clarke 100e wire feed problem

[sapwood]

Hi... Finaly got somewhere with this pcb..
Identified a resistor 10ohm 5%, that wasnt registering anything at all. The rest were giving me something, I took the problem resistor out and tested it off the board, still nothing. So ive ordered a couple and will fit one when they arrive.
Hoping this should be a 10p fix? Hey Ho!

 

[keith19]

Lets hope so! Let us know how you get on, always interesting: may help another of us down the line...

 

[darrylp]

okay, that resistor looks to be feeding to one of the junctions on the transistor ( the three legged semi circle thingy you called it )

get the letters numbers off that as well. as I'm betting that might be blown as well.

in those two black circles are two zener doides the orange -ish coloured ones second in from the right, their body is actually glass. they will need testing the same as the blue circled diode, but depending on your multimeter might show as okay both directions of swpping the leads around.

post on here the transistor part no. i expect its a common switching transistor, and if the 10 ohms has burnt out , then a lot of current was flowing before its destroyed the resistor and i expect the transistor will be damaged as well. its likely failed before the resistor, which caused the resistor to go.

 

[sapwood]

okay, that resistor looks to be feeding to one of the junctions on the transistor ( the three legged semi circle thingy you called it )

get the letters numbers off that as well. as I'm betting that might be blown as well.

in those two black circles are two zener doides the orange -ish coloured ones second in from the right, their body is actually glass. they will need testing the same as the blue circled diode, but depending on your multimeter might show as okay both directions of swpping the leads around.

post on here the transistor part no. i expect its a common switching transistor, and if the 10 ohms has burnt out , then a lot of current was flowing before its destroyed the resistor and i expect the transistor will be damaged as well. its likely failed before the resistor, which caused the resistor to go.

The resistor 10k turned out to be fine, it was my multimeter not giving a readin for a resistor so small. Bummer.
Ive been told now its probably the transformer, but need to know where to get one and the type?
Im getting an arc at torch so ive ben told the relay is fine, ive checked all resistors and their fine, so this just leaves the diodes and transformer. Oh and also those glass orange things you mentioned.
Would you advise on how I check these orange things.?
What would you do next.?
If I order a transformer and its not that, then im verymuch creaping toward a situation where simply paying the £40 and replacing the whole board would have been better. Considering the time ive spent on this now and lack of results.

 

[keith19]

Some help on testing zener diodes here:

http://www.tpub.com/celec/47.htm

But this site gives a less tech and easier to understand explanation, despite the sometimes fractured English:

http://www.protech2u.com/testing-zener-diode.html

As already been mentioned, you really need to remove components from the board for testing, to do it properly. But if that resistor was okay, and nothing else on that pcb is shot, it looks like the trouble may be elsewhere.

 

[sapwood]

Got round to working on the welder a little more recently. To my horror the 10k resistor I figured was faulty turned out to be my multimeter failing to give a reading for a resistor so small. Any other DECENT multimeter gives a reading. Bummer!
Some advice AShley gave me was that given the fact ive got an arc at torch and trigger works, its probably the transformer. All resistors are fine, this leaves just transformer or diodes.
WHAT WOULD ANY OF YOU GUYS DO NOW?
If I buy a transformer and it isnt that, then im begining to creep upto the fact that buying a complete £40 new board from Clarke is begining to look like the best alternative, given the time and ever increasing money im spending on this.
Does anyone know the transformer needed for this 105en turbo model.

 

[keith19]

When you say transformer, you mean the wire feed motor transformer on the pcb board we've been looking at?

You can check that out by finding the input terminals and measuring the resistance value through that side of the transformer.
Then measure the value across the output terminals for the other side of the transformer.

The values should be pretty close to what Scott posted much earlier in this thread for Mini Mad's m/c. http://www.mig-welding.co.uk/forum/showthread.php?t=30536&page=2

If one side gives no reading (always double-check), the windings in that side have gone, so a new transformer is needed.

There is only one diode left on that pcb if you've checked the zeners, and that is a simple current one way, no current the other way, test.
No current both ways means the diode has gone open, and current both ways means the diode has failed shorted or closed.

I'd do these tests before buying a new transformer; make sure the old one is dead first...

 

[sapwood]

When you say transformer, you mean the wire feed motor transformer on the pcb board we've been looking at?

You can check that out by finding the input terminals and measuring the resistance value through that side of the transformer.
Then measure the value across the output terminals for the other side of the transformer.

The values should be pretty close to what Scott posted much earlier in this thread for Mini Mad's m/c. http://www.mig-welding.co.uk/forum/showthread.php?t=30536&page=2

If one side gives no reading (always double-check), the windings in that side have gone, so a new transformer is needed.

There is only one diode left on that pcb if you've checked the zeners, and that is a simple current one way, no current the other way, test.
No current both ways means the diode has gone open, and current both ways means the diode has failed shorted or closed.

I'd do these tests before buying a new transformer; make sure the old one is dead first...

You couldnt explain to me these few steps please Kieth.. I understand the tests you say, but not 100% sure how their done. Am I testing this whilst its on the welder and switched on for anything over the transformer?

 

[shenion]

You measure the resistance of the transformer while powered off.

Post a picture of the back side of the board and we can show where to measure.

 

[sapwood]

Kieth I have measured the secondary and primary as in the picture you pointed to me. On my multimeter set at lowest point of 20ohms the primary ( two pins furthest away measured 19.1 to 18.4 and was drifting between these two numbers. The secondary ( two pins closest) was only measuring 0.1 and sometimes dropping from this to complete zero, seemed intermittent, similar reading I was getting when measuring the 10k resistor when I thought that was shot and it turned out it wasnt, it was my meter.
One last thing then, how do I check the diodes for currnt one way only?

 

[sapwood]

Heres the pics of the board and the pins I tested on multimeter set to 20ohms.

 

[sapwood]

this transformer only seems to have two pins on either side of it going into the board, ive marked them in this pic.
The red markings are where their is a series of solder points where you would think pins from the transformer as its directly above thes, but NOTHING through the board, just blank solder markings. The actual places where pins come through are marked in white.

 

[sapwood]

heres what im getting when I measure these pins. See Pic

 

[keith19]

Would suggest you turn up the meter to the next setting range on the secondary windings, and see what we get. If they've burnt/broken but still touching you can get a residual reading.

 

[sapwood]

whichever reading I set resistance at im getting the same reading Kieth.
arround 0.04 on the top two pins (red) and nothing on the bottom two (Yellow) and thats measuring on the next highest resistance setting on my meter of 2000ohms

 

[shenion]

They may have several transformers and pick the one they can get. The unused pins are for other versions.

Sounds like the transformer is fine.

Could be the diode or a bad connection outside the board.

 

[sapwood]

so if the resistors are all fine, the transformer is fine this leaves me with the following ive marked in this picture that could be faulty?
Wouldnt be something as simple as the pot would it, as when testing that with the meter it was registering resistance fine from 1-7 then when it gets to 7 it suddenly drops, despite raising the pot to 10 it drops off completely, is this normal?
With what is left now that ive marked in this picture, what should I do now you think?

 

[shenion]

Could be the transistors or the diode.

The pot may not measure well when in the circuit. It is 1000 ohms. Shouls measure 1000 on the outer terminals and 0-1000 on the center to one of the outer terminals.

I assume the relay clicks as I think you said you get and arc but no wire feed. That says the diode is probably fine.

 

[sapwood]

What do I do now Shanion mate? Im lost?
Ever tempted to simply replace the whole board and pay the £40 to Clarke for this.

 

[shenion]

Unless you know someone who can measure things whil it is running and trace the signals, replacing the board will be simpler.

You could try replacing the two transistors.