Replacing capacitors in old TIG welder, and adding cooling unit.

[chy_farm]

Good morning gents,

I got an old but refurbished TIG welder last summer, but after giving her some inspection I found she needs some of her capacitors replaced with new ones. The seller/dealer said she got a lot of cleaning inside, seems it's true, but yet some hard-working parts are showing some signs of deterioration. It was fortunate to me that I was able to bumped into an engineer who has been working at a local welding school(may be it is operated local government officially). What he said was all very accurate in detail about the electrical functions of this machine, and the way he told was generous and gentle. So gradually some doubtfulness in my mind faded off, and got inclined to put trusts on his words.

He said in the early models of this set-up, he encountered several cases of issues on a set of capacitors on the very limited area of the circuit board, the power supply board.

Capacitors_MB_board_05_s.JPG

Area with red marking in above, and the said capacitors are the larger round stuffs with red arrows. He said these capacitors tend to get a lot of electrical stress when we use the welder in excessive duration of time with higher amperage, while others around them are not like that. Actually he showed me some data he has got when he has made examination on other capacitors, that tells the other stuffs have been working all right on this model.


Capacitors_MB_board_00.JPG

When I saw the top surface where you see the 'Y' marking above, these marking show no sign of distortion. (Incidentally in some bad cases this Y mark shows some rise upward, tells this part gets pressure inside. )

So I told him this fact, but he replied that still there is some possibility of deterioration in the capacitor which causes oxidation to the brazing area of the board.
So this words of his led me to the next attempt to remove these capacitors as below,

Capacitors_MB_board_03_s.JPG

and see how the colors of the 'land'.(they call the small holes with copper plating on any circuit board 'lands/land')
These lands, especially where I marked with red arrows has got some dirt around them.

Capacitors_MB_board_01_2.JPG

In the worst case, if we keep these untouched, these oxidation go farther deeper to the copper plating of the board, and finally invite disconnection to the part. Yet an examiner/user may not be able to find out where to be repaired, since the issue is undermined at the foot of the capacitors which looks pretty good at glance!

Capacitors_MB_board_06_s.JPG

Could you guys tell what are the new capacitors I replaced, they are all a tad smaller than the old. Small but has better durability to the load, the old bears 85 degrees Celsius, new 105 degrees.

to be continued...

Chy

[chy_farm]

I also made a check to the secondary power board of this welder, found some minor deterioration to the capacitors and resistors located near IGBT(Insulated Gate Bipolar Transistor) s.

Resistors:

reverse side looks like this, had some burn under these resistors.


This part seemed to be the worst, some sticky stuff had accumulated a lot of dust.




Capacitors:
Four bigger capacitors were removed and checked the holes;




(to be continued...)
Chy

[chy_farm]

I replace 6 of these original resistors that has been deteriorated with excessive heat, with cement resistors having larger capacity. Old ones were 3 watts, new ones are 10 watts, marked with red arrows here;


Amongst them two in the middle are capped with 'black hats', arrows show them;

This black hats are made of a new material invented at a domestic maker here, which has high heat conductivity useful when we need more heat radiation to electric parts.

This area has been the most heat concentrated area, so made an aluminium heat sink and added here.


After these replacement I tried adding a couple of cooling funs to this area.

(to be continued...)

[chy_farm]

The inverter boards to which I gave some replacements are on the second deck in this TIG welder, posting a pic showing its back side;

As this pic tells the second deck has a little room to the ceiling, and what's so worse there was not window on this deck.

These are what I added to it!

After these repair this welder does not get over heated at all.

Hope it can be of some help to your welder!

Chy

[Gadgeteer]

Well done! I've, also, brought TVs and VCRs back to life by replacing bad caps. Most of the time the caps were identified, due to leaking and swelling.

[bruce.desertrat]

Ugh. The Capacitor Plague plagues us all. Nice fix on that welder!

[Jerry4Truth]

Thank you chy-farm, that is some very useful information. Some I am sure to use in the future.

Jerry4Truth

[chy_farm]

Well done! I've, also, brought TVs and VCRs back to life by replacing bad caps. Most of the time the caps were identified, due to leaking and swelling.

Good afternoon Gadgeteer, thank you. Glad to know you know much about the same sort of things. Wish to learn some more from you too,
Chy

[chy_farm]

Ugh. The Capacitor Plague plagues us all. Nice fix on that welder!

Hello Bruce.desertrat, yes they sometimes do bad on boards, let's keep watching them! Thank you for your comment.
Chy

[chy_farm]

Thank you chy-farm, that is some very useful information. Some I am sure to use in the future.
Jerry4Truth

Hello Jerry4Truth, and good afternoon Sir. I love to see your avatar image here! Is this telling that you are one of the veterans? If so, I always pay greatest respects to them.
Thank you for your comment on this capacitor issues, but I really do not hope you got troubled with that sort of capacitor things in any machines there, lol.
Chy