Solenoid and torch live. (euro torch)

[MartZ0r]

Hi guys, new to the forum here! i will be reading quite a bit on here and have been for a while.

I have a Romarc 160 amp welder i got off ebay with a wire feed problem, i solved the wirefeed issue (someone decided to cake the rollers in grease) but have noticed the torch stays live and gas stays on reguardless to the euro torch being plugged in.

So obviously a relay issue somewhere. They are removable and you can take them apart to inspect them. they have a clear cover.

it has a seperate relay for the wire motor, that works on the torch trigger fine.

there is another relay that activates when the power is turned on because i can see it move. i removed it and inspected the contacts. they were Ok.

i think the issue lies with the big power relay that goes to the Solenoid and the main tranformer unit. there is a clip on the side of it that has broken off so the switch is holding on one side. When i turn the welder on by the switch, this big relay instantly clicks on.

Here is a picture of the part i am talking about. The centre of this relay pops in when the powerswitch is turned on.

Hopefully someone can throw some advice my way, i am not too bad witch electrics, i have a clue but not a pro.

 

[Wedg1e]

That's the main contactor, it certainly shouldn't pull-in until you press the trigger.
I have a Romarc 200, the contactor is actuated from a relay on the control board (PCB terminals 8&9 is how I have it labelled)... might be worth tracing the wiring back from the contactor coil to the PCB and disconnecting it there; if the contactor stops pulling-in then it's definitely something on the PCB making it do so!

Ideally of course the missing clip could do with being replaced (or the whole contactor renewed) but it's hard to see how that would be the cause of the contactor actuating when it shouldn't be.

You could post a pic of the control board and I can tell you if it's the same as mine (for which I have the circuit diagram)... there's a 4000-series logic IC on there that was kaput on mine so it did some strange things when I got it.

 

[MartZ0r]

i have just eliminated the part that i thought it was by removing it, isolating the wires and powering it on. the gas solenoid still automatically turns on.


it's being turned on by this relay in the picture. i have opened the relay up and it looks fine, contacts are not stuck and it switchs when i turn it on. but as far as i can tell, it should not. so going to trace back the wiring further more to see what activates this one.

 

[MartZ0r]

the problem seems to be with the spot timer potensionmeter. Going to take a look at it.

 

[MartZ0r]

That's the main contactor, it certainly shouldn't pull-in until you press the trigger.
I have a Romarc 200, the contactor is actuated from a relay on the control board (PCB terminals 8&9 is how I have it labelled)... might be worth tracing the wiring back from the contactor coil to the PCB and disconnecting it there; if the contactor stops pulling-in then it's definitely something on the PCB making it do so!

Ideally of course the missing clip could do with being replaced (or the whole contactor renewed) but it's hard to see how that would be the cause of the contactor actuating when it shouldn't be.

You could post a pic of the control board and I can tell you if it's the same as mine (for which I have the circuit diagram)... there's a 4000-series logic IC on there that was kaput on mine so it did some strange things when I got it.

sorry i completly missed your post!

i will get a picture for you. but i have definitly found the issue. it's infact the "Weld Selector" Knob. it's very intermitent. if i apply a light bit of pressure to the knob, it works 100% but if i let it go, it wont work, and on the offchance it will for a bit then stop. but if i hold the knob it works 100% untill i let go.

looks like i need another one. Are they good Welders these Romarc's? they are packed with good stuff it seems.

EDIT (Pictures Added) ignore the masking tape, i numbered the wires because i removed the board. i have highlighted the problem part. i took the switch apart and cleaned it, my wire feeder works every time now but the gas solenoid and torch is still live and now i cant make it work by pressing on the rotary switch.

The switch needs replacing i think. i will try and source one and solder it in.

 

[Wedg1e]

Good news, that's the same control PCB

I'll try to scan the drawings, they're just freehand but you should get the drift.
The weld selector switch works in combination with one of the logic gate ICs to either switch in or out the timer circuits depending on whether it's normal, spot or stitch mode. I can't be certain but it looks like the IC numbers have been sanded off yours; mine had been as well but there are a couple of dodges to get round that.

On the 200 the gas solenoid is wired across the coil of the main contactor so that they're energised together. As you say it's the chassis-mounted relay (RLY1 on my dwg) that switches them, but that's triggered by a transistor on the PCB which in turn is triggered by a logic gate in one of the ICs. If the IC goes phut the transistor stays on... and so do the solenoid & contactor. A separate gate in the same IC triggers the wire feed motor circuit, so either gate going kaput is going to knock out some part of the welder (as had happened to mine).
I'm off to Peterboghorror for a few days early doors tomorrow so will scan and post the dwgs here, if the quality's not good enough I can email them on my return.

Romarcs appear to have been built by Technical Arc Services in York (same place that PortaMIGs come from, as well as the current crop of Oxfords!) using generally beefy components. Basic, simple circuitry but well-specified and should outlast most things from Italy or China

 

[Wedg1e]

OK, here goes... right-click on each drawing, select 'Save Picture As' and print to your heart's delight

 

[MartZ0r]

Thanks a million Wedg1e!

i am going to take another look tonight. i had the welder working fine every now and then, untill i messed with that Weld selector knob. now it's staying on again but when i did have it workings i noticed sometimes there was delay on the contactor, then sometimes there wasnt. my wire feed motor works fine though. i am going to take a look at the drawings.

Good news that its a similar/same setup for most parts.


Just a quicky though, do you know if the rotary switch (3 position 4 pole weld select knob) is make before break or vise versa, looking at the diagram id say it's a break before make.

Thanks again, will let you guys know how i get on.

 

[MartZ0r]

right after looking over the drawings, i think there "may" be some differences from the drawings compared to my board.

the 2 IC's on my board have quite a few legs soldered to them, more than what is shown on the PCB Diagram.

because both IC's have the numbers scratched off, i cant really de-solder and lift them to replace them.

leaves me one other option, i could make the Relay that is on the PCB (Relay 2) Directly activate Relay 1 at the same time.

 

[Robotstar5]

the 2 IC's on my board have quite a few legs soldered to them, more than what is shown on the PCB Diagram.

But do the "apparently" extra connections go anywhere? in some applications not all of the IC is used but spare legs are sometimes tied down to ground.

The IC's are probably the same as Wedgie posted so it might be worth desoldering and fitting dil sockets then you can "plug & play"

 

[MartZ0r]

thanks guys for the help!

they are ever so slightly different boards. i compared a picture from mine against a 200 board, its the same pcb and pretty much same components apart from a few things. i do think though they may be the same chips.

ordered me a new rotary switch for the weld selector. pretty sure is knackered so i will go from there.

i have a hot air/ solder rework station so i dont have any problems lifting the chips. as you say i could solder in a bed for the IC's so i can swap them.

i managed to do some welding with it earlier, to be fair, it is nice to weld with, quite a smooth wirefeed. I i dont have any steel thicker than 3mm to hand, but what should i expect out of this welder without a V-Root? like a butt joint? i dont really know the duty cycle of these old things.

 

[MartZ0r]

my rotary switch turned up today so i soldered that in today. i used some thin strand wire as i didnt have any kynar wire to hand so the colours didnt match. i took the wiring points for the little wires from the back of the board.

now my weld selector works fully, on all settings. so thats part of the problem fixed. the contactor is still staying live though. So it has to be that Logic chip.

i ordered some logic chip sockets and some replacment IC's y'day so they will probably be here tomorrow.

pic of the new rotary switch

 

[Wedg1e]

thanks guys for the help!

they are ever so slightly different boards. i compared a picture from mine against a 200 board, its the same pcb and pretty much same components apart from a few things. i do think though they may be the same chips.

ordered me a new rotary switch for the weld selector. pretty sure is knackered so i will go from there.

i have a hot air/ solder rework station so i dont have any problems lifting the chips. as you say i could solder in a bed for the IC's so i can swap them.

i managed to do some welding with it earlier, to be fair, it is nice to weld with, quite a smooth wirefeed. I i dont have any steel thicker than 3mm to hand, but what should i expect out of this welder without a V-Root? like a butt joint? i dont really know the duty cycle of these old things.

That photo on the right is my 200, as I bought it from another forum member. I think the obvious modifications were just to get round having to trace the existing circuit but I wanted it back to original so I stripped the extras off and rebuilt it.

Based on my two other MIGs (both built by the same place as the Romarc) I'd guesstimate 130-140A at 100% duty cycle. My Oxford 120s can do 80 (or 85)A at 100% and the Oxford 300, 225A at 100%. Averaging those two values suggests 141A. My Romarc has no data plate on it but it sounds plausible

If changing the ICs doesn't fix it, it could be one of the two transistors just adjacent to the relay, gone short-circuit (collector-emitter short as it's known). Effectively it becomes a wire link, taking the relay coil straight to ground and switching it on.

If you want to date it, big electrolytics and most transistors usually have a date code (like 42/89 for week 42 of 1989). Think mine's '84 or thereabouts...

Good effort so far, you could do my job!

 

[MartZ0r]

hey wedg1e, what job would that be then?

i dont suppose you know witch IC is witch? if not il find out by following the diagram anyways.

going on what you said about the sorted transistor, could i test that by doing a continuity check accross the legs?

 

[MartZ0r]

Here we go then. i have soldered both the new IC socket beds in place. i managed to remove one of the old ic's intact, the other i managed to pull a leg off. they were very weak and corroded.

Wedg1e, suppose you know which one is which, the one has ZZ4/L/I under the chip, the other has 6687 under it. not sure if any relevance. i am struggling to identify them by the diagrams.

i am going to check the transistors over and make sure they are operating correctly.

 

[MartZ0r]

seem's i am loosing the battle.

plugged the board back in with the new logic chips. they were in the correct way. plugged it in and same problem again. the relay triggered.

must be something else. i cant make out the code on the transistors. other than one, looks like BC107 or something like that.

 

[Wedg1e]

Hey up Mart, sorry for the delay, I was in Tallinn for a boozy/foody weekend

Yes, BC107 is a valid transistor type. Cost buttons if you can find someone who has them: Maplins maybe. If not there are literally thousands of other types that would do the job in that application. You could check for collector-emitter short with a multimeter on Ohms across the leads: if it's kaput you'll see the same resistance both ways round and probably less than about 50 Ohms - nearer to zero Ohms if it's totally fuackered!

Haven't got my glasses on so can't be sure but it looks as though you may have one of those IC sockets in the wrong way round! Only a small point but if you look you'll see there's a D-shaped dimple at one end that matches the dimple in the IC itself: the idea is that it shows which way round the IC should be fitted. Not picking fault as you're giving it a good stab but maybe years in the future when you come to change one of the chips you'll look at the socket and plug the IC in the wrong way

The IC nearest centre of the PCB is the 4093. The marks you mention are probably batch codes.

Anyway.... I'm a service techie in the non-destructive testing industry. So anything from handling radioactive materials to replacing blown transistors, building x-ray bays to calibrating radiation monitoring instruments... all in a day's work

 

[MartZ0r]

Thanks Wedg1e, i know how it is.. i had to crack some bottles of bud myself! im very greatfull for the help i have been given and im not in any rush. i love messing with stuff.

Haven't got my glasses on so can't be sure but it looks as though you may have one of those IC sockets in the wrong way round! Only a small point but if you look you'll see there's a D-shaped dimple at one end that matches the dimple in the IC itself:

glasses? don t think you need them haha because i installed the socket and i never even noticed. never installed sockets before but i have soldered resistors and IC's directly to the board.

because the kind of bloke i am i am going to turn it the right way around or it will annoy me haha.

i will get my meter on the transistors to see what i can find. if i find a blown one, how do i go about finding what one i need to get without being able to see the code stamped on it?

Anyway.... I'm a service techie in the non-destructive testing industry. So anything from handling radioactive materials to replacing blown transistors, building x-ray bays to calibrating radiation monitoring instruments... all in a day's work

blimey, that is some interesting work. i bet you get danger pay! i do automotive myself.

btw, nice big workshop and tool's

 

[Wedg1e]

i will get my meter on the transistors to see what i can find. if i find a blown one, how do i go about finding what one i need to get without being able to see the code stamped on it?

You need to get your TITS out!

Don't panic: Towers International Transistor Selector is (or used to be) the electronics techie's best friend after his multimeter. It's a massive cross-reference of virtually every transistor ever made, their operating parameters and equivalent types from other makers. Of course now these youngsters have the internanny to bale them out but I tell 'ee, we 'ad it 'ard. You'd get to the workshop before it got light, make a cuppa by the warmth of a soldering iron plugged into a light fitting, put your back out lifting a telly/radiogram/microwave oven/fat bird's vibrator onto the bench, spend three hours getting the covers off, blow out a thousand dead spiders (mostly straight into your brew, which by now was cold anyway), give yourself five high-voltage shocks from the various charged bits, cut yourself a few times on jagged edges of stamped steel chassis, rummage through ten thousand manuals to find a circuit diagram (which inevitably was for the Mk. 2 version when you had a Mk. 1 in front of you), take a few thousand volts more up your arm (or better still, across your chest) just for a laugh, trace the entire board to find a thruppeny transistor blown, read TITS from cover to cover to find an equivalent, phone every supplier in the whole world to discover there wasn't one in stock anywhere then pinch one that was 'close enough' from the secretary's Alba transistor radio while she was off-loading last night's chicken korma.
Then you'd solder it in the wrong way round, apply power, hear the pop, see the smoke and quietly put the whole pile of cack back on the 'Goods In' shelf for someone else to sort out on Monday morning

You already mentioned a BC107; that's exactly the sort of tranny I'd expect to see in that application - small signal NPN, 40 to 60v and a couple of hundred milliamps collector current is all that's required.

Edit - here you go: Maplins...

http://www.maplin.co.uk/low-power-lf-npn-transistors-to92-case-32952

2N3904 would do it, the 'pinout' for the BC107 is e-b-c viewed from underneath with the emitter nearest the tab (you'll see what I mean). The 2N3904 is e-b-c from left to right when looking at the flat face with the type number on it; another transistor might have the leads in a different order (eg. e-c-b) but you could turn it or bend the leads to make them fit.

blimey, that is some interesting work. i bet you get danger pay! i do automotive myself.

Er.... in principle it is. In practice there are too many chiefs, not enough Indians, too many projects, insufficient time, materials, tools or overtime pay.

Danger pay? My ar53. Stick with cars, I sometimes wish I had

 

[MartZ0r]

Lol, what an amusing post. the girlfriend looked at me like i was crazy while i sniggered at the monitor. you do know your stuff'

i will pull the board out and prod the trannys with my testing equipment. the board is back in the welder as i needed to do a few jobs on a disposable crappy cylinder. im collecting my gas friday so i will probably sort it tomorrow. i recon i will find something on the meter.

i never bothered checking them before, probably should have just to eliminate them before i lifted the IC's.

Thanks for the reference, il let you know how i get on with it tomorrow, thanks again bud!