On 2008-01-31, Jon Elson wrote:


Ignoramus19508 wrote:
On 2008-01-31, Don Foreman wrote:


In fact, this is what I like about these boards, they are 1) very low
tech and 2) easy to repair due to good part placement 3) easy to
identify components, which look mostly off the shelf.

My repair was, obviously, the most trivial kind, but I appreciated
repairability of these boards.

I had to dig into my 800+ Pound Lincoln square-wave TIG 300 machine,
and old-school transformer AC/DC constant-current power source with
SCR phase control. Well, the power components are mostly brazed,
welded, etc. and then everything bolts together. But, there are
several fairly large circuit boards in it. There is a main control
board that pretty much covers the entire back of the control panel,
and then a power supply board, a phase controller board and a safety
board, as I recall. Yes, everything is off the shelf, resistors,
caps, ICs, pots and switches, etc. The shield gas post flow timer
was bad, and I had to trace the wiring and replace it. As the damn
boards are all conformal coated, I DID use my Pace tool to desolder
it, it does a much better job when the going gets rough.

By the way, grinding dust is the reason for conformal coating.

i