[Shint]

About 1 month ago i bought a H.F. 7 x 10 minilathe, model 93212.

The thing isnt shabby for the price, i have no complaints except that it has been giving me some problems when i go to use it.

When i start it i make sure the speed is at 0, and the forward/reverse is at nuetral before powering up. Sometimes it will fire right up no hassle as soon as i select a direction and start turning the speed dial.

Sometimes i will turn it on and the indicator light shows power select a direction and when i turn the speed up nothing happens, no noise or change in the power illumination.

I've simply turned it off before and then back on and it worked fine, sometimes i have had to unplug it and then turn it on to drain out the caps on the board then shut it off and plug it in and works fine. A few times none of that has worked and so i just turned it on and checked it not running then returned speed to 0 and direction to nuetral but left it on and walked away for 5 minutes and it works. Sometimes i'll do all this but with no luck and just try it the next day and it works just fine.

Once i get the lathe to run, it wont give me any problems, i can change the direction from forward to nuetral and wont give me any trouble as long as i leave the power on.

So far it hasnt given me any trouble if i turn the power off and turn it back on sometime later that day. I only use the power switch when im not going to be using it for a while and use the for/nuetral/rev switch when im not going to be turning for a short while as i have read that using the power swich to much can damage the board from the innitial power surge over time.

It seems that it only gives me problems when it sits a day or so.

I've put the machine on a surge protector that has a on/off switch on it and use that to turn the main power on and off instead of using the machines on/off. And that was after it started giving me startup problems so i dont think its the cause.

I have checked the power switch/ directional switch and pot to see if there were any loose wires and verify them working properly with a dig, multi. They are all good. I haven't dug into the board to check for loose wires on it yet but think im going to after i post this.

Any help on this would be awesome, i have a sterling engine to finish

Thanks, Shint.

[Stirlingbuilder]

I don't have much help other that checking the board for bad solder connections etc. but you already have thought of that. It does sound like a bad cap on the motor possibly, you say the power light works and powering off and back on seems to effect it? I have heard of the HF lathes having cap trouble on the motors start caps, not the control board caps. I suppose it's possible for caps on the board to be bad too though. Look for buldged tops on the caps and any leakage when you inspect them. I am curious as to what type of Stirling your building though? (sorry, it's off topic)

[Shint]

Popped the cover, checked the board and everything seemed to be in order.
Didnt see any smoke stains or find any loose connections. If i understand correctly its a 110 DC motor that uses brushes and dont think there's caps on it,(but seeing as iv'e not delved that far into it to actually expose the motor i might be wrong about it not having caps).
I was talking about bleeding the power out of the caps on the board, so if it was some sort of logic chip error as i hadnt looked that far into the board at tha point to see if it even contained one bleeding the caps could clear the error.
Since getting a look at the board i dont think i seen a logic chip in there tho,,, just straight forward dc control.
Checked to see if the feed screw had been conveying chips into the box but the rubber seal seemed to be working good as it was clean inside.

I'm starting to think it might be easier to just build my own board and jettison the standard.

This particular stirling is my first stirling, just a basic alpha type to keep it simple. 15/32 inch pistons with a 1/2 inch stroke so its just a little feller. Iv'e salvaged some larger pistons from old nitro boat engines for a larger model. Once i get my lathe issues worked out and my boring bars in i ordered ill start working on the larger stirling.

[Stirlingbuilder]

I found some info that might be useful...
http://littlemachineshop.com/Referen...ngDiagrams.php
http://www.hossmachine.info/projects_3.html
Seems that a replacement may not be too expensive if you find the controller bad. I think you may also be right about the motor caps, I may be mistaken and they are on the 8X12 models insted.

Good luck

[Shint]

Cool, thank yah much sir.
Still wondering if it would be better, or cheaper to just make a controller.
Seeing as its just a brushed dc motor it wouldnt be to difficult, probably just pick the parts i dont allready have up from radio shack.
Hmm my controller is listed in there,,,but for allmost half the price of a new lathe. I'll give this post a few days in case someone happens to read and a light goes on and they're saying, oh yeah all yah have to do is this or that.

Like i was saying the lathe still works, just when it wants to, so i dont think its a bad pot, on/off, for/rev switch. It acts more like it has a loose wire or something cause once its running it'll go all day no problem, its just after it sits a while.

Well im gonna stroll thru the diagram of the thing and see i can track down the culprit.

Thanks again,

[Shint]

Interesting indeed, i have the last one on the list, fc250bj/110v.
I checked the ac going in at position 3-4=120 volts good good means the on/off is working properly, then was going to check for continuity across the pot, touched position 5 on the wire block then position 3 and there was a click( audible but not a pop), hmmm what was the click, turned the speed up and vroooom, its alive.

The wiring diagram i have that came with the machine is a bit different from the little machine shops diagram. On my diagram it shows a "wired" loop coming from position 3 past a link with the on/off switch then to a link that runs to the pot then thru a normally closed switch and then back into position 5, on the little machine shops diagram it shows the normally closed switch as part of the pot, looking in the power box the switch is on the pot.

Anyway now i have it narrowed down im gonna find some more info on the pot and see if its what is havin issues.

[Shint]

Ok checked my pot, the switch on the back is fragged. Its supposed to be nc when the speed is full counterclockwise and the switch is showing no continuity so its screwed. Checked to see if my local radioshack has a replacement 4.7k ohm switched pot, they dont.

Instead of paying out the 9 bucks and waiting for delivery of a new pot from L.M.S. i decided to try out a quick fix.

I ran jumpers from the wire block on the board that go to the pot switch ( on my model control board FC250BJ/110v, its the #3 and #5 position, #3 also hooks to the illum-on/off switch) i chucked a $1.50 momentary normally open pushbutton switch in between the jumpers.

So now when i start up the lathe i turn on the power(once ive made sure the speed=0 and for/rev is in nuetral) press the momentary switch i installed, choose a direction then set a speed. Problem fixed.

[Stirlingbuilder]

That's great, I thought you might be able to do something if you had a diagram to work with. Glad I was able to provide a small piece of help.

I haven't done an alpha type btw, let me know how it works out.

[WaveDude]

My MM Mini Mill has a similar though not as severe problem. Different board but proably the same type pot/switch. A lot of times the pot all the way off then back it'll work. Or if I cycle it a few times with the power off before using it, it'll work. I though it was a dirty pot but could be the switch. I'll file this away for later if I need it.