CPC 464 mainboard dimensions mismatch

[kanken6174]

Hey everyone,

So currently i'm trying to make a pcb that would fit within a 1st gen 464's chassis, i've found the following scan of a 464's motherboard:



Now it's very helpful, but the dimensions cited on the wiki just don't match:
https://www.cpcwiki.eu/index.php/Mainboard_Versions

CPC464 version 1 (original)

• Size: 405x155 mm

Now if i measure it based on this info, it doesn't quite match:


So is there something wrong with the wiki? Is there any point of reference someone would know on this board that would help me measure everything else?

Any answers appreciated

[robcfg]

You cannot measure the board directly as it's way bigger than a regular A4 scanner can do at once, so the images are slightly deformed.

If someone has a 464 board at hand, they could give you the right measures.

What measures do you need exactly?

[kanken6174]

 What i would need to make my board would basically be a mechanical drawing of that mainboard, including the board outline and hole distances/diameters... so unless this exists somewhere and i've missed it it's probably going to be difficult for someone to give me all the measurements one by one...

But if the measurements cited on the wiki are exact and correct, i guess i can always try to deform the image to match them... even roughly

[kanken6174]

Since i have the chassis coming in today (in theory), i might just use the chassis as a reference by cutting some paper to match it perfectly and *then* scan that and turn it into a cad drawing, that could work... 🤔

[robcfg]

Have you checked the service manuals?

[SerErris]

I can do some measurements today. I would actually only measure the holes in real world. That is what is important. Also the points where the ports are located are important. Everything else does not make any difference.

So that is 9 screw holes and the two big holes, as the chassis is going through them and then all the connectors.

Let me measure it today and also I can try to scan it on my A4 scanner again, but it will probably not be better than what we have today.

What you can do as well:
In the service manual you have a full shot of the PCB. You can try to work with that as your base and check if then the measurements do make sense.
/Edit: Checked the service manual. You cannot see the screw holes and not the edges of the mainboard in any way. So not a good reference.

[robcfg]

The solder sides may have less distortions than the component sides, for obvious reasons.

[Deevee]

Maybe one of my 464 is first gen, but not sure. I'll check that later today.

[kanken6174]

Have you checked the service manuals?

I hadn't! This seems to have some old style mechanical drawings for the main pcb i can work off of, thanks for the heads up! It's not perfect but already better than just the deformed pictures...

[kanken6174]

The service manual's drawings are also not excatly right compared to what the wiki says hmm...

[SerErris]

Okay, here is my scan.

My scanner will not be able to produce a sharp image as it is to far away from the glass to get a sharp image. However the size should still be correct.

It is a MC0001A PT NO Z70100

You cannot view this attachment.

[Bread80]

A couple of suggestions:
* Edge connector dimensions can be found in the relevant datasheets. The tolerance on these is pretty tight and going of measurements is unlikely to give the required accuracy.
* If I understand correctly you have a CPC case available. I'd recommend measuring the required mounting hole centres etc. from that rather than a board. And probably various other measurements are better made from the case rather than the board.
* Standard IC pin spacing is 2.54mm (and edge connector pin spacing). This can be useful for dimensioning. If doing so use a length of as many pins as are available and scale from their. The accuracy of measurement from a single pin will be poor.

[SerErris]

Here are the measurements:

Of cause all on the backside, so you need to mirror it for frontside (or upside) calculations.

You cannot view this attachment.

[SerErris]

Here is the 50pin edge connector definition:
https://files.edac.net/edac/content/series/og/English/EDAC%20345%20395%20Series%20Card%20Edge%20Connectors%20English%20Ordering%20Guide.pdf

And here a one for 34pin.
https://files.edac.net/edac/content/series/og/English/EDAC%20341%20391%20Series%20Card%20Edge%20Connectors%20English%20Ordering%20Guide.pdf

So 50pin edge connector is exactly 2.6inch or 66.04mm wide. As you probably will design in inches, and the connector is inch based format, it is probably better to directly use the inch values.

However the mounting holes for the screws are definately mm as well as the overall board.

[kanken6174]

Here are the measurements:

Of cause all on the backside, so you need to mirror it for frontside (or upside) calculations.

You cannot view this attachment.

Oh wow that's perfect, it fits exactly the wiki's measurements and isn't deformed in any way, thanks a ton it's exactly what i needed!
i didn't excpect someone to go out of their way to scan and measure everything themselves, thanks!

you guys should definitely  add this to the wiki.

[SerErris]

You may also find this handy :-)
https://www.cpcwiki.eu/imgs/8/87/464SchematicRedraw_white.pdf

[kanken6174]

You may also find this handy :-)
https://www.cpcwiki.eu/imgs/8/87/464SchematicRedraw_white.pdf

I had already found that one but thanks, it was really useful when pinning out that 20 (19) pin keyboard connector...