Yo! Scott:
Thursday June 12 1997 18:42, Scott Christensen wrote to Bill Cheek:
 SC> Caught your memory mod in Monitoring Times this month.  I would make
 SC> the circuit simpler: Pull up pin 19  - just like you said...
Well....my approach pulls it down....and switches it high; not only a 
diametrically opposed physical issue, but also a philosophical one.
 SC> Put a 10K resistor from pin 19 to 24 - the +5 V line... Put the
 SC> switch between 19 and ground. It saves a component, cuts the "flying
 SC> tie points" by 50% and makes for a neater installation. You are free
 SC> to distribute this mod - it's standard industry practice. I might
 SC> place a .1 uFd chip capacitor between 19 and the pad below it if I
 SC> were really going to get fancy...
Quite understandable, tolerable, and perhaps even superior, depending on the 
point of view.  Except for one wee little thing.    :-)
I take the design of a mod and its "do-ability" into account before 
publishing it.  If I design it for a pro, that sets one design approach.  If 
for a neophyte, then the approach can markedly differ.
In that particular audience, (Monitoring Times), you never know who's going 
to grab a welding torch and go to town.  So.........??????
So I design for least risk to the equipment, given the hands of an imbecilic 
idiot who doesn't know a resistor from a resister.  Specifically in this 
case, the target radios are not widely used by serious or advanced hobbyists. 
They're designed for the yuppie; the old fart; and entry-level weenies.
Pulling pins UP is a lot riskier in terms of ESD than in pulling them 
permanently low.  Switching low is also risky in terms of a catastrophe if 
the pullup wasn't done right.
My "extra part" is a safety valve and a troubleshooting aid in the even 
anything goes wrong and someone whines for tech support.  And whatever they 
did wrong, there is less liklihood of unreversible error than in your method, 
"standard" or not.  Sometimes, "standards" are just wrong.  :-)
Think about it.  A pin that floats high and is accessible to the outside 
world, even if by a switch wire.....is in grave jeopardy.  Pulled permanently 
low and switched high via an isolation resistor reduces risks, elevates the 
margin of error; and still accomplishes the intended result.
Lastly, the skilled pro who knows what he is doing typically needs only an 
idea; not step by step nursemaiding.  The rank novice needs to be handheld 
and guided to not only success, but also safety in the event he can't 
assimilate what he reads.
In a word, I have been dealing with skilled pro's and rank amateurs in 
electronics hacking and re-engineering since the early 1970's.  If a mistake 
can be made, I've seen it.  And when mistakes are made, I hear about them and 
have to provide technical support to get the poor sap back up and running. I 
am, therefore, motivated not only for his sake, but mine as well, to keep the 
fool from porking himself (and me) in the first place.
Therefore, whenever possible, my procedures and designs take into account WHO 
might do them.....and where ever warranted or possible, I'll include fuses, 
circuit breakers and other safety considerations in the natural course of a 
design.  It may sometimes mean the long way around, but since 1988 when I 
started hacking and publishing for scanners, the number of "basket cases" as 
a result of people following my instructions is ZERO.
The number of basket cases as a result of skipping steps....or doing it the 
"professional" way is several, that I know of.  Out of over 1000 CE-232 
Scanner/Computer Interface Kits I've sold, only two cases of ESD-possible 
failures have come to surface.  And none at all with respect to all my other 
mods.
Fundamentally speaking, there is a method to my madness.....and have you ever 
seen an electronic hack writer with FEWER CAVEATS than me?  I rarely write a 
caveat, and when I do, it is usually a LEGAL one....relative to LAW, like 
listening to cellular conversations.  I rarely write a caveat that "if you 
screw up, you're on your own....."
Ummmmm......I don't -=NEED=- to.
:-)
Bill Cheek ~ bcheek@san.rr.com
Windows 95 Juggernaut Team ~ Microsoft MVP
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