NBC Autoweld2 control transformer burned out, can anyone help?

[fridgefreezer]

I have an NBC (Butters) AutoWeld2 which is God knows how old (or it may be older than God, I'm not sure).

Anyway, the control transformer (wot makes things click) has burned out - the main transformers are still fine. I reckon it should be easy enough to pop a new universal transformer in there to bring it back to life but I have no idea what voltage I would need.

If anyone can help (a service manual would be perfect, I'd happily pay for someone to copy one for me) it would be much appreciated.

Failing that, a poke about in a working unit with a multimeter or just some general advice on faulting welders would be groovy - anything to save me having to reverse-engineer the circuit and trace all the dusty old wiring through the unit really!

 

[DIY Welding]

You need to find what input voltage (should be 240 ) and what are the secoundry output settings you cant get the exact one but there are replacements on the market thanks Mike

 

[fridgefreezer]

Well I'm figuring it will be a common voltage like 110 or 24v otherwise they'd have to use custom solenoids, relays, wire feed motor...

 

[DIY Welding]

The old NBCs where 110V would need to the exact voltages not somthing you can guess

 

[shenion]

You could look at the contactor, it may say "24V coil" that might indicate the transformer voltage.

 

[fridgefreezer]

Well, after a day spent reverse-engineering the thing I think I've gotten to the bottom of it...

It wasn't the transformer that let the smoke out, it was the wire feed motor just above it.

It's a DC shunt-wound motor so it seems what they do is leave the field windings connected to 110v DC all the time and then energise the armature to make it spin. Unfortunately the field coils didn't like this after a long period of being energised with no motor action to cool them down and have gone toasty.

To find this I also had to repair one of the rectifiers (the one that supplies the motor) as two of the diodes in it had gone s/c, I don't know which caused which but with the rectifier back I could power it up without the panel fuse blowing, at which point the motor made a crackly noise and let some more smoke out

So, not an ideal result but at least it's not the transformer, a motor can be replaced or possibly even re-wound (if it lasts another 30 years I'll be happy!), Monday's job will be a call to Butters or Parvalux who made the motor in 1972 and are amazingly still around and boasting about their reliability

New rectifier with shiny heatsink:

Not good :

 

[fridgefreezer]

Well Parvalux are shipping me a brand new motor, from the technical drawing of the old unit so it should bolt in. A bit pricey at £125 but if you average it out over the 35 years the old one lasted it's not bad value and cheaper than buying a new welder.

BTW if anyone needs the circuit diagram for an NBC Autoweld2 I have it scribbled on a bit of paper now

One thing that did come up in discussion with Parvalux was the idea of fitting a current limiter to the motor to prevent the coils getting hot when left on for a long time. I know such devices exist (thyristors?) does anyone have any thoughts on this?

 

[classic2cv]

Hi there if you could do me a copy of your wiring diagram for my Butters Autoweld just incase i have to any work on it

this is what my one looks like

i've seen some photos of an other on ebay and that one has metal sides

(the plastic sides on mine don't make it any lighter)

hope you get yours working again soon, it's a very good machine to have

 

[malcolm]

It's amazing you can still buy parts for a 35 year old welder. Well done to Parvalux for making the effort in supplying the parts.

If there's a scanned in image of the wiring diagram I could stick it up on the site somewhere - might be handy for others in the future.

classic2cv - hope you've given your welder a wash since the photo was taken

 

[classic2cv]

It's amazing you can still buy parts for a 35 year old welder. Well done to Parvalux for making the effort in supplying the parts.

If there's a scanned in image of the wiring diagram I could stick it up on the site somewhere - might be handy for others in the future.

classic2cv - hope you've given your welder a wash since the photo was taken

Posting the diagram would be a good idea as there might be a few more folks out there who might have one

my welder is in store at the moment

but when it comes out again

I’ll take the covers off (they just slide up & off) and give them a good scrubbing

 

[weldequip]

Posting the diagram would be a good idea as there might be a few more folks out there who might have one

There could be one or two in the British Museam
Sorry I can't help, well before my time in the job.
weldequip

 

[fridgefreezer]

Sorry for the shoddiness, they hid the crayons from me I may re-do it in a human-readable format at some point

"Left" and "Right" are as seen looking into the side of the unit, so "left" is towards the front panel and "right" is towards the back.

 

[fridgefreezer]

It's alive!

Parvalux took their time delivering the motor, a bit frustrating but then for a 35-year-old one-off job I guess I should be glad it arrived at all!

The motor was exactly to spec, as they said - however, the spec that Parvalux made them to is different to as NBC bolted them to the unit, I had some work to do:

- Enlarge & tap four holes in the top of the casting to M5
- Cross-drill the shaft to take a roll pin that holds the drive gear on, I used a 3mm drill bit as that's what was about. Had to source a 3mm roll pin too
- Chop the end of the shaft off once the drive gear was on, it is supplied about 1" too long.

Once that was all back together with the gearbox, it just remained to get the wires the right way round (there are no polarity markings) and it's back to full health.

Now to fit some neons, slam it to the deck and bolt some spinners on

 

[henvoy]

can it operate without the gas?