Mill X Feed Boo Boo Mea Culpa!

[Martin King 2Participant @martinking2]

Electrical fault on X Feed PCB?

[Martin King 2Participant @martinking2]

Hi All,

I realy should not be allowed near anything electrical!

I have a power X axis feed on my Warco 18 Mill which I got in a clearance from Axminster a while ago, made the bracket etc and installed it. Worked just fine and tranformed the machine into something a pleasure to use.

I did not need and did not fit the Limit Switch unit and just coiled it out of the way.

After a while there was an intermittent fault where the feed would only work one way and not the other. This turned out to be a dry joint in the limit switch box which was fixed by giving it a 'wiggle'. Worked for ages after that.

I removed the small switch buttons to stop them accidentally getting knocked.

Yesterday I was using the mill all morning just fine, then dropped something and jarred the limit switch which brought the fault back so thought I would fix it once and for all and resolder the joint properly.

STUPIDLY I did this wihile the mill was still connected to the mains! Small puff of smoke from the joint , fuse in unit blown, me VERY angry.

Changed the fuse but now nothing works at all on the feed unit.

Have tried the limit switches in all possible positions but no go.

The board is marked SIEG MACHINE and does not appear to have any black or sooty spots on the front, have not looked at the back as noit easy to get to.

HELP NEEDED please!

I think the unit is now discontinued but I know SIEG is still around.

Regards,

Martin

[Les Jones 1Participant @lesjones1]

Hi Martin,
If you can find the model number on the feed unit or in it's manual and track down a schematic for it on the web we MAY be able to suggest what component has been damaged. Other than that you will need someone with electrical knowledge who can look at it (And possibly remove it and work on it in there workshop.). As you give no idea of your current location in your profile then members of the forum would not know if they lived near enough to offer help.

Les.

[Clive FosterParticipant @clivefoster55965]

Looks to be a fairly basic DC motor variable speed drive board with integrated switch mode power supply. If worst comes to worst functional replacements can be found not too expensive although you may have to accept a separate power supply and do some case mods to fit. Just need the motor data to match board to motor.

That said I'm surprised that being plugged in whilst you soldered popped a component. Normally limit switches and the other controls would be on the driver side downstream of the power supply and thus isolated from any mains connections. Good practice is to make anything involving limit switches robust and short circuit proof in case stuff gets in. UM, you did turn it off first didn't you?

Clive.

[Russell EberhardtParticipant @russelleberhardt48058]

The big resistor in the middle of the board looks rather cooked I would check that but the most vulnerable part is probably the little transistor next to the connector for the limit switches. Do you have the ability to check it?

Russell

[John RuddParticipant @johnrudd16576]

Les, looking at the components and the layout, I'd say the controller is probably based on the later XM series of speed controllers…..the clue I think is the small toroidal transformer adjacent to what I think are the thyristors….the big 6A diodes forming a full wave bridge with the scr's…..the design is based on the KB series of controllers

Ah, just seen the label on the board, it is an XMT 2315…..

@ Martin If there are no visible signs of blown components, then I'd be looking at blown copper track….weakest link and all that….then start cold testing

 

 

Any thoughts Les?

Edited By John Rudd on 20/11/2016 11:41:36

[John RuddParticipant @johnrudd16576]

I've just looked on Arc's website and Ketan is listing spare boards for £88…..

http://www.arceurotrade.co.uk/Catalogue/Machine-Spares/SX1-Spares/SX1-121B-Main-Control-Board-XMT2315230v

[maurice bennieParticipant @mauricebennie99556]

Hi Martin ,Have you checked the mains and plug fuses ?

[John RuddParticipant @johnrudd16576]

Martin,

I have a schematic for the KB boards, the component references will be different, but at least you wont be working totally blind….

Les has a schematic which he drew out,( again the Sieg boards used the orig KB desing) the later XM boards used on the X3 mill, again the schematic will help even if the component designations differ…..

[Les Jones 1Participant @lesjones1]

Hi John,
I agree that it is probably one of the standard controller boards. I do not think it will be a modified board designed specially fo a power feed so I don't think Clive's comment about the limit switches being on a low level isolated supply is valid in this case. I think the limit switces will be connected directly to the output of the reversing switch so the output will have beed shorted to earth via the soldering iron. I am reluctant to suggest doing much testing as Martin does not seem to have respect for the dangers of mains electricity. I would not attempt to solder to a circuit at mains voltage.

Les.

[John RuddParticipant @johnrudd16576]

Posted by Clive Foster on 20/11/2016 11:14:09:

That said I'm surprised that being plugged in whilst you soldered popped a component. Normally limit switches and the other controls would be on the driver side downstream of the power supply and thus isolated from any mains connections. Good practice is to make anything involving limit switches robust and short circuit proof in case stuff gets in. UM, you did turn it off first didn't you?

Clive.

The two scr's and two of the the big diodes form a full wave bridge rectifier circuit…..The 0v rail on circuits like these are actually at half mains voltage wrt earth….so connecting an earthed soldering iron is likely to pop some thing…..

I speak from experience….

[Les Jones 1Participant @lesjones1]

Hi Martin,
There are two questions that we should have asked. 1 Has the new fuse that you fitted also blown ? 2 Have you checked the fuse in the plug and thet there is power at the socket ? (Shorting the mains to earth if the circuit is fed via an RCD would trip the RCD. It may also have tripped the MCB depending on how high the fault current was.

Les.

[Martin King 2Participant @martinking2]

Hi Les,

"Martin does not seem to have respect for the dangers of mains electricity."

Not lack of respect but shear forgetfullness and stupidity, in a hurry to get on etc, hence in thread title Mea Culpa. My location is South Dorset

Mains plug fuse OK and replacement fuse all OK.

Russell: I do not have the skill to check this sort of thing and clearly a little knowledge is dangerous. Way out of my depth here!

Would anyone be interested in me sending them the board to look at and I would be happy to pay for any repairs and time and postage etc?

Regards,

Martin

[Martin King 2Participant @martinking2]

I will remove the board tomorrow and post pic of the back side

[John RuddParticipant @johnrudd16576]

Martin, check your pm box

[Martin WParticipant @martinw]

Martin

When you tried the unit after replacing the fuse did any of the lamps on the front panel light. While it is not really helpful Aussee Machine tools have a spare board priced at about $146.

Martin

[Martin King 2Participant @martinking2]

John R, PM sent

[Les Jones 1Participant @lesjones1]

Hi Martin,
Before removing the board it might be worth doing a few tests without mains power connected. Here are the reasons for my suspicions. SCRs and diodes normally fail short circuited. (Unless there is a very large current available to blow them open circuit after they have initially failed short circuit.) As the new fuse that you fitted has not blown I don't think the SCRs or diodes have failed. I suspect that the power light is a neon bulb connected directly across the mains and probably after the fuse holder. I can find no pictures of the board where I can read the labels next to the connectors so I have no way to know which wires go where. Could you post pictures that show the labels next to the connectors and pictures taken from a little further away so I can see where the wires go. I want to try to get you to test for continuity between the 13 amp plug and the mains input to the board.

Les.

Edited By Les Jones 1 on 21/11/2016 09:21:26

[Martin King 2Participant @martinking2]

Marti W – no lights at ll when powered up.

Have taken some more pics as requested, many thanks to all for helping me out here,

Paul L in Australia has kindly sent me some manuals and wiring diagrams, looks like Finnish to me

These show the small labels, I have turned them round the best I can.

Wider shot as requested, tried to move some of the wires to make it clearer.

ditto

back of board, no damage that I can see?

Martin

[I.M. OUTAHEREParticipant @i-m-outahere]

R35 appears to be missing ( bottom photo , bottom left edge – 5th component from left ) although it may have not been used in the circuit you need to look at the the schematic to find out .

[Les Jones 1Participant @lesjones1]

Another forum member has kindly provided martin with a PDF of the Grizzly H8178 table feed which looks to be the same unit as Martin's. (This is a link to this manual) If Martin's unit wired in the same way as the diagram on page 21 of the Grizzly manual then the power light should be on no matter what the fault is on the controller board. (Is should be on even if the fuse has blown.) We need to get Martin to check the wiring from the 13 Amp plug to the unit to investigate this first. The bad news from this diagram is that the limit switches are not connected between the reversing switch and the motor as I had suspected. (If this had been the case then two diodes and two SCR may have been damaged that would be easy to replace.) It is connected (via a set of changeover contacts on the reversing switch) to the control input on the board that would be connected to the interlock switches when the board is used in a lathe. Looking at the last of Martins pictures posted at 16:55 on Nov. 21 it looks similar to the speed controller used on the X3 mill. Both use a dual and a quad op amp and both use phase angle control with an SCR half bridge. You can compare the pictures of Martins board with the pictures on my website of the board from my X3. This page includes the schematic I traced out of the X3 board. I think it is a reasonable assumption that Martin's board will be very similar. If so connecting mains earth (Which will be at almost the same potential as mains neutral.) will have injected – 300 volt pulses into the low power electronics every half cycle when live was positive with respect to neutral. I think this is likely to have destroyed a reasonable number of components which may make repair of the board uneconomic. If it is the same as the X3 board which is coated in a thick varnish it will make it difficult to replace SMD components. It would probably also be necessary to trace out the schematic of the board first to aid logical fault finding.

Les

[John RuddParticipant @johnrudd16576]

R35 would normally be connected across Q4, subject to Les's schematic being correct,  which is the fault light latch….closer examination of the board will tell if it has been 'blown away' or just not fitted….

And just to clear up any misunderstanding on the board and X3 mills….this is not the same board fitted to later X3 mills with the brushless motor….

Edited By John Rudd on 22/11/2016 09:46:47

[Les Jones 1Participant @lesjones1]

Hi John,
I was wondering about the same thing but I think the component numbers are different to those used on the X3 board. You can see that the components around the fault circuit in the schematic are placed close together on the X3 board. (The picture of the etch side of the X3 board was taken by placing the board on a flat bed scanner.) It would be nice if the missing R34 acted as a fuse and prevented too many other components to be destroyed. I think I will add your comment about the difference between the X3 and SX3 to my website.

Les.

[Martin WParticipant @martinw]

Hi

The fact that none of the lamps lit when Martin applied power to the unit implies that there was no mains getting to the unit, one item Les wanted Martin to check. Looking at the pictures Martin posted there 'appears' to be no damaged components or tracks, unless R35 has vanished into oblivion. While I realise that it is a low power device I was wondering if the 22V zener might have afforded any protection to the components downstream before the fuse blew. Looking at the pictures it doesn't look as if it suffered catastrophic failure as could happen with a mains short, though a fast acting fuse may limit the visible damage. I am fully aware that the physical appearance of a component does not always reflect its functionality, some failures can be spectacularly obvious and need no checking.

If the zener diode is intact then I would assume that downstream components would stand a fair chance of survival and there might be some hope of resurrecting the board.

Just musing.

Martin W

[Les Jones 1Participant @lesjones1]

Hi Martin (W),
I think you are probably correct that the zener Z1 will have provided protection to the rest of the circuit. I had looked at the wrong "K" terminals on the circuit. (I had looked at K1 and K2) and was thinking that there was no simple path for the fault current to get to the negative rail. The fact that it was K3 and K4 means that the zenner would have probably shunted the fault current to the negative rail and probably going short circuit in the process. Providing the fuse went open circuit before the zener was blown open circuit there hopefully will not be too much damage. I have been in touch with Martin K via email and he has confirmed that there continuity between the mains plug and the power input pins on the board. He only used a buzzer type tester as he does not have a multimeter. So the power light not lighting remains a mystery.

Les.

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