It looks as if the original had been replaced if it's not giving the range, before dashing out and sourcing a new one, measure the current flow through the motor at full speed and also at minimum speed. That will give a two currents and then the new ww pot size can be chosen a bit better.
- Thread starter a111r
- Start date
Ahh, the problem with digital meters and their ranges 
0.3A means anything from 250ma to 349ma. The range of the pot is probably too low to make a 100ma swing in the current.
It matters not, If we assume 300ma is the max at 110V we would want for say a swing from about 10% through to 100% or 35ma to 350ma (It's debatable if the motor will even start at 35ma but you never know). 110 / 0.3 is 366 ohms (this is AC so not strictly the same as DC resistance but we're ball park figures here). To get 35ma we'd need 110 / .035 = a total of 3142 ohms. Take off the 366 and we're left with 2776 ohms - nearest E12 is 2.7K.
I'd doubt you'll find a 2.7K wirewound - more like 2.5K but even that seems a bit too high.
Before rushing out and spending on a 2K pot, do you have any wirewound resistors to hand, I'd try sticking a couple of 1K 5W wirewound resistors wired in series in place of the pot and see if the motor will start. It should do if my maths is right but whether it will with a bit of wire to push through is a different matter.
Slaying a chicken and seeing how the entrails lie, 500 ohm on a loaded motor feels better than 2K
0.3A means anything from 250ma to 349ma. The range of the pot is probably too low to make a 100ma swing in the current.
It matters not, If we assume 300ma is the max at 110V we would want for say a swing from about 10% through to 100% or 35ma to 350ma (It's debatable if the motor will even start at 35ma but you never know). 110 / 0.3 is 366 ohms (this is AC so not strictly the same as DC resistance but we're ball park figures here). To get 35ma we'd need 110 / .035 = a total of 3142 ohms. Take off the 366 and we're left with 2776 ohms - nearest E12 is 2.7K.
I'd doubt you'll find a 2.7K wirewound - more like 2.5K but even that seems a bit too high.
Before rushing out and spending on a 2K pot, do you have any wirewound resistors to hand, I'd try sticking a couple of 1K 5W wirewound resistors wired in series in place of the pot and see if the motor will start. It should do if my maths is right but whether it will with a bit of wire to push through is a different matter.
Slaying a chicken and seeing how the entrails lie, 500 ohm on a loaded motor feels better than 2K
That's what the entrails predicted
Have you got a 500 or 470 ohm power resistor ?
Without circuit diagrams and details, we're down to component substitution to find something that will just allow the motor to spin.
On the older post linked earlier, it did look as if there was already a 71 ohm 11W power resistor in series with the pot so we could well be looking for something lower than 500 ohm, possibly 100 ohm would be a good so anything in your collection in that range would be a good start.
Have you got a 500 or 470 ohm power resistor ?
Without circuit diagrams and details, we're down to component substitution to find something that will just allow the motor to spin.
On the older post linked earlier, it did look as if there was already a 71 ohm 11W power resistor in series with the pot so we could well be looking for something lower than 500 ohm, possibly 100 ohm would be a good so anything in your collection in that range would be a good start.
This might now be an "unfinished project"...
A minty original AW-2 has just appeared on Ebay:
A minty original AW-2 has just appeared on Ebay:
Vintage Norman butter.NBC Autoweld 2 mig welder.240 volt | eBay
Find many great new & used options and get the best deals for Vintage Norman butter.NBC Autoweld 2 mig welder.240 volt at the best online prices at eBay! Free delivery for many products!
www.ebay.co.uk
The chassis was made into a welding cart last month.
Last post on this thread, then.
I'll be hoarding the AW2 spares for years I expect, so if anyone needs a circuit board, transformer, Parvalux motor etc, PM me and I'll list the parts here for sale.
Show us your welding cart/trolley...
Have a look at mine earlier in the thread .................................................. There are 380 posts in this thread to search through, so could you specify the number of the post you are referring to please ?
www.mig-welding.co.uk
Last post on this thread, then.
I'll be hoarding the AW2 spares for years I expect, so if anyone needs a circuit board, transformer, Parvalux motor etc, PM me and I'll list the parts here for sale.
fridgefreezer
Member
- Messages
- 31
Just came across this while (still) searching for a manual for mine - @a111r if you'd be able to send me a copy that would be hugely appreciated, I could be interested in any spares you've got left too if the price is right.
Mine just popped the contactor coil (110v AC rated for reference) after all these years so I've been doing a mild restoration.
For my sins I drew the original hand drawn & probably wrong circuit diagram that's in the manuals section here - in the intervening time I've gathered a few more snippets of info from here & elsewhere - I've attached the most useful bits for the benefit of anyone else - the Parvalux motor order is my own as currently fitted to my welder and working great.
Here's my original thread trying to diagnose mine, including awful circuit diagram.
The other diagrams come from a thread by FarmerPalmer: https://www.mig-welding.co.uk/forum/threads/old-nbc-welder-new-problem.70704/ but he has gone quiet and never responded to messages - I would gladly scan in & PDF any paper manuals for everyone to use.
The socketed relay is compatible with an Omron MKS2PI AC24 or similar.
The socketed diodes can be replaced with standard rectifiers at least 200v/3A rating (the motor is 110v/2.8A), Vishay GBPC608-E4/51 is overkill but £2 each from RS, anything with ~10mm lead spacing will sort-of plug in.
The socketed timer module I've not really worked out yet but I'm fairly sure it can be ignored in normal operation and/or bridged out.
The other relays I'm working on identifying suitable modern replacements.
One day I'll actually convert the proper circuit diagram into a new main control board PCB and bring the unit into the new milennium
Mine just popped the contactor coil (110v AC rated for reference) after all these years so I've been doing a mild restoration.
For my sins I drew the original hand drawn & probably wrong circuit diagram that's in the manuals section here - in the intervening time I've gathered a few more snippets of info from here & elsewhere - I've attached the most useful bits for the benefit of anyone else - the Parvalux motor order is my own as currently fitted to my welder and working great.
Here's my original thread trying to diagnose mine, including awful circuit diagram.
The other diagrams come from a thread by FarmerPalmer: https://www.mig-welding.co.uk/forum/threads/old-nbc-welder-new-problem.70704/ but he has gone quiet and never responded to messages - I would gladly scan in & PDF any paper manuals for everyone to use.
The socketed relay is compatible with an Omron MKS2PI AC24 or similar.
The socketed diodes can be replaced with standard rectifiers at least 200v/3A rating (the motor is 110v/2.8A), Vishay GBPC608-E4/51 is overkill but £2 each from RS, anything with ~10mm lead spacing will sort-of plug in.
The socketed timer module I've not really worked out yet but I'm fairly sure it can be ignored in normal operation and/or bridged out.
The other relays I'm working on identifying suitable modern replacements.
One day I'll actually convert the proper circuit diagram into a new main control board PCB and bring the unit into the new milennium
Erie Fred
Member
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- 5,079
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- Erie, Pa USofA
fridgefreezer
Member
- Messages
- 31
Progress;
RL1 and RL3 can be made into standard socketed type relays using Omron 8-pin (PL08) socket (RS# 827-8416) which goes into a 30mm hole.
RL1 and RL2 can be replaced with Omron MKS2PI AC24 (RS# 536-893 about £10 each)
RL3 can be replaced with Omron MKS2PI 110VDC (RS# 215-7291 about £10 each)
The timer unit socket is an Omron 11-pin timeswitch socket, RS# 172-1219 works.
I replaced the contactor with an IMO MC40-S-00 with 110VAC coil, that appears to be working.
With this and the info collected above I will try to update the circuit diagram to make it clearer / hopefully correct.
Last job is to replace the capacitor bank, those are 4700uF 63v rated (Epcos B41252A8478M000 / RS# 771-4721 look a good bet)but I'm not 100% clear on the resistor values / ratings or the value of the fuse wire used to wire them up just yet.
EDIT: Found them - they're still made by Welwyn in their W20 series;
The small resistors are 220 Ohms (220R) W22 Vitreous enamelled wirewound resistor, 7W, 200V, 1%, 75ppm/°C
The big ones are 1.8 Ohms (1R8) W24 Vitreous enamelled wirewound resistor 14W, 750V, 1%, 75ppm/°C
RS and Farnell stock the range but not these specific values.
RL1 and RL3 can be made into standard socketed type relays using Omron 8-pin (PL08) socket (RS# 827-8416) which goes into a 30mm hole.
RL1 and RL2 can be replaced with Omron MKS2PI AC24 (RS# 536-893 about £10 each)
RL3 can be replaced with Omron MKS2PI 110VDC (RS# 215-7291 about £10 each)
The timer unit socket is an Omron 11-pin timeswitch socket, RS# 172-1219 works.
I replaced the contactor with an IMO MC40-S-00 with 110VAC coil, that appears to be working.
With this and the info collected above I will try to update the circuit diagram to make it clearer / hopefully correct.
Last job is to replace the capacitor bank, those are 4700uF 63v rated (Epcos B41252A8478M000 / RS# 771-4721 look a good bet)
EDIT: Found them - they're still made by Welwyn in their W20 series;
The small resistors are 220 Ohms (220R) W22 Vitreous enamelled wirewound resistor, 7W, 200V, 1%, 75ppm/°C
The big ones are 1.8 Ohms (1R8) W24 Vitreous enamelled wirewound resistor 14W, 750V, 1%, 75ppm/°C
RS and Farnell stock the range but not these specific values.
Last edited:
fridgefreezer
Member
- Messages
- 31
Well, update is that it all went back together - new relays, caps, resistors, replaced fixed relays with socketed ones, replaced diodes with bridge rectifiers - and it works lovely.
Pretty much all parts came straight from RS as fairly standard off-the-shelf stuff, current parts shortages notwithstanding.
Pretty much all parts came straight from RS as fairly standard off-the-shelf stuff, current parts shortages notwithstanding.
Farside
Badly Welded Man
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- 5,829
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- Ireland
At least it died with its boots on.
