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bakersnarkMDW
BSS wrote:
No extra storage. I twisted and picked at the yellow cap for a while and nothing happened. I've had this screwdriver for about 15 years. You'd hope I figured out something like that by now.


It was an obviously unsuccessful ‘educated’ guess. As I couldn’t see the handle I could only go by the bit I could see, and the bit-holding section around the metal shaft seems molded slightly differently from mine so I assumed it was the other version I knew of with the hollow handle, but they obviously had other iterations. It may be yours is older than mine, which may have been acquired as recently as within the last decade!
As I suggested above, I don’t mind the solid handle as it has a better feel - convenient though the extra bits might be, it gets annoying having them rattling in the handle. Besides, with a screwdriver that size I find I’m usually just using a few standard bits, and they can be easily stored in the part visible in your photo.
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BSS
The discussion in the other thread had me thinking about ways to hack around doing a custom PCB.

So here's the already designed Pixels Past board at Osh Park. Can just press the order button and get a few of these:
https://oshpark.com/shared_projects/fqTcNFkn
[e351599d5fbe367e02d567bd51042912] 
So I think it would be possible to put a 24 pin socket in this board, then stick my 28 pin chip in there with the ends hanging off. Then install bodge wires onto the loose pins. Preferably I would stack two sockets on top of each other so I don't need to do nasty things to my EEPROM, but I don't think the cartridge housing is fat enough to fit all that.

At the same time I made some progress on the Eagle project. The biggest problem I had up until this point was that there's no built-in edge connector component. Don't know why, because there's thousands of different versions of every other component you can imagine. Also there's tons of downloadable libraries for things that don't come with Eagle, but of course no edge connector ones I can find. Making your own library is possible. They're just XML definitions. It's just a pain I didn't want to go through.

I came across someone else who had made a bank switching cartridge that uses a 32K EPROM and DIP switches to select the game. This was also made in Eagle. So I open up the project to see what they did, and stumbled across an export function for the components. I export his edge connector and import into mine. Suddenly I have something workable.

This is my schematic: schematic.png 
And this is my layout so far:
boardlayout.png 
I haven't done any of the traces yet. That comes next. Right away it looks like the resistors are gigantic. Maybe I should switch to SMD ones? Actually I'm not sure I need them at all. It just felt like the safe way to go.
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bakersnarkMDW
BSS wrote:
...
So I think it would be possible to put a 24 pin socket in this board, then stick my 28 pin chip in there with the ends hanging off. Then install bodge wires onto the loose pins. Preferably I would stack two sockets on top of each other so I don't need to do nasty things to my EEPROM, but I don't think the cartridge housing is fat enough to fit all that.


So do most of the pin placements on the 24 pin EPROM match the 28 pin EEPROM? Are there just a couple of extras at one or both ends?  It might be feasible to drill a few extra holes in the board to accomodate a 28 pin socket, though it looks a little tight around a couple of the traces.

BSS wrote:

...
Right away it looks like the resistors are gigantic. Maybe I should switch to SMD ones? Actually I'm not sure I need them at all. It just felt like the safe way to go.


Not sure what wattage resistors have been drawn (& what wattage is required) but I would guess half a watt would be fine. Shouldn’t need to muck around with surface mount.

21553DF3-8078-4BDA-9DA1-E89D0F4D1FAD.jpeg

That's a 10kΩ half watt metal film resistor next to a 7410 (same package as a 7404).
Even that 0.1μF capacitor looks pretty massive on the board layout.
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BSS
OK I just submitted my board design to Osh Park. Should take a couple of weeks to arrive.

oshpark.png 

Ended up using the spare inverter pins instead of pullup and pulldown resistors. Still not sure if it's necessary. I just don't know how much power the Atari puts out, and how these chips react to that on their logic lines.

Surprisingly I got the routing done with no vias. The Pixels Past one has a few, and even the original Boxing board has 13. Surely I've done something wrong.
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bakersnarkMDW
BSS wrote:
...
Surprisingly I got the routing done with no vias. The Pixels Past one has a few, and even the original Boxing board has 13. Surely I've done something wrong.


That’s the spirit - must be an error! 😉

What’s the back of that Boxing board look like? Seems they’ve run all the traces from the chip legs on the component side of the board then shunted the ones going to the edge connector on the solder side through some distance from the chip. Could there have been a manufacturing limitation at the time that made it safer to not have tracks running from the pads having solder applied to them (may have been some small chance of trace damage). 
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BSS
The Osh Park constraints allow for much smaller traces than I used.

Anyway it looks like they did a flood fill and connected one of the ground pins to the shield. Some EMI nonsense, no doubt.
MVIMG_20180330_230928.jpg 
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bakersnarkMDW
The US FCC was on a bit of a power trip on regulating EMI/RFI at that time. Atari ran foul of it with their 8-bits the 400/800s - to build in an RF TV connection at the time required a hefty cast-aluminium shielding chasis to be included which added a fair whack to construction costs and hurt their sales a bit (probably why we didn’t see so many in Australia). Their competition at the time (TRS-80, AppleII, Commodore PET) all just had a video out for a monitor and any RF connection was done via an adaptor box seperate from the computer itself. Even when the FCC split devices into class A and class B, they instituted an onerous testing regime which required some additional legal gymnastics to avoid crippling expense. It all got ironed out just in time for the launch of the C64!
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BSS
Lots of progress has been made recently.

First, the boards arrived:
IMG_20180418_174302.jpg 
Special thanks goes to Department of Agriculture for ensuring I wasn't importing animal or foodstuffs. I know PCB looks similar under x-ray.

The first thing I did was compare it to the empty cartridge housing. Problem number 1: they don't fit.
MVIMG_20180418_174740.jpg 
The height is probably correct, but it's too wide. The smaller part doesn't fit between the plastic guide, and the larger part doesn't fit between the screws. There's only a couple of millimetres in it. Small enough to be filed back, but because I placed all of the parts so close to the edge, I'd be cutting through traces to do it. So that's at least two changes for the next revision.

Whatever, the board still fits in the Atari's socket by itself, so I press on...

First thing I did was solder in a 28 pin socket for the EEPROM. Then flip the board over to add the inverter chip.
MVIMG_20180420_183553.jpg 
Good luck soldering that. Also desoldering a 28 pin DIP has a difficulty of somewhere between hard and impossible.
uh.png 
It's also the only socket I have, so I quit for now. I'll have to buy more this weekend.
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bakersnarkMDW
Get yourself some machine pin socket strips. I have some. 
82F6F267-BC34-4341-BBF7-E3A2D8070AC3.jpeg
Snap to length and put them on the top and bottom DIL solder pad rows. Good quality, don’t need a matching socket sized to each chip and it leaves the board underneath exposed in case you forgot to do something! 😉  

https://www.jaycar.com.au/machined-pin-ic-socket-strips-32-way/p/PI6470

(& don’t forget to check those boards for fruit fly [the first earthlings in space!] 😀)
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BSS
Ta. I'll try those strips instead.

I also just noticed that the board is inside out. So I can't use these at all.
IMG_20180421_162527.jpg 
Comparing to Boxing, on this side the rightmost pin is a ground, and the next is +5v. They're the thicker traces. On my board they're on the left.

I guess I had better get working on the next revision.
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bakersnarkMDW
Can’t claim I’m following the board architecture precisely but most traces seem to be a straight edge connector to chip leg matchup. Don’t know how symmetrical it all is but with solder pads on both sides of each hole I was wondering whether something could be done with a little creative trace cutting and jumpering combined with possibly flipping the board, rotating the chips and/or mounting both chips on the same side of the board?

Failing all that you should at least be able to wire one of the boards up to act as a connector to your console for a breadboard cartridge.
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BSS

OK I found that the edge connector was upside down. So the solution is to rotate it 180 degrees, then attach it to the bottom layer of the board. This way I could rewire everything exactly as it was, just on the opposite layer.
Also slimmed it down a bit and gave more space at the edges. I've submitted version 2 to Osh Park.

I guess I could try using the v1 boards as a breakout onto breadboard. But as revealed in the latest podcast, there's something else that has my attention now...

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bakersnarkMDW
BSS wrote:

OK I found that the edge connector was upside down. So the solution is to rotate it 180 degrees, then attach it to the bottom layer of the board. This way I could rewire everything exactly as it was, just on the opposite layer.
...



So does this allow any board flip/component rotation combo which would get the V1 board near enough to working for a couple of jumpers to make it go? (You have to cut a couple of traces to make it fit anyway 😛)

I could possibly spare a jumper or two to make it neat (& colourful). 😉

F57E8526-8E73-410F-9F14-EC1BFD5A4879.jpeg
T
hat’s about half of them! 😃
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BSS
That's a lot of jumpers!

The chip pinout isn't really symmetrical. Basically there's a few odd pins in the middle of the chip, and the upper end is mixed around a lot. This is probably another result of backwards compatibility with the smaller packages. So even though I've just flipped all the conductors for the v2 design, I think there's enough differences that I wouldn't bother with cutting and jumpering.
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Mar
What are the chances of - once PCB gate closes - that there’s going to be a boxed copy made? I’d be keen to add it to the collection. *Frytakemymoney.gif
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