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How do I wire wrap used back planes to build a pdp8 straight 8?

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rorypoole

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I have never done any wire wrapping but will be getting some used PDP8/a and PDP12 back planes to build a pdp8 straight 8, where is good to get wire wrapping tools and wire?
and where is a good information on how to do good wire wrapping?
 
RS components or Farnell/CPC would be the place to start. They may be more expensive than other places - but they have the stock of items when you want them and can therefore deliver at short notice (usually the next day). You need a stock of all sorts of colours if you don't want a major headache later in trying to debug your wiring!

Wikipedia "http://en.wikipedia.org/wiki/Wire_wrap" would be the place to start to learn from. But (in my experience) you need to get hold of a wire wrapping tool and have a go yourself before embarking on a major project. This is an art not a science!

There are cheap 3-in-1 manual strip/wrap/unwrap tools, more expensive manual tools and automated wrapping tools. I have the cheap tool because I don't do too much of it these days. However, you get all sorts of cuts and grazes on your hands! If I was doing a lot of wrapping (like some of the guys at work) I would invest in the better tools.

Where are you in the UK? I am in Worcester. If you want to see and have a play with some tools you are most welcome if you can get to Worcester or Gloucester.

Dave
 
daver2 said:
RS components or Farnell/CPC would be the place to start. They may be more expensive than other places - but they have the stock of items when you want them and can therefore deliver at short notice (usually the next day). You need a stock of all sorts of colours if you don't want a major headache later in trying to debug your wiring!

Wikipedia "http://en.wikipedia.org/wiki/Wire_wrap" would be the place to start to learn from. But (in my experience) you need to get hold of a wire wrapping tool and have a go yourself before embarking on a major project. This is an art not a science!

There are cheap 3-in-1 manual strip/wrap/unwrap tools, more expensive manual tools and automated wrapping tools. I have the cheap tool because I don't do too much of it these days. However, you get all sorts of cuts and grazes on your hands! If I was doing a lot of wrapping (like some of the guys at work) I would invest in the better tools.

Where are you in the UK? I am in Worcester. If you want to see and have a play with some tools you are most welcome if you can get to Worcester or Gloucester.

Dave
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I dont need to do the wire wrapping till I have a set of flip chips ready, and the straight 8 case steel work done.
I am in the UK, and will be close to Worcester in July to August when I am volunteering up there.
what problems should I look out for, as I am new to wire wrapping ?
I will look for a cheap 3 in 1 tool.
 
The mechanics are quite simple. Strip the correct length of insulation from the wire (you can measure this from the tool). Insert the stripped wire fully into the tool (it should go all the way inside the tool complete with a small amount of insulated wire) and perform the wrap in one nice, steady and continuous motion. You need to apply just enough force so that the wire wraps neatly on the posts - but not too much so that one wrap slips over another. You should have a single winding of insulated wire around the post in addition to the normal stripped wire. This is important as it prevents the wire from fracturing easily in the future.

After you have performed the wrap, look at it critically in good light. If it is not "right" take it off and do it again. This will prevent major headaches later if a wire breaks on you.

Only work in good light (I find daylight the best) and set yourself a maximum target time to ensure that you do not become too tired.

Have a schedule of wires written down and tick each one off as you go. This should prevent you from accidentally missing one out.

You will find with the 3-in-1 tool that the sides of your hands and your palm will get sore (depending upon the amount of wrapping that you do). I used to have a separate wrap and unwrap tool that I used. These had "proper" handles on them which meant that damage to your hands was a minimum.

Dave
 
I suspect (looking at the photograph at "http://www.pdp8.net/pt08/pics/pt08bp.shtml?med") that the backplane wire-wrap pins may be a much larger gauge than current electronics types (0.025" square).

We use the larger gauge at work (heavy electrical) so I shall ask the question.

Dave
 
These posts look more like what the telcos used or used to use. AWG 26 wire on large posts. Supplies should still be available, given their wide use. Telcos used a lot of the semiautomatic wrapping tools from Gardner-Denver for field use, where you squeeze a trigger to spin the bit. Makes very nice looking wraps but gets very tiresome if you have a lot of wraps to do.
 
A comment for the original poster: pdp8/a backplanes are going to be extremely painful to make use of. The H803 cardedge to wirewrap connector blocks are wave soldered to a circcuit board that provides the bussing. You will need to reheat large portions of the circuit board to remove the H803s.

Lou
 
Lou - N2MIY said:
A comment for the original poster: pdp8/a backplanes are going to be extremely painful to make use of. The H803 cardedge to wirewrap connector blocks are wave soldered to a circcuit board that provides the bussing. You will need to reheat large portions of the circuit board to remove the H803s.

Lou
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I have a hot air solder rework station, and a drastic shortage of parts, I am waiting for for the first part to arrive from the usa, a R111 flip chip.
I may use the PDP8/A shell for I/O expansion?
 
I think the wire size is 20 something gauge for the PDP8 and 30 gauge for later pdp back planes
 
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This seems to be the definitive document on the wire-wrapping subject "http://www.soemtron.org/downloads/decinfo/logichandbookmar67.pdf".

See page 243 for wire wrapping tools. I wonder if they are still current products...

Dave
 
Would it be a problem to use non silver plated solid copper insulated wire for wire wrapping?
 
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I don't think so, as long as the wire is the same as the one made for wirewrap.
Does your pins have a coating? If so, what type?
 
This is going to be so much work, you should not skimp on the wrap wire. You should spend the money and use silver plated wire. You see, the silver promotes good contact where the wire is squeezed against the corners of the wrap posts. The pressure there is extremely high and the layer of silver "flows" nicely to ensure a high quality contact that will stay low resistance for a very long time.

Here in the US, even the wrap wire sold at RadioShack (like Maplin in the UK) is silver plated. (And I use RS wrap wire...)

Lou
 
rorypoole said:
I have never done any wire wrapping but will be getting some used PDP8/a and PDP12 back planes to build a pdp8 straight 8, where is good to get wire wrapping tools and wire?
and where is a good information on how to do good wire wrapping?
Click to expand...

Why not build your own omnibus PDP-8a with those PDP-8a backplanes? You can even get peripherals for those slots!

I don't quite understand the fascination of trying to clone a straight-8. How many ~years~ do you expect to work on this project?
 
tingo said:
I don't think so, as long as the wire is the same as the one made for wirewrap.
Does your pins have a coating? If so, what type?
Click to expand...

I dont have the back plane parts yet, but some were wire wraped so maby silver plated? and the others where soldered so lead/tin coated.
 
AK6DN said:
Why not build your own omnibus PDP-8a with those PDP-8a backplanes? You can even get peripherals for those slots!

I don't quite understand the fascination of trying to clone a straight-8. How many ~years~ do you expect to work on this project?
Click to expand...
I like a chalenge and building a computer with no IC's is a great one, its not the same just pluging some card in, and I am planing on having my PDP8 working by the end of the year.
 
Lou - N2MIY said:
This is going to be so much work, you should not skimp on the wrap wire. You should spend the money and use silver plated wire. You see, the silver promotes good contact where the wire is squeezed against the corners of the wrap posts. The pressure there is extremely high and the layer of silver "flows" nicely to ensure a high quality contact that will stay low resistance for a very long time.

Here in the US, even the wrap wire sold at RadioShack (like Maplin in the UK) is silver plated. (And I use RS wrap wire...)

Lou
Click to expand...
I have some solid hook up wire and its plated, how can I tell if its silver plated or solder tinned?
 
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