Re: Compters without printer port

Dear TOM caudle

I like a lot of what you are saying and yes, generally you have to be really "rough" to do permanent damage to a MODERN PC.

But many here use older PCs or Laptops which might not be as robust as something new(er)....

The point I was also trying to make, which you appear to have completely overlooked is that if something is pulling too much "source" current from a PP output pin AND the BIOS boot checks for such things as possible shorts on output pins (amongst other things!), then the PC may stop booting as a safety precaution, seeing that as a short.

The original poster has already said that with the cable removed it then boots....! WOW! this info must count for something....

Maybe a high voltage on an input pin can do the same thing, that is also possible.....

Whatever, the boot does not like the situation with the cable connected for some reason or another, but I am too far away to be able to prove exactly what it might be.....so I expect are you too!!

Not overstressing the PP in either direction is what makes things work ALL of the time. All you can really RELY on is a 7400 output capability, taking chances on anything else will often lead to problems.....

I mentioned the Opto isolators as many feel they are a good idea (if properly designed they are!), but I seldom see any PP to Opto designs that truly take into account the 7400 output characteristics....sadly.

For anyone like yourself with probably a lot of experience, not a problem, but maybe the OP is slightly out of his depth and asking for us to help him for that reason......I did not get the impression that you helped him in any way with what you wrote, unless he was as experienced as you probably are, then he would probably not have posted in the first place!!!

Try initially putting yourself in his position, then I am sure you/we all can help him much better......

What do you say to that?


Greetings from

Andy Mathison

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