That version appears identical to the one I have, MC2100LS-30
Did you see the reverse engineered schematic posted previously?
R17 & D9 is R21 & D10 on this board.
Max.

 

this one:
https://forum.allaboutcircuits.com/attachments/mc2100_rev_engrd-pdf.152059/
My C13 would be C12 on the schematic.
Where is R22?

 

R22 does not show up on that version, I will have to remove the board from the chassis to find out its purpose (R22).
Max.

 

On my board one side goes from one pin from C13 (link between C13 and the big C7) the other goes to the array of resistors near Q1 and it also connect to U4

 

I replaced the the R21 and R22 resistors with 470 and 140 Ohms. I also replaced the IRFP250M.
Flip the switch... It ran for about 5 min. I could control the speed of the belt. Then it stopped (light flashing) . I think the IRFP250M is short again. It is not totally conducting between Source and drain but I have a very low resistance both direction.
So I am back to square one, as soon as a speed is asked at the console, the DC to the motor goes to 150V.
I can test this with the motor disconnected or with a lamp connected .
The voltage at the rectifier(DB1) is only 103 VDC. How can that jump to 150V?
I suspect the motor is drawing more than 30 A as the MOSFET IRFP250M is damaged. What do you think is causing that?

 

When the micro sends a command to the mosfet, it also ramps up the voltage to the motor through the SCR, is the voltage off until then? It should ramp down again when the command switches off.
Max.

 

Yes, voltage off, when I select start, it ramps and when I select off it decreases. All that without the motor.
When I tried it with the motor connected, it ramps up then the MosFet burnt and it was stopped by the board (flashing light) .

 

Newbie here. I have the same board with apparently the same symptoms. The usual suspect components mentioned above check out. There is power all the way to the console (I replaced with PWM signal generator; see photo), but no power to motor leads. The curious thing with this one is that the LED is very very dim, and with a faint inconsistent flicker (like poor connection) even when PWM is off. Does the faint LED suggest a culprit to anyone? Thanks.

 

Check voltage at DB1 external pins. Should read over 100 VDC

 

Check the 5v at the micro power pins, this version uses a different method of 5v power for this purpose, I intend to reverse engineer how it is done, as it is different to the more common MC2100 versions.
Max.

 

Forgive me, which are the "micro power pins"? The 5 pins next to the LED? And how to test the voltage there? Thanks.

 

The power on the micro is 5vdc on pins 10 & 20.
The 5v supply is RG3 fed from the 15vdc RG5, see if you have the 15vdc OK also.
Max.

 

@lambalain The DB1 external pins show ~106Vdc.

@MaxHeadRoom By "micro pins" do you mean the 20 pin micro-controller at upper left of board? If pins 10 & 20 are the 2 "bottom" pins (furthest from the heat sink), I can report ~2.9V between them. I'll guess that's low. I do not see an RG5; but RG2 goes from 12.5V in to 5V out, and RG3 (could be 4) goes from ~5.5V in to ~3.8V out. I'll guess that's low, too. On my other board (MC-2100LS-30) RG3 goes from ~14.5V->5V. So, perhaps RG3 is bad? Or is something before it is bad? Thanks.

 

On the board I have which is very close to the one you show, the micro has 20pins here is the sheet on it.
RG3 looks like it is supplying the correct voltage to the micro. Many of these boards differ slightly in the other supply LV which can be anywhere from 12v to 16vdc.
When the micro sends a command to the Mosfet, the SCR turns on the HV to it.
The two outer pins of the bridge rectifier should be ~105vdc.
Max.
.

 

"RG3 looks like it is supplying the correct voltage to the micro."

Which RG3 value are you referring to as correct? The one from the faulty board is 5.5V -> 3.8V? Or the one from my good board 14.5V -> 5V? By the way I don't see a "sheet" attached to the post. Thanks.

 

Giomonte: can you give me the color code or value for the 2 resistors R21 and R22.
Since you have an identical board to mine, I would like to confirm I have the right values.
Thanks.

 

Forgot to post it.
RG3 should be 15vdc in and 5vdc out.

 

Giomonte: can you give me the color code or value for the 2 resistors R21 and R22.

--------- LT ------ (LS-30)---- color code (best I can tell)
-------------------------------------------------------------
R21: . 506ohm .. (508ohm) ... green, red, red, black, red
R22: . 131ohm .. (136ohm) ... red, black, black, red, red

 

Forgot to post it.
RG3 should be 15vdc in and 5vdc out.

Thanks! So, does this mean RG3 is bad, or is something before it bad?

I also just verified that the micro is getting 3.8V at pins 10 & 20, same as output from RG3.

 

Something appears to be loading it, hence the LED flicker?
Is the micro getting warm to the touch?
Max.