troubleshooting this board

[MarkM]

Hello everyone,
First off, sorry if this is the wrong section to post this.

I'm trying to troubleshoot these boards that control blower motors.
Two of them power the motor fine, but doesn't kick it into high speed; the other one I found a thermistor (SCK 203) blown and arc against a relay and a fuse blown. Replaced all three components with used ones and the fuse blown again. Looking for help trying to figure out what's wrong. Images attached of the board with bad fuse.

Thanks,
Mark

[budm]

Re: troubleshooting this board

What kind of motor is it? Voltage rating for the motor? AC/DC? etc. The more details we have the more we can figure how it works.

[MarkM]

Re: troubleshooting this board

Hi budm,
I can't find much info on these motors, they're 120vac. I attached images of what they look like, the motors are for boilers.

In hindsight what I thought was a relay appears to be a capacitor (image attached).

[budm]

Re: troubleshooting this board

That Grey cap is the safety cap used across the Hot and Neutral to filter out the noise from going into (or out of the unit) into the power line, it will not affect the function of the unit. I can see the tag on the motor, what does it show on the tag?

[MarkM]

Re: troubleshooting this board

HI budm,
Just took pictures of the tags on the motor.

[budm]

Re: troubleshooting this board

OK, I found the company website, I will need to look deeper to get more info.
http://www.ebmpapst.com/en/products/....php?pID=53652
This is going to be real hard to figure out the circuits on the board, you can do basic checking for shorts or open circuit of the components. You can start by checking those 4 TO-220 (it has metal tab with a hole on it), you will need to get the numbers as printed on the body and find out what they are, more likely to have some shorted out one.
There is also a bridge rectifier (a black flat pack with a slant cut on the corner) that needs to be check, and since you do have semi working board, you can do some resistance comparison reading between the boards.