Lil' Blackbox

General => Hardware => Topic started by: Rx7man on April 29, 2018, 04:34:16 PM

Title: Oh Joy.. reverse engineering
Post by: Rx7man on April 29, 2018, 04:34:16 PM
I have a problem with my welder.. suspecting the high power board.. AC generator works, no weld output though, mechanics are fine,.. and of course schematics are "proprietary" and unavailable.. Board has about $200 worth of components, certainly could be designed as a 2 layer with a few vias (no vias, thankfully, that would make tracing harder)

3 layer board, 55 resistors, 25 capacitors, 40 diodes, few rectifiers, half dozen high power transistors, 4 optocouplers, couple op-amps, and about 30 connectors.. I'm just lucky it's a very translucent board and I don't have to probe everything, I can see the center plane through it, and mostly just fine traces there.

Once I get it drawn out I can start troubleshooting and see if it's the control circuitry or the power section that's not working
Title: Re: Oh Joy.. reverse engineering
Post by: hakcenter on April 29, 2018, 05:03:13 PM
omg is that 45 degree angles in the schematic phase ? noooooooooooooooooooooooo
Title: Re: Oh Joy.. reverse engineering
Post by: Rx7man on April 29, 2018, 06:35:52 PM
yes, yes they are.. I'm trying to make the schematic approximately like the board, or I'll never see it through.. maybe when I'm done I'll make a second copy where I organize everything nicely... and don't have wires going through devices.  As you see, for now, with some of the devices they're just black boxes that look like the physical device.. later I'll fix that too.. maybe.
Title: Re: Oh Joy.. reverse engineering
Post by: Rx7man on April 29, 2018, 07:14:44 PM
Oh, yeah, I was told it's a 3 layer board.. they're wrong, it's 4 layer..
Title: Re: Oh Joy.. reverse engineering
Post by: Rx7man on May 01, 2018, 09:50:28 AM
I'm grinding away at it.. nearly done.. Had to desolder 2 of the control relays and an 11 pin transformer..  Really hard to trace the circuits on the center layers if there are devices with continuity.. (hence the need to desolder) they also use a VERY high temp solder, so it took a lot of solder wick, had the iron cranked right up to 500F, and to top it all off, the devices/board have conformal coating on them which makes them hard to work, and it glues things down.. Well, I see the finish line at least!
Title: Re: Oh Joy.. reverse engineering
Post by: Rx7man on May 02, 2018, 12:12:12 AM
OK.. Does this look better?  that was a dozen hours work.
Title: Re: Oh Joy.. reverse engineering
Post by: hakcenter on May 02, 2018, 08:05:16 AM
jusss
Title: Re: Oh Joy.. reverse engineering
Post by: Rx7man on May 05, 2018, 12:36:36 AM
hows this?
Title: Re: Oh Joy.. reverse engineering
Post by: hakcenter on May 05, 2018, 08:24:58 AM
Followable
Title: Re: Oh Joy.. reverse engineering
Post by: Rx7man on May 05, 2018, 11:03:01 PM
I was debating whether I should lay it out with labels for some of the common stuff or actually wire it... couple of them were a pain.. no way to make them not cross all the way across the board