OT Troubleshooting: Old computers with modern parts

[Tony Duell]

I actually don't see why this is off-topic, but anyway...

> The main problem I see with the current crop of PDP-8 clones/replica's today
> is lack of paper tape and other hardware at the time -- non volatile memory.
> I could get a cpu chip off people on this list but with out I/O like 
> paper tape
> or a modern replacement the  software for the CPU is very limited in what
> can run and what can future hold as mechanical devices wear out in time.
> I think we need to get mechanial minded people ( also a dying breed) to

\begin{rant}
Is that suprising? At least over here the only prople who seem to get any 
sort of respect are those who can kick a football or strum a guitar 
badly. Engineers, scientists, etc, are worthless. Heck, you don't get any 
friends if you'd rather spend an evening holding a logic probe rather 
than a beer glass
\end{rant}

Sorry, this is a sore point with me, and with most of my friends....

I nearly added a couple of books on metalwork / lathe operation to my 
list of recomemnded books for classiccmpers, but I thought I'd probably 
be flamed for being off-topic. 

Books like : 

The Amateur's Lathe

Various books from the 'Workshop Practice' series. 

And many others in the Camden booklist (and probably available from 
Lindsay Books).


Anyway, a small lathe is something that most classiccmpers should 
probably consider owning. Small meaning < 4" centre height or so. Even 
something like a Peatol (Taig) or a Unimat is enough to make a lot of 
parts for classic computers. I have a Myford Super 7, which is a bit larger.

A vertical slide is very useful becaue it lets you do small milling jobs 
too. Of course a proper milling machine is much better, but also a lot 
more expensive and takes up a lot more room.

I regard both the 3 jaw self-centring and 4-jaw independant chucks as 
being essential. Along with the tailstock drill chuck, a set of centres, 
a faceplate and a reasonable selection of cutting tools.

With such a machine (and skill which I don't possess yet!) you can make 
most small mechanical bits for your classic computers. Bearing housings, 
pulleys, bushes, spacers, spindles, etc. 

You can also, of course, use the lathe to make more tools. Not just 
things like pullers, drifts, etc (sometimes essential to do repairs 
without damage), but also things like that injection moulding machine 
that was mentioned a week or so ago. And that would be quite capable of 
making keycaps, switch toggles, etc.

Is this off-topic? I don't know.

> help where electrionic/computer stuff does not cover forgotton techology.
> Sooner or later Epay will stop having old devices like TTY's and we will
> have to a) Hoard them, b) Let them wear out c) Rebuild them d) Forget about
> them.
> Take your pick ...  I favor c but I don't have the skills.

I favour (c) too. To me, not having the skills is a good reason to start 
learning...

Let's be honest. You don't _depend_ on your PDP8. You are not going to 
die, or be unable to afford food, or whatever if it's down for a month or 
more. Which means that if it takes you a month to get the skills to make 
the part you need, well, that's part of classic computing.

I would recomend trying to find (or make?) an optical paper tape reader. 
They're kinder to the tapes, and they have many fewer wearing parts in 
them. 

I am, perhaps, lucky. I rescued 4 or 5 Trend paper tape readers about 10 
years ago. These are very simple mechanically (and the eleectronics isn't 
much worse!). All the parts likely to fail are either standard (ball 
races) or can be made on a small lathe. In fact the part that fails most 
often is the illumination bulb, and that's a standard 12V car bulb in 
most of them, and a 24V lorry bulb in the others.

I wouldn't fancy trying to make some of the parts from, say, an ASR33 at 
home, but it's suprising what can be done if you have to....

-tony