Just got a call from "Cuz." He's bringing all four PCBs in the morning. Wish me luck.

 

Apparently he is going to have to order a new control board. He brought three to me: one was incompatible and the other two had burned resistors. He wanted me to just replace the resistors, which I did. He has installed both boards and the motors don't run.

A new control board is about $400, and before he buys a new one and maybe fries it, we need to test the motors. They are marked 90VDC, .63A, 1/15 HP. Where would I come up with a power source to confirm that the motors will run?

Thanks.

 

Do you have a Variac? If so you can put a bridge on the output and bring it up slowly.
The other alternative is an automotive battery, fault should show up even at 12v test in both directions.
There are these SCR types of controllers on ebay for $15.00.
Those are quite small motors, Is the RPM set to a fixed speed?
Check the brushes for wear/length.
Max.

 

Apparently he is going to have to order a new control board. He brought three to me: one was incompatible and the other two had burned resistors. He wanted me to just replace the resistors, which I did. He has installed both boards and the motors don't run.

A new control board is about $400, and before he buys a new one and maybe fries it, we need to test the motors. They are marked 90VDC, .63A, 1/15 HP. Where would I come up with a power source to confirm that the motors will run?
...

A bench power supply 30v etc should get some movement out of those motors.

Re the control boards, you might be able to test by hooking up a mains rated light bulb, ie 60W 110v as a dummy load to pretend to be the motor.

That will work as a test in a lot of cases, normally they regulate motor speed by using some simple current feedback so the light bulb is not a perfect simulation of a motor, but you should still be able to turn the speed knob up and down and see if the light bulb gets brighter and dimmer.

I realize how an SCR bridge works, it is just very unusual to see such a large cap on SCR drive, these are more common on the PWM versions. ...

Sorry if that came out wrong Max! I know this is your area of expertise and was just commenting on the appearance of the circuit based on that one photo. A check of the part numbers on the two power devices will show if they are SCR (phase angle control) or IGBT (PWM).

Yeah I admit it's rare to see a big electro cap after a controlled rectifier, but when the circuit includes peak current limiting it can be done just fine.

 

It does appear by the part number that they are sensitive gate SCR's made by Teccor which are no longer, as they were taken over by LittleFuse.
Max.

 

It does appear by the part number that they are sensitive gate SCR's made by Teccor which are no longer, as they were taken over by LittleFuse.
Max.

I was unable to find a datasheet for the A69104 SCRs, but recent production of the boards still shows them in use.

 

For handling 90V 0.63A motors it hopefully shouldn't be too difficult to find substitute SCRs if those particular types are unavailable.

 

The company may have some years of anticipated stock which were obtained before the takeover.
I don't see them being too fussy as regards specs, the application is a very common one so you should not be tied to that particular part No IMO.
Max.

 

Apparently he is going to have to order a new control board. He brought three to me: two had burned resistors. He wanted me to just replace the resistors, which I did.
They are marked 90VDC, .63A, 1/15 HP.
Thanks.

If there seems like a common source of failure, maybe there is a bit of a design flaw?
There are many drives of that nature running larger H.P. motors than those, with high reliability.
Is it the 5 or 10w W.W. resistors that are failing?
These are usually the motor current source detection.
Max.

 

I just found buried in my records that Teccor stated that the S6010L subs the A69104.
Digikey have.
Max.

 

It has been a few months but would you still like help on your relatives ovens? I have worked on lincoln impinger ovens for 6 years at least once a week. Stooooopid designs but I know most of them by heart and know your problem backwards and forwards.