Found one off, imagedude, it had two wires piggybacked onto it. Once I pushed it back onto the terminal, things started to get better, but still no arc or current at the torch tip.
- Thread starter miggins
- Start date
Hi Radar. There is continuity between the wire protruding from the torch tip and the wire reel inside the casing. No continuity on the cable from the wire feed motor connection back to the transformer. Have to leave it for today, however, it's 3.5°C in the garage!
It seems that things have improved, now the only missing function is the arc. Was this change due to the loose push-on spade tag at the PCB? In post #13 imagedude said he had problems with the spade connectors.
Your photos show that, as you said, a Portamig mostly consists of an empty box. Surprisingly for a "pro" machine, the auxiliary power is a small plastic-encapsulated PCB-mounted transformer ( the brown box ), the "Contactor" may be only a medium-sized PCB-mounted relay ( the white box? ), and the main welding transformer has a centre-tapped secondary with just two diodes for the rectifier.
To diagnose the "no arc" issue:
- have you tried all settings of the power selector switches?
- check the AC secondary voltage between the two bolted connections to the heavy steel tags at the top of the rectifier. With a centre-tapped transformer, this will be double the expected welding voltage - about 30 to 50 volts AC
- check the DC output from the rectifier, between the bolt on the lower left corner of the cooling plate, where it joins to the inductor ( negative ), and the floating bolted connection to the black flexible cable ( positive ) - about 15 to 25v DC.
Both these AC and DC voltages should rise in steps as you switch up the output power ranges.
Finally, trace that heavy black flexible wire up to the brass block of the Euro socket. Measure the DC voltage from there ( + ) to the back of the Dinse socket for the work return cable, on the front panel ( - ).
Thanks Eddie.
I will take another look tomorrow when hopefully it's warmed up a bit.
Thanks for taking the time to suggest possible solutiins/ workarounds, much appreciated.
GrahamGKD
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When I bought my Portamig 13 or so years ago Steve at Weldequip tipped me off that you had to go to the 215 machine to get the 'chunky contactor' (as opposed to a PCB mounted afair). Incidentally, I hammered my 215 (now sold on) until a few weeks ago and never had a single problem with it :-).
Hi Eddie.
Very cold in the garage this morning so I didn't linger.
Voltage readings, with torch triggered:
AC potential across rectifier plate bolts 24.85V
DC potential across Eurotorch connection and floating black cable connection: 35.5V
Dc potential with meter connected to Eurotorch brass block connection at wire drive and ground return terminal 28.77V
tried striking an arc on a piece of scrap steel and got a few sparks, suggesting steel had a non-conductive coating on it. No joy trying on the earth clamp itself. Maybe I need to set up for a real weld and see what happens.
Will post again after a test weld.
Cheers Eddie.
Hi Eddie. I put the meter on the wire as it emerges from the torch tip and got 548mv, so clearly the power isn't getting through. Off to the repair shop it seems.
I'm confused by the voltage readings.
I would expect the normal range of DC welding voltage output to be from 15v ( at 20 Amps ) to 25v ( at 185 Amps ), varying smoothly as the power control switches are stepped up. This should be present across the MIG torch tip to the work return clamp, and may also be stated on the machine data plate.
With a centre-tapped transformer and a two-diode rectifier ( as opposed to a "straightforward" secondary and four diodes in a bridge rectifier ), the end-to-end voltage across the full secondary will be double the required output. For example, for 25v output, a centre-tapped transformer would be described as "25-0-25".
The power range switches are on the primary tappings. When set to the lowest range, expecting to weld at say 15v and 20 Amps, the output of the secondary across the two bolted connections to the heavy steel tags at the top of the rectifier should be about 30v AC. If the machine was on the lowest setting, your reading of 24.85v is about right. It implies the lowest welding output voltage is 12.4v, which is just possible.
Could you please repeat that test, and step from the lowest power switch setting up to the highest? I would expect that 24.85v AC to rise to about 50 volts.
When you measured 24.85v AC across the transformer, your second reading was 35.5v DC out of the rectifier. I would have expected 12 to 13 volts. This is between the bolt on the lower left corner of the rectifier cooling plate, where it joins to the inductor ( negative ), and the floating bolted connection to the black flexible cable ( positive ).
Both these AC and DC voltages should rise in steps as you switch up the output power ranges, please try this.
From the brass Eurotorch socket at the wire drive assembly to the ground return terminal ( the Dinse socket on the front panel ) you saw 28.77V. This implies that 6.73 volts was dropped across the inductor. If that's true, there is a very high resistance coil or a bad joint there.
Finally, the 0.548v on the MIG wire at the torch tip ( to the work return clamp ), when compared to 28.77v at the Euro brass block, implies that the torch plug is not making any contact at all.
I would expect the normal range of DC welding voltage output to be from 15v ( at 20 Amps ) to 25v ( at 185 Amps ), varying smoothly as the power control switches are stepped up. This should be present across the MIG torch tip to the work return clamp, and may also be stated on the machine data plate.
With a centre-tapped transformer and a two-diode rectifier ( as opposed to a "straightforward" secondary and four diodes in a bridge rectifier ), the end-to-end voltage across the full secondary will be double the required output. For example, for 25v output, a centre-tapped transformer would be described as "25-0-25".
The power range switches are on the primary tappings. When set to the lowest range, expecting to weld at say 15v and 20 Amps, the output of the secondary across the two bolted connections to the heavy steel tags at the top of the rectifier should be about 30v AC. If the machine was on the lowest setting, your reading of 24.85v is about right. It implies the lowest welding output voltage is 12.4v, which is just possible.
Could you please repeat that test, and step from the lowest power switch setting up to the highest? I would expect that 24.85v AC to rise to about 50 volts.
When you measured 24.85v AC across the transformer, your second reading was 35.5v DC out of the rectifier. I would have expected 12 to 13 volts. This is between the bolt on the lower left corner of the rectifier cooling plate, where it joins to the inductor ( negative ), and the floating bolted connection to the black flexible cable ( positive ).
Both these AC and DC voltages should rise in steps as you switch up the output power ranges, please try this.
From the brass Eurotorch socket at the wire drive assembly to the ground return terminal ( the Dinse socket on the front panel ) you saw 28.77V. This implies that 6.73 volts was dropped across the inductor. If that's true, there is a very high resistance coil or a bad joint there.
Finally, the 0.548v on the MIG wire at the torch tip ( to the work return clamp ), when compared to 28.77v at the Euro brass block, implies that the torch plug is not making any contact at all.
Hi Eddie.
Feeling slightly despondent after having no luck yesterday, I took the machine to Ian Baird Welding in Nirth Walsham, Norfolk and Ian Baird himself took the welder into the workshop for testing. Encountering the same wire tip resistance problem he unscrewed the torch and found there had been some arcing on the brass connections. He tried another torch hanging up in the workshop and it worked fine. So, I bought a new torch, Lorch, at a generous discount and half an hour's labour, job's done.
Got the machine home and set it up and it was off like a steam train. I even managed to complete a welding job I had been planning and it didn't look too bad once I'd cleaned it up with the angle grinder.
I just want to thank you for all the interest you have shown in my problem and for all your technical suggestions; invaluable. I like to think I'm a gifted amateur but most of the time I'm probably fumbling in the dark.
Thanks again, Eddie.
Feeling slightly despondent after having no luck yesterday, I took the machine to Ian Baird Welding in Nirth Walsham, Norfolk and Ian Baird himself took the welder into the workshop for testing. Encountering the same wire tip resistance problem he unscrewed the torch and found there had been some arcing on the brass connections. He tried another torch hanging up in the workshop and it worked fine. So, I bought a new torch, Lorch, at a generous discount and half an hour's labour, job's done.
Got the machine home and set it up and it was off like a steam train. I even managed to complete a welding job I had been planning and it didn't look too bad once I'd cleaned it up with the angle grinder.
I just want to thank you for all the interest you have shown in my problem and for all your technical suggestions; invaluable. I like to think I'm a gifted amateur but most of the time I'm probably fumbling in the dark.
Thanks again, Eddie.
I asked Technical Arc about retrofitting a smoothing capacitor bank to my welder, but they say it would not be feasible. They even sell smoothing capacitors on Ebay!
Yes, I see that - they have 15, 22, and 47, 000 uF capacitors for sale.
The capacitors go across the DC output from the rectifier, before the inductor. Adding capacitors will increase the rectified DC voltage by x 1.414. Since the Portamig has decent low-power settings, this should still be OK for usage on thin metal.
With the small plastic-encapsulated transformer on the PCB ( as opposed to a medium-sized transformer to provide auxiliary power ), it is apparent that the wirefeed motor on the Portamig is run from the output of the main welding transformer. Adding capacitors will store a charge, and may cause the motor and the MIG wire to run-on after the torch trigger is released.
In addition, there will be a slight arc at the wire tip at the start of the next welding operation. This can be eliminated by using a relay with normally-closed contacts to switch a bleed resistor across the capacitors.
So retrofitting capacitors is not a one-step job, but it can be done. I could lend you a couple of capacitors if you wanted to check out the effect of adding them.
The capacitors go across the DC output from the rectifier, before the inductor. Adding capacitors will increase the rectified DC voltage by x 1.414. Since the Portamig has decent low-power settings, this should still be OK for usage on thin metal.
With the small plastic-encapsulated transformer on the PCB ( as opposed to a medium-sized transformer to provide auxiliary power ), it is apparent that the wirefeed motor on the Portamig is run from the output of the main welding transformer. Adding capacitors will store a charge, and may cause the motor and the MIG wire to run-on after the torch trigger is released.
In addition, there will be a slight arc at the wire tip at the start of the next welding operation. This can be eliminated by using a relay with normally-closed contacts to switch a bleed resistor across the capacitors.
So retrofitting capacitors is not a one-step job, but it can be done. I could lend you a couple of capacitors if you wanted to check out the effect of adding them.
GrahamGKD
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There was a thread on the topic of retro-fitting capacitors to Portamigs on here some time ago (maybe several years ago now!) - the conclusion was the same.
Lockdown boredom finally had me bite the bullet and upgrade to a bigger Tec Arc machine with capacitors and a four roll wirefeed. I think the Portamig 215 cost me something like £550 around 13 years ago and it sold for £320 - I was chuffed with that. Haven't really had chance to put the new machine through its paces yet so I'm not able to say whether the capacitors make much difference.
arther dailey
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easy answer to that dont work on renaults
,ha ,I mean why would you . Only joking of course , put some .6 wire in and you will find a sweet spot on those thin tins , its a bit fussy but you can get it just so ,my old tec arc 185? was spot on with .6 on thin thin and thin rusty stuff, did a rear quarter begrudgingly on brothers renault. which I may add he didnt give me a penny for, he then sold it on for profit...family,urghh...
malcolm
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My 181 was perfect for 0.6mm. Went to the 215 and it's useable on 0.6mm just not so flowy. It might just be me out of practice.easy answer to that dont work on renaults
I'm selling most of the Renaults this year.
GrahamGKD
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Maybe later ones did - mine didn't. I opened it up not so long ago - no capacitors, in fact the main thing I noticed inside was dust! Great machine though - it served me very well. Most of the work I used it for was 1.5mm upwards.
