Amiga 600 schematics nearly put into Kicad

[Fackamato]

Originally Posted by hooverphonique

Hi Stedy,


what do you mean by


?

Traces too close to each other?

[Mick]

Originally Posted by kipper2k

looks great Mick, when are you going to build it I notice below the rom there is a lot of empty space, i think that could be utilized for headers as long as it is low profile as the KB sits close. A lot of cpu signals can be taken from the rom and custom chips so routing does not necessarily need to come directly from the CPU itself (I have never used Kicad

I'm not very good at soldering beyond the basic, I will have to pay someone to do it for me who is great at it but I can't seem to find a source for the A600 keyboard controller anywhere, would like to buy NOS if possible. I don't know if he'd want to be a beta tester either. I was hoping someone with soldering and diagnostic skill might have a go maybe they have a board with capacitor leakage or something. It all looks connected right to me and I'm working with Stedy to find any issues, the main concern I have is physical fit.

Originally Posted by Heywood

The number of vias in your board sound like a lot on the surface - just needing to control-shift-v and then pressing E to associate the VIA with a net that many times must have been draining. however when you consider the ratio of surface mount components to through hole, it is completely understandable you needed it (and I'm sure you were working to reduce how many you put there)

I only really routed the power, the majority of routing (signals) was done by FreeRouting. I don't even know if the power needed routing like I did (copying the original basically) maybe you can have a power plane but I didn't know how it would affect decoupling. I thought I might need to move some capacitors closer to IC's(?) and I wanted to keep it mostly original. According to amigapcb the original A600 board has around 4000 VIA's.

[Mick]

Originally Posted by Stedy

@kipper2K & mick
You do realise there's very little skyline where the RAM expansion fits, <10mm at the end?

There are many ways you could soup up the design, from easy to hard:
1) Mix L/R audio by 30%, using 4 resistors to make the audio less harsh.
2) Add some simple TTL logic to switch SEL0/SEL1 + MTR to allow DF0:/DF1: to be swapped for Gotek drives. Based on A4000 schematics.
3) Remove the RCA composite video connector and fit a 4 pin mini-din for S-video from the CXA1145/CXA2075 encoder. Connect Y to C via 100pF if you need composhite.
4) Remove the 23 way video connector, fit a HD15 VGA socket and a 4 pin mini-DIN (if you don't do option 3) in the space. Could also add the SCART/VESA VSIS fixes to the Amiga Sync signals to allow easier connection to video scalers/TVs.
5) Remove the RF modulator and the 5 pin square DIN plug. Fit a 2.5mm DC power plug and add a 12V to 5V converter and a -12V inverter. This provides a high current power supply for the unit by freeing up some space.
6) Fix the Amigas incompatibility with Type 1 compact flash cards on IDE by adding 74HC series TTL devices to correctly shift the IDE/CF signals to 5V CMOS levels.
7) Add the extra 1MB of chip RAM to the design by growing the PCB into the expansion slot. Maybe add a 8MB add-on?
8) Add a CPU connector slot.

It's easy to type this, to design, build and test takes time.

You should definitely do a modified version. I wouldn't know where to start with most of those for me it's just like a game of dot to dot.

[Stedy]

Originally Posted by hooverphonique

Hi Stedy,


what do you mean by:

tightly coupled traces

?

The spacing between tracks is close. With 1980s/1990s technology, to a large extent this is ok. Newer technologies from around 2000 onward this would cause issues as the signals are faster, this increases a phenomenon called cross talk, whereby adjacent, closely spaced signals interfere with each other. Adding power planes helps as it provides better impedance controls and changes the coupling mechanism slightly.

I consulted 'the book' (Art of Electronics 2nd edition from 1989) for PCB design, they talk about advanced layouts on 8mil/thou traces and 8 mil/thou spacing being mainstream technology. Modern PCB designs can use 4 thou/0.1mm trace width and separation, if the PCB technology and device technologies allow.

I'm glossing over a lot of PCB design stuff here, I left the other good book, no not the bible, High speed digital design at work. This details the complexities in more detail.

One issue, that affects these old systems is when you add new expansions, with newer, faster, more power hungry electronics. They show up weaknesses in the existing design. These weaknesses were not really present when designed in 1992, they met the requirements of the day. For a modern design, the approach used would not be suitable.

I've been doing PCB designs for over 20 years, learnt a few things.

[Mick]

Stedy how is your PCB only 188mm deep? I've had the ruler out on my empty case and it's around 188mm just from the back of the case to the front screw mount, then you have the 5mm at the front of the screw which is overall ~193mm?

[Stedy]

Originally Posted by Mick

Stedy how is your PCB only 188mm deep? I've had the ruler out on my empty case and it's around 188mm just from the back of the case to the front screw mount, then you have the 5mm at the front of the screw which is overall ~193mm?

Don't know, I checked the measurements 3 times. I measured a Rev 2D motherboard. In the zone is a PDF file which contains the measurements of my PCB, can some another A600 owner measure their PCB and compare against my measurement?

[Mick]

Does it only have half a hole at front centre (MT5) like this? explains a lot if so.

https://www.bigbookofamigahardware.c...mb_rev2d_1.jpg

I think I need to compare with an earlier board. Was that Commodore cost cutting or what? 5mm less PCB.. every little bit counts lol.

[kipper2k]

Originally Posted by Mick

I'm not very good at soldering beyond the basic, I will have to pay someone to do it for me who is great at it but I can't seem to find a source for the A600 keyboard controller anywhere, would like to buy NOS if possible.

Hi Mick,

I have created some designs for the A600 keyboard. An MX type which i intend to have it capable to be connected to a PC/Pi etc. It will allow you to connect to either the a600 motherboard connector or the MPU (U13)

I have also completed and tested a straight forward complete keyboard and plate replacement that will use cherry MX keycaps and connect to the regular A600 motherboard connector. I will show it off probably next week. Keycaps will be the original Amiga keycaps. More info on that later.

[Mick]

Hi kipper, it's U13 that is in critically short supply someone needs to replace it with something else going forward I think. Or is that what you're saying? someone could add another kind of interface to the board that's compatible with your keyboard and doesn't need U13? that would be great but I doubt I could. I could copy their schematics and layout though.

I will probably upload the full files tomorrow as I think I have gone as far as I can without access to a physical board. Stedy can upload what he has done when he has finished and maybe make a note of changes here? I mean the hope was anyone who builds on this work would share it here and elsewhere. I've wasted 4 weeks if people just let it die.

I'm quite proud I got this far. I'd never even used KiCad a few months ago.



p.s. if anyone is wondering net U12_1 is ground and U13_1 is VCC for some reason, I asked why earlier in the thread but nobody could answer.

[kipper2k]

U13 could be replaced by something similar to the PIC chip that we are using for the MX. I will ask Mike if he is willing to produce something for the a600, it may need the footprint to be changed. It all depends on the interest level shown by people if they want to buy/build/further develop this board

[Clamshell]

Very cool, you can be proud of that!

[Mick]

I've uploaded my progress to date into the zone, maybe Stedy or someone can host the files or they'll disappear after 60 days?

If anyone is looking to finish it I think it's basically a case of checking PCB dimensions, connector locations, hole diameters and pad sizes. Also, checking schematics in case of any mistakes but that is what Stedy is already kindly doing. The whole layout is accurate to what AmigaPCB says for a Rev 2A PCB (and using datasheets for footprints) rather than any physical board. Any skilled board designers can probably route it much better as well.

If anyone has the overall length and width for an A1200 rev 1.x I was going to give it a try since about half of the A600 schematics can be recycled, in fact I've already drawn them up and got all footprints ready.

[Stedy]

Hi,

I'll upload the project files to Github soon, let me finish the schematic checks and prettying I've nearly fixed the renaming of the Vcc/Gnd nets to U13_1 and U12_1, page by page I'm getting there.

What name for this project?
A600+? (when a few tweaks are added)
A600_2019?

@Kipper2K

Would be interested to see what you come up with regard to the keyboard MPU. Was cleaning my water damaged A500 today and saw a MOS technologies MPU in the keyboard, I bet they used a similar 650x microcontroller for the Keyboards of other units.

@Mick,
Have you seen the ReAmiga A1200?
http://eab.abime.net/showthread.php?t=93836

Admittedly, it's mainly the PCB files.

My A1200 is in pieces at the moment, it was also water damaged slightly, it's drying out. A dehumidifer leaked over two of my four Amigas
Will look at measuring it in the near future, it's a rev 2B, the one with the small extender PCB for mouse/joystick.

[Mick]

Err I dunno, just call the files OpenA600 or something.

I've got a ReAmiga and Chucky's work is awesome I'm just kind of going in a different direction and maybe trying to get more people involved in development with this, there may be a lot more people in the community with electrical engineering know how (unlike me) who just don't have the time to do what I did but can easily build on it and come up with their own unique ideas that others wouldn't think of. I'm thinking of putting it into MATX later if I can, or maybe someone else will do it?

If you want just upload your modified files separately and put your name on them, keeping mine original. It's that sort of evolution I hope to see.

[AJCopland]

Put the project on GitHub or something, that's what those site are for, hosting and sharing projects like this. For free.

EDIT: and immediately after posting that I see that's exactly what Stedy will do!

[Mick]

Stedy, I forgot to say I made a few changes since sending you the files but you might just be able to replace the .sch files and copy the libraries over. I dunno.

[Mick]

How did you fix the VCC/GND nets Stedy? I'm seeing the same thing again just on different nets.

Also, does anyone know is the reason why A1200 didn't have a RTC because Commodore made a mistake? it seems like they thought the RF5C01A was a 20 pin rather than 18? unless I'm missing something?

[Mick]

Once this is done I'm going into retirement.

[xyzzy1]

How far do the power and ground planes protrude in to the edge connector?

[Stedy]

Originally Posted by Mick

How did you fix the VCC/GND nets Stedy? I'm seeing the same thing again just on different nets.

Also, does anyone know is the reason why A1200 didn't have a RTC because Commodore made a mistake? it seems like they thought the RF5C01A was a 20 pin rather than 18? unless I'm missing something?

Hi,

I'm slowly fixing the VCC/GND nets by deleting all global symbols that connect to VCC/GND and connecting all devices to VCC/GND symbols. A global symbol overrides a local net name.

I finished reviewing the schematics of the A600 reborn (it's name for Github) last night. Apart from the oscillator being disabled, it appears Ok. The schematics need the VCC/GND tidy up and a few symbols need tidying up, especially the IDR/expansion connectors. Working on this slowly, then I'll upload the design to Github. Will also check some critical signals in the layout first. Schematics then PCB

The RTC was removed to save cost. The A1200 rev 2 were shrunk to save PCB costs, $1-$2 per unit over a few million, adds up! There is a compatible alternative to the RFC501, the Epson RTC-72423 should work.