Author Topic: Mini Lathe Electrikery....... (Read 65515 times)

doubletop · « **Reply #25 on:** May 18, 2011, 06:31:16 AM »

To add my tupence to this I'd say the filter board arching is a symptom and not the cause of the problem. It certainly isn't going to make the motor go backwards at full speed. If a track is burnt through nothing will run, if C1 or C2 (the one on the live side) is shorted the mains fuse will go and then nothing will run. If C1 or C2 have failed open you'll only get noise on your TV.

If its the brushes then maybe its a back EMF that caused the spark on the filter board and has also progressively trashed the speed controller eventually leading to a catastrophic failure causing the motor to run backwards for a while and then it got totaled.

Look for similar arching on the speed controller, evidence of arching on the brushes and commutator. If you find problems fix them all otherwise you'll be back here.

Apologies if I've repeated what has been said before but my money is on the filter being a red herring.

Pete

John Rudd · « **Reply #26 on:** May 18, 2011, 07:29:30 AM »

Quote from: andyf on May 17, 2011, 07:07:56 PM

I have the circuit schematics and parts list which KB have now unsportingly removed from the manual, so if you need them, give me a shout.

Andy

I have the parts list and circuit archived if anyone else needs them, give me a shout.........

Dont by pass the board, connecting the motor direct to the mains!!! it is a dc motor with a permanent magnet field....Quite different to a drill motor...

lordedmond · « **Reply #27 on:** May 18, 2011, 10:28:44 AM »

John its not the controller board is just a mains filter to filter out the odd order harmonics generated by the switching pulse width controller , the controller board is bigger and has mosfets on it the board in question ha only passive parts on it a couple od c's and a choke

note the colour of the cables and number of them,, live ,neutral and earth no othe connections for speed pot emergency stop etc

Stuart

Stilldrillin · « **Reply #28 on:** May 18, 2011, 11:20:17 AM »

Well.... I fitted 3a fuse in plug. (I've got plenty)!

Couldn't find me 60watt test lamp. So, I just wired it together with junction block, and no blackened gubbins......

I switched on. Released emergency switch lock. Selected forward (probably). The motor spun up for 1 second. POP!

Plug fuse blown......

Hadn't seen a flash. So, I repeated with lights out. POP!

Flashed inside the motor.

So, I went out for a walk........

David D

Bluechip · « **Reply #29 on:** May 18, 2011, 12:19:56 PM »

Dave SD

If you can get it to me tomorrow, I'll have a look.

I have a Variac + Bridge rectifier so we can verify the motor itself.

Got dozens of fuses, so that's no problem.

Can you give a pic of the controller board, I have some S8020L SCR's from when mine did the 'phttts' on me. I think

If it's the one with SCR's ..

EDIT ................. YES, I HAVE 4 of the little blighters

Anyone know what MOSFETS are in t'other sort. Got loads of them too, just no idea what they are.

It may be I have a suitable substitute.

Dave BC

lordedmond · « **Reply #30 on:** May 18, 2011, 12:26:50 PM »

time to get a new motor then

A point before you spend

dis the motor from the control board and replace it with a 100 watt lamp BC or GS your choice make sure its a 220 volt one not 110 one( we used to have at Stanton Iron works 25 v, 50 v, 110 v and 240 volt lamps all in normal BC

) then try to power up you should be able to see the result of the speed pot in how bright the lamp is , if it goes full on or not on you need a new pcb ark euro do do spare ones , but beware duff motor could release the magic smoke for a new board and visa versa

may be useful http://www.repaircontrol.com/FinalTest/FCSeriesPreInstallation.pdf

http://www.repaircontrol.com

Stuart

Stilldrillin · « **Reply #31 on:** May 18, 2011, 12:36:49 PM »

Dave.
Is this what yer after?

Commutator looks a bit grotty. Seeing as it's only done 2 seconds work.......

Hmmm......
Stuart. I think this is where I hand over to a Higher Authority......

David D

Bluechip · « **Reply #32 on:** May 18, 2011, 12:44:20 PM »

Hi Dave

Seen worse comms ....

Any type numbers on the components screwed on th LH side ??

5 of them, metal tabs capscrewed onto the heatsink ??

Will be on the black bit under the screws ( M3 ??? )

Looks a bit like mine, not sure ??

Dave BC

lordedmond · « **Reply #33 on:** May 18, 2011, 01:04:51 PM »

David D no problems it take a real man to call for higher help

good luck with it Dave BC

If all else fails this may help http://www.amadeal.co.uk/acatalog/KB_Mini_Lathe_Speed_Controller_Circuit_Board.html
http://www.littlemachineshop.com/Reference/DriveTroubleshooting.pdf

John Swift · « **Reply #34 on:** May 18, 2011, 01:05:30 PM »

Hi Dave SD ,

the pictures are interesting

your lathe looks like this one :--- http://www.cnczone.com/forums/mini_lathe/125585-wiring_parts.html

the motor does not look too bad , as Dave BC said

one way to test it is to apply a low voltage AC across the commutator (with the armature out of the motor )

then measure the voltage between adjacent segments ,it should be all the same

a shorted turn or an open circuit will result a marked difference

If the problem is the control board

first check the 3 diodes and 2 thyristors (scr's) on the heatsink are not short circuit

and then 275V varistor MOV1 and the capacitor across it C20? , they are both directly across the mains supply

John

Stilldrillin · « **Reply #35 on:** May 18, 2011, 01:06:00 PM »

Dave.

Top three are numbered, D8010L

Bottom two are, A69108

Is this pic any help?

David D

Stilldrillin · « **Reply #36 on:** May 18, 2011, 01:10:34 PM »

John.
I appreciate you trying to educate me..... But!

Where do I get low voltage AC from?

The control board instructions are beyond me........

Seriously out of my depth now!

David D

Bluechip · « **Reply #37 on:** May 18, 2011, 01:49:13 PM »

Nearly same as mine, I have the bits ... dunno about the technology ???

@John

When the one on my WM16 was visited by blast, fire, pestilence and a general all-over immolation. The varistor, X-cap and the diodes were all intact.
They're still in there.

Both SCR's were s/cct, hence the aggro.

Just replaced those ..

@ Dave SD

Low voltage AC is the forte of a Variac ... Variable Transformer ...

I think that A69108 number was non-findable, maybe it's an in-house P/N ??

Dave BC

John Swift · « **Reply #38 on:** May 18, 2011, 01:54:35 PM »

Hi Dave ,

I assume you will be working with Dave BC

the safest way is with a step down transformer ,to limit the current to about 1/2 to 1A

to make the voltage between segments large enough to measure , about 0.2V

and not two bulbs connected to the mains as I did as an apprentice at Pilkinton's , about 1974 ( before H&S)

If the board is the problem we will need the circuit from Andyf

John

PS Dave bc just seen your post , yes they could be in house numbers

any component in the controlled bridge rectifier that goes short circuit will take the other one with it , sooner or later

even if only one looks faulty I'd change both

Bluechip · « **Reply #39 on:** May 18, 2011, 02:14:27 PM »

Hi John

I have I-limited DC anyway ... Trouble with Variacs, being Auto, never quite sure which may be the hot end.

No doubt would be fairly briskly enlightened with fingers poked in eh ??

Dave BC

John Swift · « **Reply #40 on:** May 18, 2011, 02:22:51 PM »

Hi Dave ,

the armature test is with a AC voltage to check for shorted turns , the transformer action of the armature windings

make them show up better than with DC

yes with a variac transformer you will need a step down / isolating transformer as well

John

lordedmond · « **Reply #41 on:** May 18, 2011, 02:32:14 PM »

we used to use a small transformer with the lams cut open normally called a growler from the noise it made when you found the shorted turn, did not work on the 100 plus hp dc motor I used to rewind though, as the turn was a loop of copper tape 1/2 X 3/32 the other name is not politically correct now a days

otherwise it was drop tested with 2 vdc from a mg set ( we used welder cable to carry the juice )

David D did you get my pm about the amadeal board being the same as yours

Stuart

Stilldrillin · « **Reply #42 on:** May 18, 2011, 02:37:30 PM »

Gottit Stewart.... Thanks!

Wish I'd got the vaguest idea what you lot were talking about........

David D

Bluechip · « **Reply #43 on:** May 18, 2011, 02:48:25 PM »

Maybe we shared a common tutor ???

Mine was Prof. Stanley Unwin ...

Dave BC

lordedmond · « **Reply #44 on:** May 18, 2011, 02:59:04 PM »

As part go my apprenticeship I had to spend a year in the armature/stator winding dept at Stanton and Staveley ltd at its Stanton works so it was big old dc stuff for me

john Swift just triggered a long lost memory from when I was 17 65 now though

so not so much as a unwind moment but trade talk

Stuart

andyf · « **Reply #45 on:** May 18, 2011, 03:15:12 PM »

Dave BC,

Got your message. The schematics should be in your email inbox by now.

Andy

John Swift · « **Reply #46 on:** May 18, 2011, 03:54:42 PM »

Hi Stuart

happy days !

I'm not sure how we survived the apprenticeship (your just 9 years older than me )

first weeks with the sparkes , worked on live mains circuits in a mixing room

sprayed trichloroethleyn at motors to degrease them ( and my hands!!!!)

all good fun that I expect todays trainees don't have today

later on followed my chosen career

worked in the drawing office on diagrams that I followed in R & D next door

to make part of the non contact measuring equipment to measure the thickness of the glass at the "UK5" float glass plant

a laser beam scanned across the glass

the reflection off the upper and lower surfaces was detected with a photo multiplier

then its just a matter of calculating the thickness

during this time at Cowley hill works ,had the fun of fixing the B&W cameras that looked into the glass furnace

they didn't work for long when the cooling water supply failed

for now we'll have to wait to see how the tests go on the motor and controller

John

Stilldrillin · « **Reply #47 on:** May 18, 2011, 04:04:10 PM »

Thank you all, for your input. It's very much appreciated!

Just arranged a visit to Dave Bluechip's, for Friday morning.

Then, we'll see what's what, possibly......

David D

Bluechip · « **Reply #48 on:** May 18, 2011, 04:54:28 PM »

Chin up lad .... as Wallace sez to Grommit ....

Look a bit positive ...

Friday 13th was last week ..... er ... I think it was anyway ...

Dave BC

lordedmond · « **Reply #49 on:** May 19, 2011, 02:50:52 AM »

John

yes live working was the norm then , trice for degreasing yep , dis boards with no cover on the live bit and at 550 vac

we used to clean the DC 220 vdc bus bars live bare hands

, open front slate switch panels and open frame rotary converters

later I spent the latter 30 years working for a bank looking after the engineering for the computer centre at Kegworth , retrained in diesel fitting , air control systems ,BAS and later BAS system programming

Now do nowt only play in WS as I need wheels to get

David D

going to Dave BC's by ek thou is gerrin a bit close , I will hey to get a thicker tin hat

Stuart

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Author Topic: Mini Lathe Electrikery....... (Read 65515 times)

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