Treadmill motor problem

I have the 115V version of this motor control board with a similar drive issue. All functions of the treadmill work except for a total lack of drive to the belt motor.

The circuit board is a MECFU Rev.2 made by Digital Concepts of Missouri Inc. It's out of a Star Trac Pro S.

Anyone find a schematic for this bad boy? Any luck getting yours going EdgeHawk?
Just checked my SCR (S4035K) in-circuit and it measures 47.8 Ohms G <-> K in both directions.

Welcome to the forums.

That thread you posted in was a bit old - http://forum.allaboutcircuits.com/showthread.php?t=52933&page=4 - so now you have your own.

Post picks so we can look at it.

I've verified that the motor is fine. Connected it to a 13.5VDC 800mA supply and the belt turned with ease. With the motor disconnected from the MCB, I'm seeing 16.5VDC, however when connected, the motor doesn't even budge. Also when trying to increase/decrease the belt speed, the voltage actually drops to 15.5VDC instead of increasing. The speed sensor has been verified as well. Had to test it since the main fault that I'm receiving is "No sensor". I have a hunch it might be the SCR, but came here to see what you all think.

At first, I thought there may be a short somewhere as the board was very dirty. I cleaned it up as best as I can and retested it, but it's a no go. There is a thick glue covering most components, now mostly removed on the right side using Isopropyl alcohol.

With the meter connected to the MCB, D10 is dim, but with the motor connected, D10 does not light at all. Manually turning the belt will cause it to light up as well.

Load detection works as I get the "No motor" error if I disconnect the motor from the MCB.

http://support.startrac.com/documents/docs/637-1061A.pdf

skyblaster said:

With the motor disconnected from the MCB, I'm seeing 16.5VDC, however when connected, the motor doesn't even budge.

Click to expand...

Found out this is not entirely true. If I disconnect the motor, LED D10 begins to slowly light up and at this point if I connect the motor it will attempt to move for a split second.

Well, I've found one bad part so far. One of the MOSFET's (IRFP264) is cooked so I've ordered up a few replacements.

Between the SCR, power diode, and MOSFET's, which require thermal paste? Conductive or non-conductive?
The board was so dirty when I started that I could barely tell which had thermal paste installed.

All of em will need heat sink compound

skyblaster said:

Well, I've found one bad part so far. One of the MOSFET's (IRFP264) is cooked so I've ordered up a few replacements.

Click to expand...

Finally received my replacement parts (IRFP264N instead of IRFP264) and the treadmill is back in operation.

Thanks R!f@@ for the following image! It was very helpful in the absence of a schematic.

I am having a similar problem with my True 450 treadmill on the SS90 card. Do you think that the mosfets and SCRs are the same between the two?

sparkywolfe,
You are "hijacking" someone elses' topic - please don't do that.
Instead, post a link to the thread in question in a thread that you own.

When a Moderator sees this hijack, they will most likely move it to the end of the thread that you started, here: http://forum.allaboutcircuits.com/showthread.php?t=61507

For reference, the thread you hijacked is here:
http://forum.allaboutcircuits.com/showthread.php?t=56264

As far as your question; the diodes and thyristors are in different packages than those on your board - so they are certainly not the same.

If you start by cleaning your board, we might be able to figure out what the part numbers are - even if only SOME of the numbers are still visible.