180 Lincoln/Snap on/ ESAB smashweld needs rectifier diodes

[Lincsnap180]

Hello, good evening any readers?
First post for me, hope not ‘Last Post’ for the old Lincoln (re-built many years ago from 2 machines).
First activity on registering the forum has been hunting for posts addressing the topic of rectifier diodes.
So far, i have found reference to stud mount diodes but both donor machines had press fit diodes in groups of 4 or 5.
I can change a fuse(!) and could re-build the rectifier by copying but have no significant knowledge of electrical technology and have not yet found required semiconductors despite enquiry to specialist supplier.
TR231 and TR231R has not produced any search results.
If there is anyone who can remember these machines (later 1980s), could you please let me know of a replacement component, if there is one?
Replacements are needed for all the RIFA RC units, too. Probably time to replace main capacitors?
If it would be better to re-build using stud mount diodes then please let me know but without a circuit drawing for the revision i could be in trouble. The subsidiary rectifier plate with 2 pairs of diodes is a complete puzzle for me.
I would very much appreciate advice on repairs, please.
Thanks. J

 

[eddie49]

Hello and welcome to the Forum !

According to this thread:

E

Thread 'Help on rectifier diodes'

Jul 4, 2006

Hi Everyone,

My first post as a new member, I have a Migatronic Automig 180MXE, it has a blown bridge rectifier unit, two of the 16 diode had gone s/c.
My problem is finding out what the diode are?, no marking except the anode, cathode marking, some of the diode have been replaced with motorola tr231r, but yet again I can;t cross reference them, they are all the press in stud type with a flying lead.
I have contacted Migatronic and I am waiting for a reply, I expect no information only that the will gladly sell me a replacement unit for x amount.
The machine is getting on abit but is...

• Eurotorch
• Replies: 12
• forum: Migatronic, Thermal Arc

the TR231R diodes are made by Motorola, and are rated at 50 Amps each.

Post #14 of this thread:

Thread 'ESAB (Snap-on) Smashweld 180 Stuttering'

Dec 30, 2020

Hi All

I'm taking a look at a mate's welder that was returned to him after lending it out. It needed a new torch and wire and given it was in a bit of a sorry state, initially he though the wire feed motor had packed up, but we think that's because he'd forgotten to put the front toggle switch on the 'bead welding' setting

Putting it to the test, we then found it to be what I can best describe as 'stuttering' when running a bead weld across some 2mm steel. It was sounding like the arc transformer was tripping in and out. Given 50% of the strands on the earth clamp cable were...

• Graham Francis
• Replies: 25
• forum: ESAB

lists the various makers and names applied to this ESAB welder.

Post #14 here:

J

Thread 'Snap-On MB135 with slow wire feed'

Nov 26, 2020

First off I am a novice welder and I must say that I am no electronics wiz, I probably know just enough to be dangerous. I was given a Snap-On MB135 that at first would not feed any wire and I found a burned trace on the PCB with the feed controller on it (from the Line in in to a relay). I repaired that with a piece of wire. Voila! the wire started to feed again. Problem is it was welding like crap except every now and again on some thin sheet metal. After much research, figuring, and head scratching I came to realize that the feed rate is very low (about 230 inches per minute MAX). The...

• Jon Andriotis
• Replies: 17
• forum: Cebora & Snap-on

discusses the strange "two extra diodes" circuit.
That arrangement of two diodes and two windings on the inductor is often used by Cebora, and also this Blue-Point MIG:

Blue point MIG 115 Operating Instructions Manual (Page 11 of 12) | ManualsLib

www.manualslib.com

I think the circuit diagram in Post #1 of this thread applies to your machine:

F

Thread 'arco lincoln minimig 180c Wire feed motor not running'

Jan 10, 2021

Hi Everyone

I have just been given a old
arco lincoln minimig 180c I believe it was also sold as Snap-on minimig 180c
and ESAB Smashweld It has a fault that I was hoping

I could get some help with troubleshooting

The welder was working fine until it was fitted with a extra long torch then the Wire feed stopped working so far the I have checked the motor running ok with 12v supply the PCB Fuse checked Ok changed the feed switching relay on the PCB the main power relay seems to be working fine switching over when the trigger is pressed along with the new relay on...

• Florent
• Replies: 4
• forum: Welders and Welding Machines

Rather than rebuilding the bridge rectifier with press-fit diodes, or replacing it with four large stud-mounted diodes, many Forum members have obtained replacements from Tec-Arc in York:
!70 Amps

Pardon our interruption...

230 Amps

230 AMP SINGLE PHASE MIG WELDER FULL WAVE BRIDGE RECTIFIER | eBay UK

230 AMP RECTIFIER FOR MIG WELDER. TEC ARC is a leading manufacturer and repair centre of arc welding machines. Other rectifiers available including 130A, 290A, 400A single phase and various three phase rectifiers.

www.ebay.co.uk

They might be able to add the two extra diodes, or you could use two stud diodes, or ignore that arrangement.

 

[Lincsnap180]

Hello Eddie, thank you for welcome and numerous references including your earlier post!
I have read several posts, hope ihave read all the posts quoted, and posts within posts, but maybe got lost in the maze! My memory is not as i would like.
Evidently, others have tackled this problem before I met it.
Think i saw Florent’s post (Jan. 2021) some time ago before joining the forum.
Is it viable to convert this machine to the type with Semikron Diodes with braided leads? Has anyone done it? Please let me know!….and how to do it!
I saw the video of a Sealey machine being re-fitted with Vishay diodes but it is a much simpler design so I cannot copy the process.
Since posting, i remembered (from roughly 20 years ago) that i have the circuit diagrammes salvaged from the original machines. The circuit diagramme in your post is the same as from my machines (Lincoln/Snapon bitsa with homemade Eurotorch conversion). Unfortunately, my level of ignorance is such that i do not understand much of the circuit, its components or the conventions of representation. I soon realised that the actual number of rectifier diodes is not shown on the diagramme (full circuit drawing would be needed).
TecArc say that their product, RECT 151 (out of stock at present) is not a direct replacement for the original rectifier assembly but they will rebuild a customer’s original for a reasonable price. It looks as if the depth (thickness) of some of the TecArc rectifiers cannot be accommodated within the Lincoln/Snapon/ESAB casing which is very narrow.
Thanks, best regards, j

 

[eddie49]

Due to the issue of the narrow available space, it may be best to repair/rebuild the existing rectifier.
How many of the press-fit diodes have failed? Are they short- or open-circuit? Are the two strange "additional" diodes still OK?

To use four stud-mount diodes would require obtaining some finned heatsinks, mounting them with insulated supports, and ensuring good airflow - maybe adding a fan.

An alternative that may be worth considering is a modern "diode module", e.g.:

Pardon our interruption...

Again, a heatsink would be needed:

Pardon our interruption...

These components are not commonly seen in welders, but this thread refers to one:

A

Thread 'Dan-Mig 140 Bridge'

Apr 10, 2021

I'm new to welding and welding equipment. I came across a Dan-Mig 140 that is free for me to use/learn on. The one catch is I need to fix it first. I'm pretty sure I found the problem, one of the diodes in the rectifier is shorted out. Problem is, I can not locate a replacement, and it doesn't look anything like the other bridges I've seen on this forum. Pictures below. Any help would be greatly appreciated.

• akrover
• Replies: 9
• forum: Migatronic, Thermal Arc

The RIFA ( or WIMA ) noise-filtering/spike absorbing capacitors are mentioned in Post #6 of this thread:

Thread 'Esab Power Compact 160'

Nov 5, 2022

Just figured id put this up here incase its useful to anyone going forwards, little wiring diagram on the panel of the esab i just bought and some pictures of its insides

Not sure what i'm doing with this yet, it was cheap enough that if i have to scrap/strip it its fine

Not tried welding with it yet but it all sort of functions as it should, voltage goes up and down as it should with the selector switch, spot and pause timers work, wire feed control works but seems somewhat erratic when fiddling the pot, and the poor old electrolux motor squeals, control pot is definately tired

Main...

• Monkeypeas
• Replies: 44
• forum: ESAB

• 

Regarding the main electrolytic capacitors across the DC welding output:
these large capacitors can be tested by trying to charge them, briefly connecting each one to a few volts DC ( e.g. a 9 volt PP3 battery, or a few 1.5v AA cells in series ), and then confirming that they can hold this voltage for a while. Replacements for these "computer-grade" capacitors can be expensive.

 

[Lincsnap180]

Thank you for amazing amount of help, Eddie49! Busy here with MOT challenges now but will return to welder repairs, soon. Need more time to study your links. The Esab rectifier plates are same pattern as i have here.
I have not tested any diodes.
Had advice, from Les at TecArc, that the diodes in the circuit ‘downstream’ (as i think it) of the reactance /choke generally do not fail. None of the forward diodes (in either of the rectifiers) shows signs of failure. All the obvious failures have been reverse diodes and localised in one portion of the rectifier assembly.
Suspect that to be significant.
Have replaced the failed diodes with same type from spare rectifier. 1 substitute started to overheat.
I will try to find out how to post photos then it should be possible to provide better info. in case you or other welders might kindly provide solutions to the puzzle (after MOT).
My multimeter is AVO ‘Heavy Duty’ (must be nearly antique) and i must buy a ‘good-enough’ grade, reliable digital multimeter with diode and capacitor test facilities. Cannot afford a Fluke.
Wonder whether a thermal imager of some sort would be useful for diagnostic purposes, if affordable.
Any multimeter recommendations would be welcome, please.
Then i will try testing. Think multimeter must be first move.
Thanks and All the best…

 

[eddie49]

A digital meter cannot test a diode on the Resistance ranges, but it can when set to Diode Test mode.
However, a traditional moving-coil meter such as an Avo will be fine to indicate whether a diode is OK. Using the "Ohms x1" resistance range, expect the needle to go about half-way across the scale to indicate forward conduction, and stay to the left at "Infinity" to show reverse blocking.
[ Note that when using an analogue meter to measure resistance, the black meter lead is a source of Positive voltage.]

A fancy digital meter may have a Capacitor test range, but actually may not go as high as the 10,000uF components typically found in the capacitor banks of MIG welders.
Again, simply checking resistance on a good old Avo can indicate that a capacitor is not shorted and can hold a charge. The meter needle will initially swing over to the right, indicating low resistance, and then fall back to infinitely high resistance after the cap has charged using the voltage from the meter. Observe correct polarity - the black meter lead is Positive.

 

[500e]

I have 2x HE4.04 and 2x HE4.03 diodes out of an old Miller that was working ok if anyone can find a use for them. Cost of post only

 

[Lincsnap180]

I have 2x HE4.04 and 2x HE4.03 diodes out of an old Miller that was working ok if anyone can find a use for them. Cost of post only

A digital meter cannot test a diode on the Resistance ranges, but it can when set to Diode Test mode.
However, a traditional moving-coil meter such as an Avo will be fine to indicate whether a diode is OK. Using the "Ohms x1" resistance range, expect the needle to go about half-way across the scale to indicate forward conduction, and stay to the left at "Infinity" to show reverse blocking.
[ Note that when using an analogue meter to measure resistance, the black meter lead is a source of Positive voltage.]

A fancy digital meter may have a Capacitor test range, but actually may not go as high as the 10,000uF components typically found in the capacitor banks of MIG welders.
Again, simply checking resistance on a good old Avo can indicate that a capacitor is not shorted and can hold a charge. The meter needle will initially swing over to the right, indicating low resistance, and then fall back to infinitely high resistance after the cap has charged using the voltage from the meter. Observe correct polarity - the black meter lead is Positive.

Thank you for replies. Wonder why the preceding messages have been added to mine. Is that normal?

I will get on testing diodes asap. Evidently the old AVO has advantages though i believe it is a fairly delicate instrument. It is powered by only a 1.5 or 1.2 volt cell whereas Model 8 had 1.5 cell and, i think, a battery. My Model 8 came from a scrap yard and now has 1 broken hairspring after toppling over.
I am wondering whether the old Edgecumb Peebles would do the job, on Ohms range starting at 0.1.
Hope to get the hang of the diode test procedure and keep in mind that electrons have negative charge.

It seems that press-fit diodes are virtually unobtainable now. It is proving awkward to obtain stud-mount alternatives, too. It appears that the most suitable stud mount components are Vishay items (various current and voltage ratings available) taking dimensions into account. The Vishay diodes with braid leads would be handy, if available, to replicate the original design in ESAB/Lincoln etc though the new diodes would need to be set on a larger pitch circle diameter.

No progress with RS. I suspect that many ebay sellers do not actually supply genuine Vishay diodes, only look-alike.

The links (above, Eddie supplied) mention (somewhere i think) that the RIFA units are for protection against voltage spikes. Could their failure have contributed to loss of old diodes? Does using high volts rating diodes (some rated at 1600 volts) imply resistance to spikes?
Almost everything to learn!

Thank you for all replies.

 

[eddie49]

Even if an Avo has a 15v or 22.5v battery, the basic "R x 1" Ohms range will be using the 1.5v cell, and for a simple Go / No-Go test of a diode, that will do the job. So either a "Heavy Duty" or a later Model 8 Avo would be fine.

An Edgecumbe Peebles "METROHM" ( never heard of it till now ) is a transistorised "Megger". It may use up to 500 volts, so I would not recommend using it to test diodes.

Press-fit diodes are still available as "alternator diodes".
This company offers them:

https://www.gdrectifiers.co.uk/product-category/semiconductors/discretes/diodes/press-fit-diodes

Stud diodes? Get this one and then look for 3 more ....!

Pardon our interruption...

Here are 6, with beefy heatsinks:

Pardon our interruption...

Here are 4 x IR (International Rectifier) 70U 20P:

Pardon our interruption...

Apparently 200v, 250 Amp, so OK for a MIG.

These Westcode SW02PHR300 are 200v and 380 Amps! A set of five for only 30 Quid:

Pardon our interruption...

As mentioned, to use stud diodes or a "Diode Module" you would have to provide proper heatsinks, insulation, interconnect wiring, and maybe a fan too.

Hard to say if failed RIFA/WIMA capacitors caused diode failure. The casing of the caps can crack or split, but they may still work.
Diodes with high peak inverse voltage ( PIV ) ratings should be more resistant to spikes, but with imported "clone" components those specifications may be false.

 

[Dragnet]

AVOs are great. I use one regularly, and have a couple. Diodes are diodes, so don't get hung up on makes and types (but from a reputable supplier; as you mention, fake components are not uncommon). As long as you have some that are suitably rated, they'll work, so the main thing is to ensure you make fitting as easy as possible. Put the AVO leads across the diode and you should get low resistance one way and infinite resistance the other way, which means it's working.

What braided lead diode are you looking at? I can see some stud-mount Semikron components. A picture of the ones in your machine would be handy. I've not come across press-fit packages before, and am having some trouble finding references for the package standards.

Apart from the go/no go detailed earlier by eddie49, where one checks for a short by measuring the resistance, capacitor tests on DMMs are mostly useless. Unless tests are done at working voltage to check for leakage, which requires a dedicated tester, there's no way of knowing a component that tests OK on the bench from a 9V multimeter battery will hold up at hundreds of volts in use. I've made my own with switchable voltage and leakage display, and also have a hand-cranked Megger for the rare times I need 1kV, as that will show leakage through a resistance measurement.

I'd leave alone any big electrolytics as they'll only have an effect on welding, so get it running first. However, if you have any of the gold-coloured RIFA paper capacitors (code PME) as in the photograph in an earlier post, they're replace on sight for me. It's not a case of if they'll fail, but when. In a transformer welder, I'd replace with MKP - metallised polypropylene - capacitors, such as these, assuming the ratings and lead spacings match. Use properly rated X and Y types if the circuit requires it (something of this age will have them marked X2 or Y2 on the encapsulation, so replace like with like.)

Here're before and after pictures of a PCB from an ESAB Tigaid 315 I've just done that job on. Every single PME RIFA was cracked and leaky, as well as a couple of the smaller electrolytics (red cylinders). The RIFAs I've left are fine. A similar encapsulation, but a metallised film type rather than the paper PMEs which are known to fail.

To attach pictures, simply click the 'attach files' button to the bottom left of the 'reply' text box, and choose which pictures to upload and in which order. The messages were added to yours because you clicked 'reply' on the post itself. You can adjust the amount quoted, or add multi-quotes, by playing with the 'quote' and 'reply' buttons. Alternatively, you can use the box below the latest post to write a reply to the thread without quoting a previous poster, as I'm doing when typing this.

 

[Lincsnap180]

I cannot thank you enough for all this help!
Will try loading photos when my brain is clearer, must arrange track drives for the old digger and the price addles my brain.
My websearching has not been anything like as effective as yours. I had become pretty well hooked on Vishay VS-85HF120 (& Reverse version) for rebuilding a spare rectifier assembly, converting to stud mount. They are approx. £8.60 (maybe plus vat) each for 10+ from Mouser but no stock of the braid lead versions.
If I start on that scheme with my lack of electronics comprehension I will run into the problem of the diode layout for the reverse diodes on the subsidary heatsink plate and the appropriate number of diodes. I hope that can wait.
Now i have re-assembled 1 rectifier made out of 2. I used the AVO and the Edgecumbe Peebles for testing old diodes, the latter meter ONLY ON OHMS RANGE, not megohms with 500v. Unfortunately, the AVO has developed trouble on zeroing in 1ohm range though i did a subtraction and obtained readings of between 11 and 13 ohms vs infinity on the old Motorola diodes, just enough possibly-good ones.
and a few dud.
The failures have been confined to the reverse diodes. They are set out in 2 groups of 4, terminated on a central connector which links through to the forward diode assembly. Wish i could send photos immediately and link the Lincoln minimig 180c circuit diagramme.
Also, all failures were in 1 of the 2 groups. There must be something for me to learn in this matter.
All diodes were from 1988. The forward diodes on the other heatsink plate are in 2 groups of 5, the number had been increased from 4 as found in the previous year’s model I was expecting to find matching population.
Ah! There are 4 more reverse diodes on the ‘subsidiary’ heatsink!
The machine has been in an unheated farm building for 7 years and my workshop was pretty dismal prior to that, so I am not surprised at the failure.
Many thanks!
If you gentlemen have time and patience then I would like to understand more. Something of an adventure for me!
Late night again.

 

[Lincsnap180]

Huge thanks to Dragnet and Eddie again.

Ease of mounting is an issue after re-fitting pressfit diodes with delicate strap terminals very similar to those in Eddie’s first link

I have been looking at VS-85HF120 (and HFR) diodes, read the data sheet, checked dimensions but the graphs are beyond my ken. The ‘package’ seems to be designated DO 203 AB (DO5), arcane to me but the drawing and dimensions are ok.

Physical size of components is critical because the space ‘envelope’ in the machine is very restricted so that stud diodes of 25mm approx. height are maximum which can be accomodated.

Quantity of consistent components is a concern.

Price is an issue: if 22 pressfit diodes 50amp are to be replaced @ perhaps £3 each it seems reasonable if not cheap, if a smaller number of 85amp stud mount are fitted @ nearly £10 each then it looks more expensive but worthwhile if the machine is of reasonable quality.

Number of diodes is guesswork for me: there are diode groups 5off at 50amps therefore maybe the total current handling would be 250 amps, perhaps such a group could be replaced by 3off 85amp IF the total capacity is actually 255amps for the new group. Would it (by reversed reasoning) be necessary to use greater number of lower capacity diodes?

Another unknown is whether the existing heat sinking capability is sufficient to keep fewer, larger diodes within their safe temperature range if they are spaced more widely on 4mm aluminium sheet (ally fins could be tig welded onto the sheets and black vht paint used to augment cooling away from electrical contact).

It may be necessary to solder braid lead onto stud mount diodes because the VS-85HF120 (and HFR) diode version with braid leads are not stock items, but maybe that raises the issues of over-heating diodes before use and suitability of high quality audio speaker lead.

Following Eddie’s 5th link I have been reading another catalogue but found a handy stud mount diode (ds75-12b) is aleady obsolete! The replacement is @ £22, totally different package, and I have no idea about heat concentration/sinking.

I will investigate RIFA units later, this is a bit complicated for me!
Thank you again!