Hampden engineering H-IEC-B4 PLC trainer.

[electronics-whiz]

A friend that teaches the electrical apprentice program at the local community college gave me a bunch of these old trainers from like the 80's. They used at one time, then I guess sat in storage for years and they cleaned up during a relocation they decided didn't need them.

This unit was made for 208, I removed the old banana input jacks he said it should run fine on 120V. I just put a 3C 120 cord on it and connected it up worked fine. I connected a fairly small blower motor it tripped the breaker/switch on the unit, (motor worked fine) I reset plugged in got small pop from the unit and breaker tripped again. The unit will power up fine, but soon as you turn the speed knob (PWM type drive) it will just trip the built-in breaker.

I looked things over I don't see any fuses, obvious blown caps, bad connections, or any holes/burn marks on anything. I see some resistors that when tested are like 1/2 the value it says they should be, but seems could be just because they are connected. I would think if a resistor failed if old carbon comp value would marginally change, or would just go open. Also noticed similar issue in a couple of potentiometers, seems is more issue of being connected though.

I noticed the transistors have a bit of a bulge in the top, but I think that is just package design. I see one cap with no vent on top that has a very small raise (hardly detectable) in the top as well as a ring in the center. They are mallory brand which I don't think is one of those junk cap brands.

I'll attach pictures I don't know you will spot anything I missed, but possible. If it means removing all the parts with odd values, etc I may just junk it as I have a small Allen Bradley PLC that if I can figure out how to program would do same thing and more in smaller package.