on the occasion I have to remove solder mask to hack a pcb, it seems to be indestructible substance and peeling it of ought to make you king of England but I guess if it happened to flake off it would in the most inconvenient place :)
-Lasse
You should have bought a Volkswagen!
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Yeah, a "clean" Diesel :-)
I can't complain. The Toyota is now 20 years old and my wife drives it shorthaul all the time. 2-3 miles, then 2-3 miles back. That's the worst mode of operation for a car and its catalytic convertor. I am surprised it hung on this long. The good news is that even a California version of the convertor can be had for much less than $200 and on this model it doesn't need to be welded in, it's bolt-mounted.
My car (Mitsubishi SUV) is almost as old but I do all shorthauls and even 50-milers by bicycle. So it gets to see mostly longer trips, and very few at that. The result is that with similar technology it always passes smog checks with huge margins.
-- Regards, Joerg http://www.analogconsultants.com/
Well, I finally dug up some real info about the fault. It wasn't the FET, it was actually the input capacitor that had the square pad at its + end and the burn marks were between that pad and a nearby fill. Mains voltage here is 240V, so the cap would have had about 330V across it (and across the 0.7mm gap). Ouch.
All should be obvious from this image:
Quote from an email from the manufacturer (who didn't realise we were on the CC: list) - ?I find it hard to believe we have a spacing problem on the [redacted] at this point, so likely they did something to these things. Not sure what off hand though."
Regards, Allan
That is in the IPC standards AIUI (IPC7351B and forthcoming IPC7351C).
-- John Devereux
;) (I've just reread that part of the Morte d'Arthur. Good stuff--I love Malor y but Chretien de Trois is just too French.)
Just like old wallpaper!
Cheers
Phil Hobbs
Or this decorative wall paneling which unfortunately was installed in our house many moons ago. Supposedly "forever" and now the occasional barbed nail lets go. The only way to tuck it back onto the drywall is a screw or two and that looks yucky. So in my office I have some areas where it begins to gap. Harumph!
-- Regards, Joerg http://www.analogconsultants.com/
Oh yeah, a major design blunder.
I'd have responded with an attached excerpt of the applicable standard which for sure was violated :-)
-- Regards, Joerg http://www.analogconsultants.com/
Looks more like the current sense resistors failed. First one, then the other.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
The photo shows three parallel low value resistors, all of which have likely failed open circuit. The last to fail arced on it's own carbon track and current flow, creating the mess. It's possible that residual arcing occurred to the cap lead through the carbonization.....but the point is that this is not a root cause, unless (and only if), after their replacement and repair of any damage that voltage surges on this node might induce, the unit powered up and ran normally.
The resistors are more likely to have been overstressed by a preceding fault, with component failures that have not been located by thorough probing.
It is also unlikely that this was the last component in the fault path to go open, as the adjacent parts would be expected to arc over once the parallel parts cleared or burnt open. Some other component, possibly even an intentional limiter like a relay, breaker or fuse opened before this could happen. A power semiconductor bonding wire is the most common unintentional fuse.
RL
Liquid nails (or other brand of panel adhesive). then tack or prop for a few hours.
-- \_(?)_
Ha!
I've returned various new assemblies that were just poorly designed or had crappy assembly. Nobody has ever admitted any sort of fault and they (different companies) always take them back and no doubt sell them to somebody else.
At trade shows PCB assembly houses love it when I drop by, examine and ask why every demo board is a complete reject. Very few places actually demo stuff that would have passed even cursory QC checks.
Other places are still showing off mid 1990s type boards, and I still see ISA computer cards to this day.
be
ory but Chretien de Trois is just too French.)
Chretien de Troyes. Troyes is a town in France (and I've been there) and if Chretien hadn't invented Lancelot and the Holy Grail, Malory wouldn't have had much to write about.
The Arthurian legends seem to have been originally Welsh and Breton, and a lot of the original heroics involved pig-stealing.
-- Bill Sloman, Sydney
Cool. Thanks. It looks like about 8 volts/mil is good, which would be
150 mils for 1200 volts. My 2SK4177 transistor almost passes!-- John Larkin Highland Technology, Inc lunatic fringe electronics
Tried that. Eventually it'll rip some sort of cardboard off of the drywall. The only thing that helped was to drill and countersink behind a desk or picture and screw into the drywall, hoping that the gypsum won't crumble.
-- Regards, Joerg http://www.analogconsultants.com/
How about a decorative geometric pattern of fancy screws?
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
The WAF would be way too low.
-- Regards, Joerg http://www.analogconsultants.com/
Don't you own the Man Cave?
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Theoretically yes, but only theoretically. She'd be embarrassed for me if I have guests and the place would look too redneck. When we dated she almost freaked out when she realized that I had soldered on a torn button on my shirt, using stripped wire.
My real man cave is open air, my mountain bike. That is built out just like I wanted it.
That's a fairly clean condition. Sometimes the whole thing is brown and dripping mud.
-- Regards, Joerg http://www.analogconsultants.com/
Ah, that explains the vertical stripes on your bod, front and back.
Skiing doesn't do that. Usually.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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