1088XEL Alternative Mother-Board Project

[+MrFish]

Yes I agree that the toggle isn't the sexiest looking mouse select switch option, but it was the least expensive, and as you said re-purposes holes that were already there. Another option would be to add it to the top panel in the form of a rocker switch, having the associated LEDs to either side of it. But this also gets a bit trickier with the Mouse Switch PCB, since the switch would need to mounted first to the panel (pressed in) and then soldered to the PCB underneath. I suppose this is all doable, and perhaps I'll look into it if and when I make another top panel. but for now it is what it is.

 

However with all that said, the toggle from an ergonomic standpoint actually makes more sense and is very easy to operate, and it also gives better visual feedback as to what position it is in.

 

I'm just nitpicking; don't worry about it.

[Dropcheck]

 

No problem, it was a good exercise in specifying some stuff that needs to be nailed down anyway

 

As for the 'alternative' to the SIO connector which is actually a DA15M (see note below), it is the shorter .318" variety (Jameco P/N: 71125) .

I think these guys are becoming less common, since I wasn't successful at locating this at either Digi-Key or Mouser, unlike the high density triple row type used for VGA.

 

However just to make this public knowledge, we got a generous donation of 50 real honest to goodness NOS SIO PCB Jacks, with a possibility of more to come from that same source. And I also know of one other source that has 100+ that could probably be persuaded to part with some of those as well. So we're sitting pretty for MacRorie's first XEL run, and won't need to substitute the DA15M.

 

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I know everybody calls these things DB no matter how many pins it has, but this is officially a DA series due to having 15 pins.

Quote from Wikipedia (https://en.wikipedia.org/wiki/D-subminiature)...
"Each shell size usually (see below for exceptions) corresponds to a certain number of pins or sockets: A with 15, B with 25, C with 37, D with 50, and E with 9." 

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- Michael

 

Yikes, on backorder until 9/27/2017! But at least the price is right.

[+mytek]

 

Yikes, on backorder until 9/27/2017! But at least the price is right.

 

Hopefully you won't need it if the supply of real SIO connectors holds out .

 

- Michael

[+mytek]

I hate to say it, but another problem was found with the design. But the good thing is that it was super simple to fix and is done

 

It was a pull-up problem on the Color-Out line of GTIA (pin 21). The original pull-up which which is 1K to +5V from pin 21, was not sufficient and in some cases aberrations would randomly appear on the right edge of the screen. On my system I rarely ever saw this symptom, and it only existed for a second or two after powering up, so I dismissed it as normal warm-up jitters. But when I was doing some more testing on Simon's board, his was quite pronounced, and sometimes didn't go away until I brought my hand over near the GTIA. That's when I began to suspect that some part of the video signal was on the verge of floating. So out came the ohmmeter, but everything appeared to be ok . I then started to draw the conclusion that the 1K pull-up resistor was just not enough for at least one of the signals. Suspecting the Color-Out, I used a screwdriver and touched it when the aberration was present. This caused it to immediately disappear. After pulling the screwdriver away, the 'noise' returned. So I grabbed a couple different value resistors and started paralleling them across the one in the resistor array (RN8) that was responsible for pulling up pin 21. After a few trials I zeroed in on using 1K across the original 1K in the array. Since the luma lines looked solid, I decided to not change out the array for one with a lower value, and instead opted for just using a parallel resistor across only the one resistor pulling up pin 21.

 

So why did I need to do this? I think it has a lot to do with the fact that the Color-Out passes through an analog switch (74HCT4053) as part of the VGATE video switching circuit, whereas the luma lines all pass through a separate Quad AND Gate (74HCT08). Most likely the analog switch presents a much higher impedance to the Color-Out line of the GTIA, than the original Atari circuit. So what worked for a pull-up on the original A8, was just a bit too weak when no longer driving into the simple transistor amplifier circuit, which likely biased it towards the +5V rail. No matter the reason, it now appears very stable on all 3 systems I am testing at my shop (Stephen's, Simon's, and mine) after adding the additional 1K pull-up resistor.

 

The schematic and layout has been modified and updated on my website. The added resistor is ID'ed as R51 (Area 51 ).

 

This board reminds me of a child who doesn't wish to leave the nest when growing into adulthood, all the time kicking and screaming to remain in it's parent's home.

 

- Michael

[+Stephen]

It's almost a wonder these old bucket of bolts (the original Ataris) ever flew at all! Talk about being on the edge of "barely working".

[Bryan]

I sent a PM about the color issue.

[+mytek]

Bryan and I are working on an even better idea. Not something complicated or that will impact the schedule, just a slightly different approach to resolve the floating color issue. If it goes as planned, everything that is needed is already present, and it just needs a little tweaking to make it right. Should have this worked out tomorrow.

 

- Michael

[Matej]

Beautiful enclosure!!! I going to post it on fb group at evening.I was on holidays...

[+mytek]

Fixed the Color floating problem the correct way thanks to Bryan. So here's the deal... the real problem was the open input (pin 5) on the 74HCT4053 analog switch. So whenever the video signal was gated OFF the open input of the switch got routed to the UAV's color input pin. So with the right opportunity noise could get into the color input and start producing weird color aberrations in what should have been the blanked out areas of the screen. Now I really should have known better than to leave this input floating, since this is one of the first things you are taught not to do when learning about electronics. And in my defense, I had previously tried to tie this unused input to ground, but that just produced a line in the over scan area. Little did I know that +5V represented a no-color situation, not ground (inverted logic). So by connecting that unused input to +5V, we now have the correct behavior with nothing appearing in the gated OFF areas of the screen.

 

this fix was very easy to implement in the PCB layout, only required specifying a connection to one of the inner power planes. So we are back on track

 

 

Note: My website has the updated files reflecting these latest changes.

 

- Michael

[+mytek]

Correct me if this has been discussed already (haven't been following too closely as of late), have you explored any other options for the toggle switch on the side?

It looks alright, but I think something more modern or low-profile would fit in better with the rest of the design (perhaps a rocker or slide switch).

 

Hey check these out...

I got these on order, and thought this might help blend the toggle switch in better with the black case. Should be interesting to see what it looks like.

 

- Michael

[+MrFish]

Hey check these out...

 

I got these on order, and thought this might help blend the toggle switch in better with the black case. Should be interesting to see what it looks like.

 

They also make these cool illuminated switches.

 

I guess the LED openings you're using are already in the case, though.

 

Also, these are $6.50 a pop.

 

 

[+MrFish]

There's also this plain black one.

 

Edited August 19, 2017 by MrFish

[+mytek]

 

They also make these cool illuminated switches.

 

I guess the LED openings you're using are already in the case, though.

 

Also, these are $6.50 a pop.

 

G12JPCF, G13JPCF.jpg

 

 

This illuminated one looks real cool . Do you have a link to it? I was also wondering if it had a dual color LED?

 

Presently I am using the two screw holes in the case for the LED indicators, and the the switch nut to hold the PCB assembly in place. However with the switch you suggested, it has no mounting other than the PCB connections, so I would need those screw holes for mounting the switch PCB instead. Hence the interest in having a bi-color LED built into the switch itself .

 

BTW, I picked up 20 of those switch covers for just under $3 with free shipping. Ultra cheap .

 

- Michael

[+MrFish]

This illuminated one looks real cool . Do you have a link to it? I was also wondering if it had a dual color LED?

 

Presently I am using the two screw holes in the case for the LED indicators, and the the switch nut to hold the PCB assembly in place. However with the switch you suggested, it has no mounting other than the PCB connections, so I would need those screw holes for mounting the switch PCB instead. Hence the interest in having a bi-color LED built into the switch itself .

 

For the On-Off-On switch it uses red for one "on" position and green for the other "on" position. So, yes, dual color.

 

You may be able to find it cheaper. This is just the first place that came up:

 

[Edit: I had linked you to the On-On switch -- hence $6.20 price. Here's the correct one.]

Digikey: NKK Illuminated Toggle Switch

Edited August 19, 2017 by MrFish

[+mytek]

 

For the On-Off-On switch it uses red for one "on" position and green for the other "on" position. So, yes, dual color.

 

You may be able to find it cheaper. This is just the first place that came up:

 

Digikey: NKK Illuminated Toggle Switch

 

Actually $6.20 a piece. I must have been looking at another one that was $6.50

 

Picked up the datasheet on that. I love it! Yes it would be nice if it were a bit cheaper, but this project overall is not inexpensive, so paying a bit more for the extra coolness factor doesn't bother me all that much. In fact for my own personal use I'm looking at building 3 complete systems, one for each place I hang out. They will become my go to A8's, and I'll likely be storing away all of my original systems, or just have them on a shelf for display.

 

However I will do some looking around for other sources for this or a similar switch with a hopefully lower price tag.

 

Thanks a bunch for the suggestion and the link

 

- Michael

[+MrFish]

Newark is the cheapest at $6.42 according to this: Price Comparison

 

[Edit] Mouser isn't on the list, but I checked them too and they were at $6.98.

Edited August 19, 2017 by MrFish

[+MrFish]

Just a note, though, Newark is cheaper for a single one, but Digikey is cheaper when you move up to the 10 piece break. So if you plan to buy together with some other people you can save some.

[BillC]

 

This illuminated one looks real cool . Do you have a link to it? I was also wondering if it had a dual color LED?

 

Presently I am using the two screw holes in the case for the LED indicators, and the the switch nut to hold the PCB assembly in place. However with the switch you suggested, it has no mounting other than the PCB connections, so I would need those screw holes for mounting the switch PCB instead. Hence the interest in having a bi-color LED built into the switch itself .

 

BTW, I picked up 20 of those switch covers for just under $3 with free shipping. Ultra cheap .

 

- Michael

Digikey does carry the bi-color(red/green) version of this switch, the link has the different types.

 

https://www.digikey.com/products/en/switches/toggle-switches/201?k=&pkeyword=&pv522=42&FV=fffc0168%2C2080002%2Cffe000c9%2Cffec089c&mnonly=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

[+MrFish]

Digikey does carry the bi-color(red/green) version of this switch, the link has the different types.

 

https://www.digikey.com/products/en/switches/toggle-switches/201?k=&pkeyword=&pv522=42&FV=fffc0168%2C2080002%2Cffe000c9%2Cffec089c&mnonly=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

 

I already linked to the dual color ones you're pointing to here. All this shows in addition is just ones for other mounting angles.

Edited August 19, 2017 by MrFish

[santosp]

Looking on this project from time to time, I am asked how much it would cost completed in a case, with all the bell and whistles -till now- for the potential builder?

[+orpheuswaking]

Depends what case you use and what options you use. At a minimum you need a fully populated board, a UAV, and a u1MB... then you have the option of a VBXE or Sophia. You can also add the XEL-CF and dropchecks cart slot extender.

 

That's before you add the case. We also don't know if anyone is going to sell complete asembled boards or just a group buy/kit

 

So the answer is, it depends lol

[Dropcheck]

Don't forget the SDriveXEL (similar to the XEL-CF option) and the XF551XEL basic board with an XF551 compatible 3 1/2" or 5 1/4" drive if you want real pedal to the metal floppy experience and you are using a MicroATX or MiniITX case with a free 3 1/2" and 5 1/4" drive bays.

[AtariNerd]

* Speaking of which, just received a package with some of said goodies, yesterday.

[Gandor]

Looking on this project from time to time, I am asked how much it would cost completed in a case, with all the bell and whistles -till now- for the potential builder?

Are you going to build some?

I would be interested in one

[santosp]

Are you going to build some?

I would be interested in one

 

No I was just curious for the total cost! But as the other guys said above, have to do with what you want to add on this.

Speaking on this, if none arrange a group buy construction and you can gather all the needed parts, I can do an exception. I think you know my postal address....