RE: Pac repair using a chip comparitor

It is a very difficult part of product design, and there are different
philosophies regarding user mishandling. For parts that are nearly always
soldered on to boards, you don't need much protection against improper
insertion because machines will typically be putting them together, or
engineers that really understand the consequences of putting a part in
backwards are handling them. However, if the part is commonly stuck in a
socket, attached, moved around, unattached, then some sort of protection or
guide is many times used to prevent the accidental improper installation.
For example - keyed connectors, or a simple fuse. A person designing test
equipment that will be used by attaching to electronic devices also might
want to consider the typical user of the equipment probably does not have a
college degree, or might be in a hurry, or one of several other reasons
where a simple accidental backwards plug in, or off by one pin might happen.
So in the end if you can't design it so that it can't be plugged in wrong,
(like a keyed connector), you might want to design to minimize the damage,
and/or make the repair much more simpler if that happens, (like a fuse or a
simple diode protection).

My first job, getting out of college was with HP, and thats where I may have
picked up most of that.

Dale

-----Original Message-----
From: John Robertson [mailto:jrr@flippers.com]
Sent: Monday, December 11, 2000 1:23 PM
To: TechToolsList@flippers.com; TechToolsList@flippers.com
Subject: Re: Pac repair using a chip comparitor

Are you using proper static handling techniques for these parts? They are
static sensitive and sometimes people forget to ground themselves before
plugging a part in. Heating season has started and that kills more
boards...I know we usually manage to kill a board every year about now...

The price of $7 is extremely reasonable to repair those devices. The fact
that they are a programmed GPLA makes them very reliable and compact. I
would much rather keep a spare or two of those on hand then try to service
the older style boards. They take much too long to troubleshoot. And
normally the repair procedure is to replace all the TTL.

I bet Clay would sell the IC separately, but that might void the $7 repair
warranty...

John :-#)#

At 09:57 PM 12/12/00, Kev wrote:
>I wasn't blaming the part for the fault of backwards insertion. My dismay
>is that Clay's device is not repairable at all by anyone other than him.
>
>What happens if Clay doesn't want to service the devices? This has already
>happened in the case of the Multi Pacs.
>
>Look at what great lengths people have gone to decrypt, dechipher & reverse
>engineer arcade stuff now for the benefit of all. I can understand Clays
>intention to protect his work but it negates my ability to repair it.
>
>I've had another unit of Clays fail, a Sync Buss Controller that I know
what
>not plugged in backwards. The only thing I could find was a stuck data
line
>but I don't understand how this could blow out the chip and I know it
wasn't
>a short to higher voltage as I troubleshoot with +5 only until the board is
>up & running then finish the audio section, then do AC.
>
>$7.00 is a reasonable price for a repair but if I have an option for an
>equal replacement part that I can repair versus a part that I must ship out
>for repair, the choice is clear.
>
>To a non-solderer the Clay part & repair service is probably a good deal
but
>your are dependant on a soul source provider/servicer.
>
>I'm happy to have an option now with Mark producing TTL style replacements
&
>if I get strap down holes in the next revision I'll be estatic.
>
> > 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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other
> > questions, comments, or problems to jrr@flippers.com.
> >
Received on Tue Dec 12 09:40:27 2000