using new technology on old machines

[Mark J. Blair]

> On Jun 15, 2015, at 21:40, tony duell <ard at p850ug1.demon.co.uk> wrote:
> 
> Exactly. I don't do firearms at all (we have various IMHO ridiculous laws in the UK,
> but I do not want to start that debate)

Sorry I even brought it up; I was just using it as an example of the different specializations that each person might wallow in. Guns, religion, politics and text editor preference are often too contentious to discuss in polite company. :)


> But if you are going to repair/restore something then IMHO it makes a lot of 
> sense to have common spares around.

Agreed! But you generally tend to accumulate those spares *after* you have been involved in that particular area for a while. Coming into it from scratch, you might not even know which parts you're most likely to need. And buying every common-ish part that you might need is an expensive proposition.

> But common TTL parts, transistors, etc are used in many 
> machines, and if you are going to restore the real hardware you are (a) going
> to need them and (b) are going to need to now how they work so you can
> trace faults.

Right. So coming in from scratch, you might buy a tube of 74LS00 instead of just the one that you need to fix one board, and so on for many other common parts.

> One method that works for me is that if you are buying a fairly cheap part, buy
> 10 of them and put the rest in stock. Or more than 10 if it is something really
> common.

Agreed again! For example, the first time I had a Rifa paper-dielectric EMI filtering cap go incandescent on me (happened to be in a Tandy Model 12), I figured out the three or four kinds of much better poly film EMI filtering caps I'd need to replace them on sight in the Astec supplies that Tandy stuck in everything, and I bought lots of extras. But I don't have a single 2N3904 in my junk box, because I don't think I've had to replace one in the last 30 years, just based on the kinds of things I've been working on. So it's not my go-to part. Now, 10k resistors and 0.1uF ceramic caps... those things I use a lot. :)


-- 
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/