Electrical Components...

[Tpt life]

What’s likely to fail on this board such that when it’s cold, it will fail to operate? It will try, then cycle short. A bare 30 seconds with a hair dryer and it will work again. 

[Tom King]

Sounds like a transistor.  The next time it does it, try directing the heat just on those these black transistors on a diagonal line between the wires on the left, and the middle one of those three white things on the right, and see if that does it.  They look to me like transistors in the picture, but it could just be the angle, and they could be capacitors.  If those are capacitors, look for diodes.  If it's the main IC, you probably need a new board.

[Tpt life]

With an area to focus on, does this well lit closeup of that zone help you confirm anything? Three wires exit each. 

[Tpt life]

That was stupid. Wires unplugged, all visible. Should have started there. 

[Tpt life]

According to the wiring diagram, the plug bundle in the lower right was upside down from the factory. It ran for decades so I don’t know if it matters. 

[Gary Beasley]

If cold is causing it then likely its a poor connection on the circuit board thats disconnecting as the metal contracts. Look for loose connections, even a little wiggle is suspect. Semiconductors generally dont  fail from the cold, they actually like it. One test for bad components is spraying with a freeze spray to see if it starts working again while cold.

[wtnhighlander]

Agree with Gary, a poor solder joint is more likely to open from cold contraction.

Although, those white cubes to the right are electro-mechanical relays. Their contact might exhibit the same symptom.

[Tom King]

One easy test would be to switch those relays around to see if it did anything different.  Those black things, with one flat side, are transistors.  There's plenty to cause the problem.  Schematics and a way to measure voltage would be the only sure way.

[Tom King]

A transistor is sort of like a little switch.  It has three legs.  One is hot coming in from somewhere.  When it gets a signal, it sends power another way.  I expect each of those transistors sends power to one of those relays.  Relays use a small electrical current to turn on a larger demand for something else, like a motor, or light.

If one of those transistors shrinks enough from the cold to stop sending that signal to a relay, something won't work.

 

[Tom King]

It pays to have good help.  Here are pictures of a couple of friends of mine having fun troubleshooting a board in one of my welders.  One is a retired department head at NASA, and the other works on boards all the time, as well as other really complicated stuff that goes into space.

They found the problem was an 80 cent transistor, rather than me having to buy a $538 replacement board.  Transistor on order.

I was some help.  I held the light, and helped trace the schematics for the next part we were looking for.  In the first picture, they're prepping the soldering iron. The tool nearest in the second picture is a spring loaded solder sucker.  They were taking out the bad part.

 

[Tpt life]

What do they call themselves, the people that fix this kind of thing. Does anyone do that as a business anymore?

[Tom King]

Electronics Technicians.  There are plenty of places that do it for a living.  I googled the number on that board (miller 210381), and all sorts of places came up, as well as the manufacturer, with prices listed for repair, and replacement.  Average repair price for that Miller board was $238.  It's a Lot more complicated than your board.  Get the model number off of it, and Google the manufacturer name, and model number.

[wtnhighlander]

@Tpt life, flip the board over, and look at the solder joints. They should be smooth and shiny. If you see some that look dull or lumpy, it is a good indication that it wasn't heated properly at assembly time. The board Tom pictured is obviously complex enough that it waa probably "floated", essentially dipped into a pool of molten solder. Yours looks simple enough that it MAY have been soldered by hand. Poor joints are relatively easy to spot, and simple to fix. To send even a simple board out for diagnosis and repair is likely to cost 50% or more of a replacement. If you can identify a bad joint, chances are good that one of the strip-mall holes-in-the-wall that advertise cell phone repair can re-solder it for a few bucks.

[Tpt life]

I think I can re-solder unless it it more complicated than tinning wire. I know heat needs to be mitigated to not damage the wafer board. I had the board out, so know it comes out easily. 

[Tom King]

Here is the part we need for the welder board:   https://www.ebay.com/itm/1pcs-TEXAS-INSTRUMENTS-TI-TIP36C-25A-100V-125W-PNP-TO218-Transistor/153974338349?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

You need a small soldering iron for board parts, and a thing that sucks the solder out once it's melted, to take out the old part.  I had an old iron from when we built Heathkit kits, when we were teenagers, but it was too corroded to work, even though it heated up some.  The gun, and solder remover were cheap tools I ordered direct from China, off ebay.  The soldering iron was a little bit aggravating to get going, but once the tip was well sanded, washed with flux, and tinned with some of the very small rosin core solder, it did fine.

Those guys are used to working with the best tools, like a vacuum pump to desolder, but they made out fine with my cheap tools.

[Immortan D]

When something works, then stops working after a while, then again, the problem is often in the capacitors. I see 3 of them on your board, the black things standing upright. But in order to test them accurately with a multimeter they have to be removed from the board... Bad capacitors often have a bulged appearance, I can´t tell if yours are OK from the pics.

That said I wouldn't mess with a power supply board like yours, I would just replace it or have it inspected by a technician.

[Minnesota Steve]

How cold is "cold"?   Below freezing?   It's possible that the relays over time get condensation inside them and this is freezing.

 

[Tpt life]

Freezing? Yes, barely. This was a garage door opener that I likely could have fixed for pennies with the right friend. With time investment calculated, I bought a new one with more bells and whistles. That board goes out with tomorrow’s trash. 

[RichardA]

1 hour ago, Tpt life said:

Freezing? Yes, barely. This was a garage door opener that I likely could have fixed for pennies with the right friend. With time investment calculated, I bought a new one with more bells and whistles. That board goes out with tomorrow’s trash. 

I don't have a garage, so I'm asking a dumb question:  Garage door openers, open and close the garage door.... Right? What "bells and whistles" can there be for a tool that does two things?

[pkinneb]

6 minutes ago, RichardA said:

I don't have a garage, so I'm asking a dumb question:  Garage door openers, open and close the garage door.... Right? What "bells and whistles" can there be for a tool that does two things?

Lights, Wifi enabled, locks, etc

[Tom King]

That's the best fix for an old garage door opener.  I thought that was probably what that board was, with three functions- up, down, and lights.

My transistor came direct from Japan on Friday.  We put it in Saturday, and in a little while, we were back to melting MIG wire.  A replacement board was about $500, and a new welder $2800, so this was worth the time.  Now, I need to do some work on my loader bucket, which is worn thin on the back, bottom edge.

[RichardA]

3 hours ago, pkinneb said:

Lights, Wifi enabled, locks, etc

I'm old , who knew?

[Coop]

You have old company!