speed control pcb for Clarke CL300 lathe

[john swift 1Participant @johnswift1]

Hi Daryl ,

 

they don’t make it easy

 

with gears B & C out of the way and the two M6 screws removed

 

the die cast cover can be removed with the timbler assembly and gear A in place

 

the problem is you have to remove / move  the control box to adjust the belt tension

 

the wires should be long enough to leave them connected

 

if your like me it will take a few attempts to get it right

 

the grub screws only give you a small amount of adjustment

 

they push on the motor body

 

adjusting one screw in and the other out the motor is moved up and down a small amount

 

the grub screws are just visible above and below the lead screw

 

(the two studs holding the motor in place  are hidden behind the lead screw)

 

 

 

    John

Edited By john swift 1 on 09/12/2010 22:32:58

Edited By john swift 1 on 09/12/2010 22:45:33

[Daryl HeasmanParticipant @darylheasman56468]

Many thanks John ,there does not seem to be anything in the manual about it

 

regards

 

Daryl

[Ian S CParticipant @iansc]

Daryl,is it posible that you could replace the belt with a link type belt, if so it will save a lot of naughty words, and skinned knuckles, and quite a bit of time, might be a bit more expensive but will out last a V belt.  Ian S C

[john swift 1Participant @johnswift1]

Hi  Daryl and Ian

 

found this link with more pictures of motor and belt alignment

 

http://www.mini-lathe.com/Mini_lathe/Tuning/tuning.htm#Belt_align

 

 John

[William SmilesParticipant @williamsmiles10916]

Hi John,

 

I have just received all the components and built up the control box. Your advice was invaluable. Tried the box today, but it looks like there may be a motor problem as you indicated in one of your earlier post. The motor starts to turn but sounds as though it is catching on something. On further investigation there was a strong smell from the motor and smoke from the brush end of the motor. I disassembled the motor and found that the brushes appeared to be arcing on the commutator. They were black in parts with signs of carbon. I cleaned these and replaced the brushes, but still the same. Looks like a new motor. Any advice? If a new motor where is the cheapest to buy. I thought I found a supplier at £60 + VAT but now cannot find it.

 

Thanks,

 

Bill.

Edited By William Smiles on 06/01/2011 17:50:03

[john swift 1Participant @johnswift1]

Hi Bill ,

 

you could have done without that

 

if you disassemble the motor you are likely to see two things

 

1,     one of the windings overheated and burnt looking

 

2,     the gap between the segments of the commutator wider and burnt

        where the brushes run

 

there should be almost zero voltage between the segments shorted by the brushes

as they  move from one to another , but this is not so with a faulty armature

 

 

I almost directed you to the wrong motor

at some time I have seen the CL300M identified as a C3 minilathe

 

but having a look at the C3 motor at arceurotrade

the motor is listed as item C3-150   350w   £65 inc VAT

 with a note to check its the one for your lathe !

 

the C2 motor is not listed but its worth giving them a call  to check  its the one you need and price

 

    John

[William SmilesParticipant @williamsmiles10916]

Hi John,

 

Actually I found your earlier post and had already ordered the C3 from arceurtrade at £65. When I said I had seen one earlier and could not find it, this was the one I had seen. Are you saying that this is the wrong motor? It seems to be right from the photograph and description, but I do believe that the original motor was only 300 watt! and this is 350 Watt. I have emailed arceurtrade to question whether this is the correct motor, but it may be too late to stop the order. If the unit is the same size, has the same fittings and has all the same specifications other than the 300 watt I can see no real problem, or am I been naive? It certainly is a good price at £65.00 delivered, as the same unit from Machine Mart is £130.00.

 

Best wishes,

 

Bill.

[john swift 1Participant @johnswift1]

Hi Bill ,

 

I need to double check

 

looking on the little machine shop spares there is a 250 W and 350 W motor

for the C2 and C3 lathes I can’t find details of the phyical size

 

the FC250J controller is for a 250W motor but my lathe has a 300W motor

labled 300W  2A  220V – 240V   5000rpm

unless i’m missing some thing the numbers don’t add up

 

300/220 = 1.36A

 

 

I can not measure the physical size of my motor just now to see if the

350W motor from arc euro trading will fit

 

on the face of it  the 350W motor should overload the controller

if the motor is realy 350W  and you load it to the maximum taking heavy cuts

 

 

 John

 

 

 

[William SmilesParticipant @williamsmiles10916]

Hi John,

 

I have just taken the motor off my machine and compared the specifications to the arc euro. It is very different and will not fit. I have also received an email from Arc euro confirming the same. Fortunately it was in time to stop delivery. Looks like I am back to Machine Mart and their £130 version. I am still waiting for some information from Little Machine Shop and Chester Machine Tools on their Motors specifications, which may be a little cheaper (but not much). Certainly turn out to be an expensive machine (could have bought a new one with what I have paid out).

 

Thanks for your continuing support,

 

Bill.

[john swift 1Participant @johnswift1]

Hi Bill

 

I’m just glad you didn’t end up with the  wrong motor

 

 John

[flintlockand steelParticipant @flintlockandsteel]

Hi

Not sure if this follows on exactly but I have a CL300m variable speed, except it’s not.

It’s either all or nowt. I was suspecting the pot but skimming the replies here, could it be the board?

I haven’t taken it out so I don’t know what number it is but it has large components standing off and a couple of large square yellow things to the left. Heat sink top.

I’d just like to swap it and get the machine running again asap.

Any ideas?

[john swift 1Participant @johnswift1]

Hi Jon ,

 

I assume your board looks like this

 

the two yellow relays on the left , near the terminals
form part of the interlock circuit that forces you to start at minimum speed

 

one of the common faults is the two FET’s ( on the heatsink on the right )

go short circuit and the motor runs at full speed

 

 

with the mains supply disconnected

 

if you measure the resistance between the gate and source terminals on each FET

you should be 50k (50,000 ohms)(outer 2 terminals)

 

between the drain and source should be virtually open circuit –

more than 20 M ohm (20,000,000 ohms)

 

even with a faulty speed control potemtiometer ,

the maximum speed in reverse should be about half the forward speed

 

the speed control is special 5k linear potentiometer plus a single pole switch

that you have to buy form the likes of machine mart , arc euro trading etc.

 

while it looks like the on/off and volume control on a radio

the potentiometer is linear not logarithmic and the switch is closed when fully anticlock wise

not open !

 

a new board from machinemart will be quick , but expensive

if in stock arc euro trade for example will be less expensive

 

if you decide to replace the FET’s your self

you can use two 2SK790 , IRFP450 or STW20NK50Z FET’s

 

either from RS components . Rapid online etc or ebay

 

John

 

Edited By john swift 1 on 03/02/2011 00:05:55

[William SmilesParticipant @williamsmiles10916]

Hi John,

 

Just thought I ought to let you know that the lathe is now up and running (at long last). The motor was the last component that had a fault and I eventually had to buy one at Clarkes at a cost of £130. It might be of interest to someone that I rang round quite a few places to see whether it would be cheaper to have it repaired and the general concensus was that it would cost more than the £130 to buy a new one. It eventually cost me more to put it right than buying a new CL300m and I could have bought a similar machine at £350 brand new. Well it is always easy to say in hind sight. Anyway I have learnt a lot and now have a working lathe. I would just like to repeat my thank for all your advice and efforts as I would have not been able to do it without you. I might neeed your advice again in the future but I hope to get a little bit of use out of the lathe first. By the way, again for the edification of others, I have fitted mine with a 2 Amp quick blow fuse in the control box carrier and 5 amp in the plug and it seems to cope adequately with the load (the replacement motor is a 250w and not the original 300w). Would rather spend a few quid on fuses than keep having to replace components on the board. It might help a few people.

 

Thanks again.

 

Best wishes,

 

Bill

Edited By William Smiles on 03/02/2011 12:16:09

Edited By William Smiles on 03/02/2011 12:18:32

[Pat BraveryParticipant @patbravery]

Hello William, Good to know that you are up and running, you will find that the new fuses that you have fitted are the ones recommended to fit by Clarke, did you have higher value ones fitted as that could have caused the damage, best regards Pat

[john swift 1Participant @johnswift1]

Hi Bill ,

Good to know you have a working machine

 

how easy do you find to part off ?

 

I found it difficult at first , until I fitted the brass gibs from Arc euro trade

the originals looked a little miss shaped

( If I had a miller and some brass I could have made my own )

 

 

 

John

 

 

[flintlockand steelParticipant @flintlockandsteel]

Hi John

My board looks like a little different to the one you show, the heat sink is at the top. I’ll post an image later on from which you may be able to determine age or other relevant specifics.

 

Jon

[flintlockand steelParticipant @flintlockandsteel]

This is the board my 300 has

Note that the old fuse carrier has been replaced.

[William SmilesParticipant @williamsmiles10916]

Hi John,

 

In reply to your question I do not know as I have not tried it yet, but if you found it difficult I am sure I will too. Maybe you can show a picture of the brass gibs from Arc euro trade. I have a milling machine which I made when I was about 21 and so should be able to make the parts. Keep up the good work.

 

Best wishes,

 

Bill

[flintlockand steelParticipant @flintlockandsteel]

Having now got the board out and tested I find 1 appears to be open circuit i.e. the reading just falls away to 0. The other reasd .2 on the 200k scale (digital meter). I was once a PCB draftsman but never fathomed the logic of operational circuits so hope I’m setting and reading this meter correctly

[flintlockand steelParticipant @flintlockandsteel]

Is there anything to choose between these components?

I looked at RS and didn’t see the 2SK790 ,

The IRFP450 were £3.34 each and the STW20NK50Z £1.99 each.

How often does this fault occur? I’m just wondering if it’s worth getting a second set.

Finally the replacement fuse holder is inside the box, and inaccessable for a quick change if it pops. What’s the name for the style of holder normally employed and the fuse rating?

 

Many thanks

Jon

[john swift 1Participant @johnswift1]

Hi Jon

your controller is like mine !

 

looking at your picture

I it looks like the FET’s have been changed at some time as well as the resistors R4 to R7

(R4 & R5 = 100k , R6 & R7 = 100 ohm )

plus R42 ( 220 ohms ) in the snubber circuit – replaced by the two green wire wound resistors in your picture

0.2 on the 200K range = 200 ohms, this could be the 200 ohms you measured if C2 is short circuit.

 

the source and drain leads on the FET’s are connected together and should be

high resistance

( depending on the resistance range your using you may see C2 charging )

 

I’ll upload some pictures

 

John

 

ps

on my board I replaced a link with a 1N 4148 diode and 12K,resistor

and added a 47uF acpacitor , to make it like the later versions

this limits the rate of speed increase

if you rapidly turn the speed to maximum

Edited By john swift 1 on 04/02/2011 21:01:27

Edited By john swift 1 on 04/02/2011 21:04:52

[john swift 1Participant @johnswift1]

missing picture

[john swift 1Participant @johnswift1]

Hi Bill ,

 

the gibs are 150 and 118 mm long and possibly made from 10mm x 6mm stock

the original gibs are slotted where the grub screws are , this is a weak point

the new gibs don’t have the slots and are gripped by new grub screws with sharp points

 

with the brass gibs the slides moved more smoothly even when tightened more

than the originals ones , 

 

  
John

Edited By john swift 1 on 04/02/2011 22:42:18

[john swift 1Participant @johnswift1]

Hi Bill,

 

pictures of top slide gib in position

the new gib is a better fit than the original !

[john swift 1Participant @johnswift1]

Hi Jon ,

 

I forgot to add

 

the 2sk790 is the FET originally fitted on my board 10 years ago

 

both of the other FET’s OK but as the newer stw20nk50z has the lowest on resistance and is cheaper thats the one I’d use

 

the FET’s tend to fail when the motor is stalled or fails its self

the correct fuses help

and the mod on the later surface mount versions that limit the rate you can increase the speed

 

this is the mod on my old board
the 12k resistor and diode is fitted in place of a link

that looks like a resistor with just one black band

 

 

John

Edited By john swift 1 on 04/02/2011 23:52:33

Edited By john swift 1 on 04/02/2011 23:55:53

Edited By john swift 1 on 05/02/2011 00:06:34

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