Mini lathe motor. Once again.....

[Stilldrillin]

It's now five years, since I had my last motor problems. Guess, I'm well overdue for a glitch. 

All has gone sweetly. Apart from a broken drive belt, and replacement potentiometer.

Until, a couple of weeks ago. When the chuck, just, stopped. Without my permission..... 

I checked the brushes. No problem, though I fitted a spare pair, to be sure.

There is power to the motor. For the first few seconds.... It will run. But, not happily..
 Then, there is no power, at the motor connector.

The control box, makes all the correct click/ plunk noises. When the control switches are turned.
 Wiggling wires, makes no difference. The motor will not run.

Trying again, next day. Just repeats the sequence. 

Should I swap the board? (I have a couple of spares).

A few thoughts, from the forum's Electronic Wizards, would be much appreciated...... 

[Pete49]

David my thought as you have extra boards is to change the board and if it runs well then it was the board and problem solved. If not then the hair pulling starts.
Pete

[John Rudd]

Disconnect the motor.......replace it with a 100w bulb....does the bulb brightness vary via the pot?

[Stilldrillin]

My thoughts too, Pete!
 But. It is better, I am guided by someone who has an idea of what I need to do....... 


Hello John! I'm pleased you're here..... 

I had forgotten the 100w bulb test! 
 But the assembly, was right where I left it. After the last fiasco.

The bulb does not light, at all...... 

[Brass_Machine]

I feel for you David. I am in the same boat now... I think my issue is the pot though.

[Stilldrillin]

Hello, Eric!

I fitted a new pot, early this year. Very easy to do. And, much better speed control, afterwards.
 The only problem.... The locating hole, in the control box, is much too large.
I glued the pot in place. With silicone sealer..... 

[Brass_Machine]

I had to do some turning, luckily, the controller I built for the CNC mill worked as a stand in. Finding the pot is a pita!

[Stilldrillin]

Finding the pot is a pita!

The speed control? How so? 

Or..... Do you mean, locating, a new pot?

[John Rudd]

Could you post a picture of your speed control board or its part/model number?

It could be either a Sieg or a KB or summat else....

No blown fuses? No loose wires.....?

[Stilldrillin]

Is this what you're needing, John?




No blown fuses. No pops/ bangs/ magic smoke...
 The very gentle, facing cut, finished. And, the chuck spun to a standstill..... 
Which was why, I thought it was a brush problem.

Checking, with the light bulb. This afternoon. The "usual", initial few seconds of power, didn't happen...

[John Rudd]

Thats a KB controller.....

You got a multimeter/dvm and know how to use it?

First check is to see if you got 12v at the brass pad marked 12v on the board, just above P3...
Connect your meter neg lead to the spade lug marked I1....I'm sure that is the reference point for voltage measurements.....
Else you could check that the big resistor R17 reads about 10-15k ( power off!!!) on your meters ohms range (20k)

[Stilldrillin]

John.
 I checked, between the 12v brass pad, and P1.....




Initial reading was around 35v.... Steadily reducing to around 7v.....
 Then, after some 20sec, to zero......



I next checked, the big grey, blobbed, lump. Power off. (Thank You!).....




A reading of, 18k. As best I can tell, on my meter......

[John Rudd]

No.....no...no...
You need 12v between the 12v pad and I1...

[Stilldrillin]

No.....no...no...
You need 12v between the 12v pad and I1...

Oh! Ermm? .... Ah! ...  I can, now, see I1 in the pic. Why couldn't I see it, on the board??   

So sorry, John.

An initial, higher reading. Dropped to a steady 4v. Only.....   

[Brass_Machine]

Finding the pot is a pita!

The speed control? How so? 

Or..... Do you mean, locating, a new pot?

Locating a new one....

[John Rudd]

David,
Can you disconnect the speed pot from P1,2&3 and re measure please?
Then measure the voltage at the ends of R17 ( the big grey resistor) with the meter negative lead still connected to I1...

I am expecting to see 12v at the 12v pad, around 22v at the end of R17 ( the end nearest the board edge) and a much higher voltage the other end....

Meanwhile if you have a good working board, swap it out for the faulty one to get you going....

[Stilldrillin]

No problem, over here, Eric......  http://www.amadeal.co.uk/acatalog/Potentiometer-AMA_SP_CJ18_157.html#SID=189

If you don't want to order, yourself. I'd be happy to post one to you..... 

[Stilldrillin]

John.

1, 2, 3 disconnected.  Initial, 'kick'. Dropping to 2v.....

Outer end of R17..... 2v.
Inner end..... 500v.  ? 

I've located the spare board.
 Deemed, a good 'un. By Dave Bluechip. Several years ago......

[John Rudd]

David,
My apologies, could you conduct the tests again,

But this time with meter black lead connected to F- on the board.....

Think I need to look for the board schematic after this, its hidden away somewhere in my manuals.....

Let me know how you get on....

Oh, one more thing, can you check the horsepower resistor? On ohms it should read zero-ish and is plugged in proper like....

[Stilldrillin]

No problem, John! 

Pad to F-. 1, 2, 3 disconnected..... Initial, 19v. Increasing, to 26v.

R17..... Outer, 50v.... Inner, 500v


Pad to F-. 1, 2, 3 connected..... 28v.

H/P resistor. 9 ohms. Properly plugged.


The replacement board.
 The original one, from the initial, Chester Conquest lathe.




Repaired, 2012......




Well..... The Stilldrillin Engine Orphanage, pre-Christmas party, is now, in full swing. Time to close the shop door, for a couple of days.....

Wishing, a HAPPY CHRISTMAS, to all Modders......

[Stilldrillin]

I managed an hour, this afternoon.....

Photographed, all, of the existing connections.  Then, removed the original board, and replaced with, the replacement.

Out to the shop. The light bulb test went, perfectly.
 
Connected to motor. It ran well, at all revs. Sounded a little rachety. Probably, due to the re-faced brushes, bedding in.

It wanted to creep, slightly, at slowest position. Before actually clicking, off... So, I tweaked the MIN pot, slightly.

I mostly use a 5" chuck. So, turned the ACCEL pot, 1/2 a turn, to give some 3secs acceleration time.

The only drawback. (So far)... It doesn't seem to have any braking effort. The unloaded motor spins to a gentle standstill.
 Is there anything, I can tweak? 


The incoming weather, and family needs. Will keep me indoors, until the New Year.
 Only then can I rebuild, and fully test run...... 

Happy, little Drillin. 

[John Rudd]

David,
If you let me have your email address I can send you the KB manual that has all the setup info in it....
It goes through the process of setting min/max speed, acceleration setting, current limiting etc.

[Stilldrillin]

Sorted nicely, John. Thank you! 

I managed an hour, this morning. The lathe is up and running. 

No time. (Or weather), for a full workout.
 Though, a piece of 12mm dia, rust. Was reduced to 10mm dia. As efficiently as expected......

Oh....HAPPY DAY!!   

[Stilldrillin]

Well..... Old age and winter weather, are keeping me from any form of shop project work.

But. I have managed several little bits n bobs. And, the lathe has performed, perfectly. 


The question, now... Does anyone run a repair service, for these boards?
 I have this duff one, and a doubtful one, in another control box.

[John Rudd]

Well....me of course..I  can repair them and have done more than several...

If you want to pursue contact me via email/pm...only too glad to help.