you have already surmised my electronics skills are very low, which is true. Any electronic gurus who are willing to guide me as to how troubleshoot this problem without killing myself? I am hoping the solution is a replacement of one or more components that I can do myself.

BTW, this controller was to be used to upgrade my TAIG CNC mill and the output when working was a constant 170 Volts at high and low speed settings.

Any help would be appreciated.

Thanks!

[Al_The_Man]

I see your flash mark on the HS.
The fact that you had a constant 170v and the large Cap, would indicate is most likely a PWM drive.
You may have to do a bit of reverse-engineering.
It obviously points to one of the solid state components on the heatsink, I would unscrew the fastening screws and remove the HS components one at a time and identify by part number, download the spec sheet, and test them for shorts between pins.
Al.

[ngr1]

Thanks for the feedback Al.

What exactly are those solid state components on the heatsink called?

I have googled the info (part #s) on them but have not come up with anything meaningful, can someone recommend a site to find info on these components?

Thanks!

[Al_The_Man]

If they are In-House numbers, then you may be out of luck, what are the numbers? Maybe someone will recognize them.
Al.

[ngr1]

The large solid state component connected directly to the power terminal is SKBJ10J (or maybe SKBJIOJ) and M524 SMSC.

The other two i will need to magnify.

What are these components called? Solid State Relay?

Thanks.

[ngr1]

OK, I found the component. The part # is SKBJ10J and it can be found in China so i need to see if i can order it online.

Thanks Al.

[ngr1]

I forgot to ask, can i test a single phase bridge rectifier with a simple digital meter so i know which one to replace?

Thanks!

[Al_The_Man]

You can if it has a short on it, which if this is what is blowing the fuses, would be the cause.
With a normal ohms range, it should show pretty much open between any two leads.
For normal rectifier checking you need a meter with a diode test position, as the normal resistance range will not forward conduct the rectifier sufficiently to test.
If it is the bridge, you should be able to find something here that will suit, even if it is a different case style and just hard wire it in.
Al.

[ViperTX]

Do you see that large circular component looks like it is inline with the fuse...looks like a large black ceramic capacitor....I bet it is a varistor and is most likely the problem.

Paul

[ngr1]

Gentlemen thanks for your help thus far. I have an update.

I changed the bridge rectifier the variable control now works but only at full speed. The potentiometer was successfully tested using a meter so that can be ruled out.

Any ideas what else could have been blown?

Could the other bridge rectifiers be blown also?

Thx!

[Al_The_Man]

If it is a 2 quadrant SCR drive the SCR's could be blown, if a PWM drive the Power FET's or IGBT's could likewise be blown.
Al.