Trying to combine a scr voltage regulator with the remaining guts of a PC power supply

Thread Starter

serkel

Joined Sep 8, 2014
10
So, hello every one. First time posting and probably no the last. A couple of weeks as a retired person I decide to build a 2x72" belt sander. It requires a bit of steel and a motor. The minimum used should be 1.5hp. I only had 1/2 hp. (2 of them) , then I discovered that some people have built them using treadmill motor, perfect! I salvage two from the scrap heap, one was submerge in water and the other was fine. The one in water has the MC 60 control board with some damage( to be repaired later) and the second one has a MC2100, which I understand will need a PWM in order to work, I got the parts for the build but impatient.

I have a on PC power supply that I would to use the case, the fan, and add an led to put that I can put a AC 220V 10000W High Power SCR Motor Speed Controller Voltage Regulator (from Amazon) to operate the DC motor that came out of the treadmill.

What do I need to the do to make it work?. I could use the case, install the regulator with a bridge rectifier, leave the fan in but provide a 12vdc source (an old phone charger power supply ) and forget about the LED.

I did electronics in the 90's when I was apprenticing electrician, but dabble in it a few time since. I have a great Fluke multi-meter and a few resistors and have access to a local supply store.

I would really appreciate you help, if you can

Thanks
 

MaxHeadRoom

Joined Jul 18, 2013
23,908
Neither the MC60 (SCR bridge version) or the MC2100 (PWM Output), requires a power supply, all you need for the MC-60 is a 5k linear potentiometer.
If you use a Triac controller you will need a DC bridge rectifier.
So all you need the 12vdc is for the fan?
Why not get a small AC one, and don't bother with any 12v supply?.
Max.
 

Thread Starter

serkel

Joined Sep 8, 2014
10
Neither the MC60 (SCR bridge version) or the MC2100 (PWM Output), requires a power supply, all you need for the MC-60 is a 5k linear potentiometer.
If you use a Triac controller you will need a DC bridge rectifier.
So all you need the 12vdc is for the fan?
Why not get a small AC one, and don't bother with any 12v supply?.
Max.
So sorry for not responding sooner.
You're right I don't' need a power supply to use the MC-60. I did attach a 10k potentiometer and nothing happen the motor didn't even buzz, but all 3 out of four LED did light up. Turned everything off and looked closer to the board and noticed that one end of R38 was bent back towards the wall of the heat sink, then the 5watt 5.6 K Ω had a bunch of rust, at its base. I wiggle it and it came off the board. Another thing I noticed that was missing was RPS1 which I believe that would be R42. As for the fan I have two reason I was aiming for the 12vdc, 1- I'm cheap or thrifty, and 2- I have 3 different sizes. Hopefully we can salvage my MC-60. As you can see I'm exploring all my options.
 

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Thread Starter

serkel

Joined Sep 8, 2014
10
Ooops One thing I forgot to mention that the MC-60 was in a flooded basement. When it dried the motor for the inclined portion worked but the motor did not. I have examined the motor. It whines a little until I help turning the flywheel that is attached to the motor. I need to replace the bearings and probably polish some of the parts to remove the rust. I have no idea how long the board was underwater,.
 

MaxHeadRoom

Joined Jul 18, 2013
23,908
There is quite a bit of info here in previous post as a search should uncover.
The motor should be dried and blown out using an air line etc, test it on a 12v automotive battery, for most applications the flywheel can/should be removed.
Its original purpose is often no longer needed in most typical applications.
Max.
 

Thread Starter

serkel

Joined Sep 8, 2014
10
Update Max
I will get a 110 muffin fan. Found a better treadmill motor. After cleaning the board with some circuit board cleaner and some alcohol I replaced the 5 watt resistor that appeared to be damaged.
l wired the to the motor to the board, added a 5k pot, plug it in, nothing the motor did not come on., all the led's came on. For the life of me I did not pay attention to which was on or blinking. After reading some posts, I started checking components with my meter. I then discovered that two of the SCR were bad , based on checking them as diodes, then someone else mention it cannot be done with a meter. In any case three out 5 read between 510 and 515Ω . Replaced both. Fired the controller board with a 5 k pot, motor started at full speed. At first I thought I wired the pot wrong, nope! Switch the wire around, not the issue, what else must check and replace. I have a good meter but no scope! What else do I check/replace? I saw something about the possibility of the MOC3052 being bad, could that becomponent be the root cause for no speed control.
 

Thread Starter

serkel

Joined Sep 8, 2014
10
the motor was connected, and none of the LED were on. I have to find a better source that does not charge as much for shipping. Mouser charges a minimum of 7.99 for a $1.00 IC. There are numerous version ,which one to take?
 

MaxHeadRoom

Joined Jul 18, 2013
23,908
Probably any of the random phase version would work, but if having to order one, use the original part No.
D6 monitors the input to the MOC. Unless the diode has blown.
You could always remove the MOC and see if the motor turns off.
Max.
 
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Thread Starter

serkel

Joined Sep 8, 2014
10
Well after painstakingly removing the MOC, I reassembled everything back together to test, plug it in , motor went full blast, no control of the motor. I did no check the D6 if its blown, that will the next thing I do. When I say painstakingly, I really mean it. Two weeks ago Friday I had my 6th surgery on my hand due to table saw accident, almost two years ago. The hand is still in a splint, I use my thumb and the side of the hand (where chop sticks would sit) to hold the soldering iron. What else ? I don't want to give up yet and get one that already works.
 

Thread Starter

serkel

Joined Sep 8, 2014
10
You will have to forgive my limited experience of electronics, but which part is the SCR bridge? Are we talking of one particular component, or a combination of a few to make a bridge? Remember I did change 2 of the 3 components attached to the heat sink, are they SCR? The location on the board? Thanks
 
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MaxHeadRoom

Joined Jul 18, 2013
23,908
MC-60:
Here is the schematic, the SCR's are the power devices that are switched by the MOC opto. The two rectifiers are part of the bridge.
D1, D2, Q1, Q2. all on the heatsink.
If Q1 or Q2 are shorted it will show the symptoms you have.
Max.
 

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Thread Starter

serkel

Joined Sep 8, 2014
10
Forgive me, but it says MC2100 on that schematic that was uploaded. Shouldn't be MC-60? In any case if I cant get MC60 to work I have a MC2100 to fall back on, that one I know works. I'll have to build a PWM, I bought all the parts to build one.

I also did get a High Power SCR Motor Speed Controller Voltage Regulator, and someone said
"that is a simple Triac with a bridge follower, quite a bit cruder than the MC60 or the KB style SCR bridge type.
Not a very good application for a DC spindle motor"
;), but would it be ok to use on 2x72 belt sander/grinder? I wont be using a the flywheel, I'll have a 3"wheel machined to replace the flywheel.
Ok off to check to see if D6 was blown. and Q1 or Q2, do they have to be remove from the board?
 

Thread Starter

serkel

Joined Sep 8, 2014
10
D6 was not blown, I had a small 2 pin connector cable that was attached to a motherboard to power a 80mm fan put a 1k resistor attached to small RS 12vdc PS kit set for 5vdc, put it across the pins of the LED and it lit, I was hoping that was the culprit.

As for the SCR bridge. Please explain why the SCR's can not be tested while still attached to the board?
Last week when I started this project to save this MC-60, I tested the entire bridge. I set my Fluke to diode mode.
1 - Q2 had no reading (it was replaced, now 511)
2 - D1 had a reading of 517
3 - D3 had zero reading (which was replaced, now it's 505)
4 - D2 has 517
5 - D12 is 511.
Should I put back the MOC?

What is my next step?
 
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