Help me Comprehend my MC-60 Controller

[SteveHGraham]

These responses are great.

It turns out I don't have a spare 5K pot, so I'm going to have to buy one.

The motor has fan blades on a cast iron wheel which must also be a flywheel. It's really heavy. I feel like I should make a light replacement from aluminum. I also have to figure out how to put a V-belt on the motor. The shaft is threaded, so I can't just slide one on. I guess I could turn the exposed part of the shaft round, add a flat, and use a setscrew to secure a pulley.

Now if only I had some tooling so I could use my new press to make a box for the controller...

[SteveHGraham]

Or I could machine a belt groove into the existing cast iron wheel? Definitely faster. There is enough meat there to permit it.

Now I'm thinking I should get a flat belt and make a crowned pulley to attach to the sander. That way I could leave the motor alone. The flywheel does not appear to be crowned.

[chucketn]

I used my 4x6 bandsaw to remove the hub part of a flywheel like you are talking about. It has the LEFT hand threads to screw onto the motor. I turned a v grove in that part and
put it back. My X2 came with a belt drive. I did have to make taller spacers to get the motor to line up with the spindle pulley. I didn't bother with 2 grooves in the motor pulley, as I don't use speeds above 2500 rpm, which I get easily from my setup. I don't have a need to run the mill in reverse either.
I also happened on a box of 5 1/2" x 13 tpi LEFT Hand Dormer Taps on ebay in case I needed to make a custom pulley it ot for the several treadmill motors I've collected. If you decide to make a custom pulley I could provide you with one.

Chuck

[WJH]

Just go down to your local Radio Shack.. Oh... Wait, never mind, better go to Digikey...

[SteveHGraham]

Just go down to your local Radio Shack.. Oh... Wait, never mind, better go to Digikey...

You had to bring that up. I kept that place in business when I was building current and temperature controllers at the university, for one of my physics professors. Later I supported them by buying lots of stuff for the guitar amps I made. Then the miserable traitors just up and ABANDONED me! The one near the university is gone, without even a kiss goodbye. I'm going to have to drive to the Little Havana Radio Shack or the big electronics supermarket on 36th Street from now on.

I guess I'm still in the anger stage of grief.

[tornitore45]

Digikey is a good source, is the ENCO and McMaster of the electronic trade.
If you can plan ahead they have everything. Screw Radio Shack or even Fry with their bubble pack $1.89 single small capacitor.

[SteveHGraham]

I always use Mouser.

When I was a Physics TA living in poverty, I bought a new motherboard. I installed it in my PC, and I heard a sound like bacon frying. Something had shorted against the case.

I opened it up and saw what appeared to be a fried resistor. I got on the phone with Mouser, and we spent half an hour trying to figure out what it was.

I finally realized it was an inductor. I had had two electronics courses, but we had never used inductors that looked like resistors.

Mouser sent me the part. The cost was like 20 cents.

After that, I will always go to them before any other electronics vendor!

[WJH]

Radio shack was a rip off on most everything, except for Arduino Shields from Seeedstudio... Go figure!
I used radioshack for when I needed a part right now! When I fixed my DRO and wanted to convert my old scales to DB9 connectors, I couldn't... I left for a trip, and my first day on the trip I had ordered the DB9's from E-bay... After the 5 day trip, and I was home, no connectors!!! I was fuming! And Radioshack had just gone out of business... So I ordered them from Digikey... I now have both orders at home, and I go home tomorrow. Needless to say, I took my good serial cable I used with my Atmel programming board and cut it up. I spliced it into one of my old scales and hooked it up to my new DRO to test my wiring. It worked, but I sacrificed my serial cable!
When I start something, I have to finish it. It's a psychological thing with me. Loved ones who want to spend time with me get labeled as enemies, schedules get sworn at, and I get deep tunnel vision... However I still leave to go to work... For another 5 freaking days... I am like a rabid animal when I get home, I need to finish what I started. Well some stuff, like a live steam locomotive which takes years, I don't have that problem with. Go figure..
Anyhow, thats where Radio Shack came in, allowed me to run to the store to get the part so I won't have to wait until I visit home again. No more radio shack is a major inconvenience!
When I lived in San Francisco, I would just drive to Berkeley to that one electronic shop thats been there for 40+ years.. Al's something? Can't remember...
Funny you mention 36th street... I used to live in Miami Springs when I was doing my private pilots license, and also going to MDC for the air traffic control program,

[SteveHGraham]

If Radio Shack were still here, an overpriced pot would look pretty good compared to the same pot, cheap, plus $5.00 in postage and five days of waiting.

[SteveHGraham]

I ordered some 5K pots, but it turned out I had one on hand, so I installed it. I connected it to the board, and I connected the motor and also an AC cord (hot and neutral only).

I tried to get the thing to work, but it does not generate voltage at the DC outputs. It just blows the circuit breaker.

While I was working on connections, I went to an electronics forum and asked if it was okay to ground the chassis, and they said it was fine. I did not make a connection, but it is possible the bare braided connector on the power cord touched the chassis when I turned the unit on. I have not seen sparks or smoke, and the LEDs light up.

I have read that you have to create a common ground for the AC input and the low end of the 5K control pot. I do not see anything on the board that looks like a convenient grounding spot, but I suppose I can slap something together.

Help would be appreciated. This MC-60 could just be a lemon, but I want to give it a chance.

[SteveHGraham]

I checked the resistance between the DC outputs, and it's zero. That's with no motor and no AC connected.

[SteveHGraham]

I thought this thing had five transistors mounted on the chassis. It turns out they're thyristors. As I understand it, they are rectifiers that supply a lot of juice, but they are not conventional diodes.

I suspect I fried them when the ground on the power cord touched the chassis.

They have three leads. As you look at the component from the front, leads down, they go cathode, anode, and gate, from left to right. A fried thyristor will have a short between the cathode and gate. That's what I have in four of five thyristors.

They are cheap, so if I can find them locally, I can have this thing fixed by tomorrow, for around ten bucks. That's assuming I didn't destroy anything else, but since the thyristors are so sensitive, I have high hopes that they shielded everything else.

This is what I get for listening to Internet experts.

Someone correct me if I'm wrong, but please, no experts.