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avatar_SerErris

464 Schematic redrawn

Started by SerErris, 16:57, 03 November 23

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SerErris

Hi,

I always found the available schematics from the Service Manual pretty bad quality. It is an A3 sheet and therefore the font is pretty small. And that also means that some pixels blend into each other. 

So I took the time to redraw the Schematic with some improvements for readability
  •  I added a GND symbol where they put in a 0
  • corrected the MUX connections showing a negated imput (that is actually supposed to be a 0)
  • Added the Barrel Connector and korrected the CP001 connectivity (no there is no GND on Pin A) and Pin C is connected to the barrel connector.
  • Named the clock signal CLK (PHI).
  • Changed the pullup on XTAL input of GateArray to pointing up.

I now would love for someone to doublecheck my output to validate if that is correct and I did not make any mistakes.

As I wanted it to be stylisch (historic) I used the DIN Normschrift for any technical drawing as it has been used in Germany over the last centuries. The benefit, the font is very clear and good to read. 

The overall benefit of the new drawing is: It scales to whatever you want it to scale. So if you want to print an A0 version as a wallpaper - you can do this without any quality loss.


Please let me know any misstakes and I will correct them ASAP.

I can also release the original .svg image from Inkscape if anyone is interested in working with it.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

d_kef

#1
Thanks for the excellent work!
Now my reading glasses are enough to make out the schematics. No need for a magnifying glass anymore  :D :D :D
After a first quick look i found out that the label and value of the luminance driver transistor Q102, in the video out section,  is missing.
Thanks again.

d_kef

SerErris

Great, good catch. Added it.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

Bryce

If you went to all that trouble, why didn't you do it in Eagle or KiCad so that the board could be created too?

Bryce.

SerErris

#4
Because I wanted to retrace the original lines. in the original drawing.

But I think you are right, I will do this next :-) Just another topic for the long evenings.

In Kicad I need to redraw all the chips to make them look similar, as they will have their connections in all different places (typically where the real PINs are) and you would paint Busses instead of single lines. It is much harder to recreate the original drawing in Kicad. You could put up a completely new drawing in Kicad without bigger issues, but this exact one is a real challenge.

Also what I like about the old schematic is that they make smart simplifications. For instance the RAM section. That is something you simply cannot do in Kicad. You cannot draw a single 8in1 RAM chip and then all connections work correctly afterwards.

So a Kicad Drawing will be different, and that was not the goal of this drawing.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

pelrun

I've already done the hard work for the 6128. Modifying it for the 464 is mostly just removing things from it, then redrawing the board.

You absolutely *don't* want to try and duplicate the structure of the original schematic in an ECAD tool. It makes many design choices that are sensible for a hand-drawn schematic and absolutely terrible for a proper CAD layout - half the reason I had to reverse engineer my 6128 from scratch is because the official schematics *weren't* great.

SerErris

I am half way through in KiCad. And yes, you want to have proper connections for everything, so I do use Busses and other proper Power lines, that are currently not really incorporated in the Schematics. Some chips do not even have power connections drawn at all, for instance the Printer Latch. 

Also the Tape Port is not drawn correctly and the Power Input via the Barrel Connector is not in the schematic at all. 

Anyhow, I will finish it this weekend for the 464 in the first draft in KiCad. However I am not sure who will actually work with it and recreate a Mainboard :-D

I can only imagine how small this could be if you would go all small SMD and 4 Layer board. You can even put on all modern components now and the largest chips will be the AY3 and the GateArray - even if we redo them as reincarnations...  Also the 8255 PIO .. not sure if that is even available as a SMD small footprint version.

So for what it is worth ... 

Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

SerErris

#7
Update the schematic to Version 1.0 now.

1. Incorporated correction from @d_kef
2. Fixed a wrong PIN Number on IC125, I had two time Pin 3.
3. Corrected non aligned PIN Numbering on IC114
4. Added missing connecting points on pull-ups in Reset Circuit
5. Added missing connecting points on OS Links GND connection
6. Added missing connecting points on pull-downs in Sound Circuit
7. Non visible - cleanup of original .SVG to better support different ColorSchemes.

You cannot view this attachment.


@d_kef can you please walk through the whole document chip by chip and double check any connection and number etc. ?

That would be fantastic to have a second pair of eyes on it to clean as many errors as possible from it.

Thanks
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

SerErris

Okay, gone over it again and found some bad alingments but also some wrong Pins and names.

1. Corrected resistor between pin7 IC104 and Pin 10 RAM to R146
2. Corrected connection bubble on pin1 of IC105
3. Corrected DISPEN pin on GateArray (Pin23)
4. Added expansion connector pin numbers to the signals coming directly from it.

So now, please find Version 1.01 attached.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

d_kef

Quote from: SerErris on 18:27, 04 November 23d_kef can you please walk through the whole document chip by chip and double check any connection and number etc. ?

That would be fantastic to have a second pair of eyes on it to clean as many errors as possible from it.
I took a more thorough look at v1.01 during my morning coffee time.
The capacitor labeled C120 (at the 16MHz generation section, between pin 3 and 4 of the 7400) should be C129. C120 is the decoupling capacitor of the CRTC.
Also a remark. /BUSAK, /NMI, /HALT, /RFSH are only connected to the expansion port, so maybe you should also add the expansion connector pin number to those signals.

d_kef 

SerErris

Thanks alot @d_kef really appreciate the time you are putting in.

I changed C120 and also added the bus connctor pin numbers to the signals you mentioned. While doing that I also found out that I used the wrong font size for those signals. It is supposed to be all 6pt and it was 5pt.

After looking at it I do think this is best printed at A1 size. Then you can easily read everything.

If you print it on A2 it will be better to handle on the table, and still readable. A3 is very small as the original was very small on A3. So I do think that the real original was never A3 but must have been larger.

Find 1.02 attached. Will upload now also to the normal WIKI.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

Urusergi

#11
Thank you very much for this wonder 8)

If there are future updates, could be centered "IC101",  "IC110", "IC112", "IC125", "Q101", "Q102" and "Q103" please?

Ir seems that IC105 printer port latch is IC106?

Saludos.

SerErris

Thank you @Urusergi,

You could argue about aesthetics I think, however I centered them all now.

But how I could miss that this is wrong IC (printer latch) is beyond my horizon.

:picard:

I will wait for further responses a day or two before releasing the next version.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

SerErris

Just for convenience and quick view, I post a png version here. But that has the same problem it is not scalable and even it is huge, (10Kx7K), it still suffers from blurring. However that is only visible at 100% and you would potentially never view it at 100%,.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

Urusergi

There is a black dot on IC110, pin one (reset circuit). Also, there is a triangle in the ground symbol (sound mixer).

It's a work of art, congratulations, I would like to learn to use Inkscape ???

Saludos.

SerErris

Thank you for continued checking.

Removing the dot.
Also the triangle is just a filled line, which obviously should not be filled.

Inkscape is not that complicated to use. And it is very powerfull for this kind of work. 

You actually put the original document in the background layer and then start drawing on top of it in multiple layers. 

I do have layers for chips, R C D, connections, the arrows, that are in the middle of the schematic and text.

Then a lot of stuff is grouped to find things easier.

I will share the svg later on, you can have a look to it and use it as a starting point. I am always learn new tools by doing something that I do have interest in.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

Urusergi

#16
Quote from: SerErris on 19:56, 06 November 23Inkscape is not that complicated to use. And it is very powerfull for this kind of work.

You actually put the original document in the background layer and then start drawing on top of it in multiple layers.

I do have layers for chips, R C D, connections, the arrows, that are in the middle of the schematic and text.

Then a lot of stuff is grouped to find things easier.

I will share the svg later on, you can have a look to it and use it as a starting point. I am always learn new tools by doing something that I do have interest in.

Thanks, I just installed the program 8), now I need a tutorial because I'm not able to do anything :picard:

The nodes of R101 & D101 and R109 & R110 should look more like the nodes of R138 & R139, don't you think? They would look better in my opinion.

On pin 11 of the Z80 it would be better to put +5V

Saludos.

SerErris

You mean the connection to the +5V rail?

So like this?

You cannot view this attachment.

I also cleaned up R102 to connect to the same rail. 

I am not sure which one is better.

On the one hand this version looks cleaner.

On the other hand, the version before is technically correct, as the dots indicate a connection. However if we consider the +5V to be a rail, then all the lines conect to the rail and I also think it is clear and it is what they have done on the other parts, for instance on R103-R108.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

pelrun

There's no need for a dot on a 3-way intersection, as the connection is unambiguous. Some designers deliberately only ever use 3-way connections, that way it doesn't matter if a dot is accidentally left out - when 2 crossed wires need to connect, you just stagger one wire to get 2 3-way connections instead.

Style isn't just about what "looks good", it's also about what sort of errors you can avoid.

Urusergi

#19
Quote from: SerErris on 10:34, 07 November 23You mean the connection to the +5V rail?

Yes, the +5V rail may be fine when there are many connections but in this case I think  it's better in this way, like in R138 & R139.

SerErris

I see, yes I like that better as well.

You cannot view this attachment.
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

Urusergi

Quote from: pelrun on 12:10, 07 November 23There's no need for a dot on a 3-way intersection, as the connection is unambiguous. Some designers deliberately only ever use 3-way connections, that way it doesn't matter if a dot is accidentally left out - when 2 crossed wires need to connect, you just stagger one wire to get 2 3-way connections instead.

Style isn't just about what "looks good", it's also about what sort of errors you can avoid.

You're right, but in this case @SerErris is tracing an already created scheme, and he wants it to be as close to the original as possible with slight improvements.

Un saludo.

SerErris

So,

as it looks like we now found all the errors, please find the latest version of it (1.04).
Proud owner of 2 Schneider CPC 464, 1 Schneider CPC 6128, GT65 and lots of books
Still learning all the details on how things work.

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