A friend bought a KBIC-120 controller to use with a treadmill motor on his lathe. He hooked it up per the manual, but it blows the AC fuse immediatly at turn on. Loud pop. I have the controller on my bench. I have checked his hook up and it was correct. He has the correct fuse, and correct power resistor for 1 hp motor. motor is a PM type.
Anyone have experience troubleshooting KBIC SCR controllers? Help! at this point, with all connections removed except the ac in and the fuse, it still blows fuses. Help please!

Chuck in E. TN

Is the type of fuse as well as its rating correct? You may need a slow blow rather than a quick blow fuse.

The fuse in the AC line is as recommended by KB. The fuse blows with a loud pop indicating to me that a dead short exists, w/o the motor even hooked up.
I downloaded KB's checklist for troublshooting and all resistance checks fail. I emailed KB asking for a parts diagram so I could try replacing the diodes called out by the Troubleshooting guide, and they don't supply one. They also said by my description the controller was hosed.

Chuck in E. TN

You could try removing MOV1 and C23 temporarily and then reconnecting the KBIC to 110Vac. If it doesn't blow the fuse when you do this then replace MOV1 ( V275LA20A ) and C23 ( 0.047uF 250Vac ) with new parts. You could also try replacing D13 and D14 with new parts ( sorry don't have type numbers for these ). Capacitors and MOVs across the ac mains live and neutral are more likely to fail in the US than in Europe because you have more thunderstorm induced surges. If your KBIC is a different revision to mine the parts numbers may be different but you should be able to locate the corresponding devices fairly easily. If you aren't confident about messing with the KBIC then junk it and buy a new one - they aren't very expensive.

Hi There,

I just fixed two KBIC-120s. One had been overvoltaged to the point some traces on the back were "opened" by melting. The other one looked to me like it had been hit by lightning or a very high voltage spike.

In the later KBIC's case I found that at least one of the SCR's was blown. The MOV mentioned above was also damaged. I had to remove the MOV and both SCRs to find the one blown.

A simple check you could make is to OHM out the two AC inputs L1 and L2 -- they should not have continuity. If there is continuity the board has been damaged. In the blown board above I could use my OHM meter's continuity check (beeps) to check this.

From the symptom you described, I would guess some of the components are blown.

I haven't found a replacement SCR part number for the A69154 (Teccor) SCR on the KBIC. I believe Little-Fuse bought out Teccor. Digikey has a "case isolated" SCR that looks like a fit but I'm still trying to find an old datasheet so I can confirm the power rating needed. Don't want to put one in that has too small or too large a power rating as either can be a problem.

I'm not sure what function the MOV has in KB's circuit (over voltage?/Lightning suppression/Noise Suppresion -- I'm not positive) I haven't personnally looked up the MOV's replacement -- I trust the value above is correct. I was able to use a MOV off of another KBIC I am troubleshooting for the time being.

If I find the right datasheet I'll post an equivilent current SCR. The Diodes are also candidates for trouble (The SCRs and Diodes i'm referring to are mounted in the vertical against the metal backplate). You could use a multimeter with diode check to see if any of the were blown.

As another option, you can find them on Ebay for $20-$40 pretty regularly. So if you aren't an electronics type it might be less frustating to just try a different KBIC as your friends sounds damaged.

The MOVs are there to prevent spikes on the ac mains from damaging the KBIC drive circuitry and also to keep spikes generated by the KBIC from feeding back into the ac mains. The part number I gave for the MOV was for the 240Vac version of the KBIC. The 275 in the part number stands for the voltage and the 20A is related to the current rating. In the US you could use a V130LA20A. The V275LA20A wouldn't cause any problems but would let through spikes between 130 and 275V which the V130LA20A would catch. Having said all that I doubt if it matters which MOV you fit. MOVs don't last for ever and they fail short circuit.

Just let me clarify the statement I made in my previous post. You can use MOVs with either of the part numbers I mentioned, NOT just any old MOV .