FMC Wheel Balancer Repair:

Click on the pictures to zoom in.

I'm documenting the repairs we made to it. If you find this page useful, drop me an email.

This picture shows the machine after we completed the repairs.

1. The Brake was always stuck on. A soft hum came from the machine when the power was turned on.

(This picture shows the machine after we completed the repairs.)

We found the MOSFET that controls the brake relay was shorted and kept the relay closed all the time. Replacing the MOSFET did not solve the problem right away so we dug further.

Turns out the 7406 that controls the MOSFET was blown too.  A quick trip to the junk board pile produced a 7406. We replaced that and then the brake system started working.

I substituted in a MOSFET I had on hand. two of the pins needed to be swapped but the part worked good.

After hours of study, I realized that the connectors on the main PCB are labeled (right to left) P2, P1, P3, P4, P5.

We had swapped P1 and P2 by accident.

Once we had all the connectors in properly, the machine worked great!

This is a picture of my friend reassembling the machine.

Here is a link to Steve Roger's web.  Steve is a Sr. Project Engineer at Snap-On.

http://www.stevewrogers.com

I followed the links on his Resume page and got all sorts of good information about how the machine works from the patent office. (Very helpful!)

Thanks Steve.

Here are the links:

Calibration procedures:

I got this of the web! It may be similar to your machine.

 FMC 5800 calibration procedure

real easy'
1. turn balancer off then on again
2. push F then 1 then spin, display will read "cal slg"
3. take calibration slug off back of unit and screw into hole in backing plate
4. lower guard and spin wheel display will read cal 0
5. remove cal slug and respin display will read cal 600 d
 

I found this out on the web too!

http://www.agequipment.co.uk/
http://www.agequipment.co.uk/fmccal.html

FMC2500 cal procedure