I was guilty in my first month or so of servicing video games (back in the 70's) of plugging in a board while the power was on. This board had a 115VAC relay and, um, well..., it didn't survive the experience. This is back in the days when Pong was a big deal (B&W of course!) and the games sold for $4,000 (Yup, that's $4K Canadian, back then worth a bit MORE than the US$) so I had to spend a week replacing all the IC's (ALL!) to get it running again. Now, of course, I never plug a part in backwards. Really. "What Never?" "No Never!" "Well hardly ever..." (Gilbert & Sullivan) Clay is right, it is hard to blame the part for our screw-ups, BUT I tried! (running for cover now ;-)... Happy Ho-Ho's! John :-#)# At 03:02 PM 12/12/00, Clay Cowgill wrote:
I do find this a little silly. EPROMs will die if you plug them in backwards. PCB's will die if you reverse power and ground. This really shouldn't be any big news to anyone on this list... ;-) I do have an immediate solution that requires no modifications to the design though-- Don't do that!
I've sold lots of those 284's and 285's since 1998 and have had *maybe* a quarter of a percent of the total come back for repair (for *any* reason), so I'm really not inclined to modify my PCB design or hand-add a diode to every one. It's the 90:10 rule (or in this case the 99.75:0.25 rule :-).
Kev's not quite right on one point though either-- they can be fixed just fine. I just have to do it... They're $7 each plus shipping if you smoke one.
(I must confess that this really is perplexing to me. I mean, c'mon-- at my "real job" if my engineering technician complained that some part dies when plugged in backwards you can be pretty sure I'm not going to be blaming the part!)
-Clay
-----Original Message----- Date: Monday, December 11, 2000 8:06 AM Subject: Re: Pac repair using a chip comparitor
Mark's devices will die also if plugged in backwards...takes about an hour or more to replace the IC's, same as the original...perhaps we could ask both Mark and Clay to put in a 1N4005 diode across the Vcc and Ground so IT shorts out if installed backwards and not the board...sort of a Silicon Suicide device...
John :-#)#
At 11:16 PM 12/11/00, Kev wrote:
http://users.erols.com/mowerman/bugtrap.htm
pic & small write up of the Bugtrap.
Word about Clay's most excellent products (Vram address or Sync bus), plug them in backwards & they die. There is no fixing these. Mark Spaeth produces a replica of the original boards with TTL components that are repairable.
Personally I'm not too impressed with the Fluke 90 thingy, but maybe I haven't spent enough time with it yet.
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