1088XEL Atari ITX Motherboard DIY Builders Thread

[larryleffaovell]

11 minutes ago, DrVenkman said:

Do you have access to an oscilloscope? I’d check the waveform shape and stability of Phi2.

That's what tf_hh already recommended to me, but I've only a simple 200kHz oscilloscope, unfortunately. But assuming the signal is "bad", what can I do to fixup signals quality?

 

[+DrVenkman]

19 minutes ago, larryleffaovell said:

That's what tf_hh already recommended to me, but I've only a simple 200kHz oscilloscope, unfortunately. But assuming the signal is "bad", what can I do to fixup signals quality?

 

If you have a spare, swap the 74F08 (U11).

[larryleffaovell]

15 minutes ago, DrVenkman said:

If you have a spare, swap the 74F08 (U11).

Just received a new set of all 74's for upcoming projects, so I'll try and report...

EDIT: Nope, U11 swapped, but same result.

Edited May 4, 2020 by larryleffaovell

[rockdoc2010]

On 4/30/2020 at 1:32 PM, Mr Robot said:

It sounds like display compatibility issues to me. The Sophia DVI is tuned to a specific resolution that maybe your screens don't support, you might need to get a different firmware for it, check your displays' capabilities and which firmware you have installed.

 

The VBXE outputs 15Khz and most monitors nowadays can't handle that, get one of these https://www.amazon.com/s?k=GBS+8200 (don't forget the cables!) that will give you a 'regular' VGA display and allow you to verify that you are actually getting output from the VBXE.

 

 

Does anyone have a recommendation for the name/quality or functionality of any give board? It seems as thought there are many makers of said board. And is there a tutorial as to how to install the VBXE to the GBS?

 

Thank you 

Douglas

 

[+DrVenkman]

5 hours ago, rockdoc2010 said:

And is there a tutorial as to how to install the VBXE to the GBS?

The VBXE goes into the Atari.

 

The GBS has RGB input. So you’ll need a DIN13 to RGB RCA plug wired up. The VBXE output will go out the DIN13 and into the GBS via Red, Green and Blue RCA connectors.

[bfollowell]

OK, I've started troubleshooting a little again. Just fits and starts as I find a few minutes of time. To refresh, my system is hanging at boot. I get either a blank screen or it hangs at the 1088XEL logo. From there, if I press F12, the system will go ahead and boot. I know that "hang" isn't normal though. Once I press F12 and get it booted though, everything seems to work as I would expect it to.

 

So, remembering some of the suggestions, I've gone through everything from U7, the TK-II out. I've checked for any shorts or opens and can't find any and I've confirmed continuity from the shoulder of every pin on U7 out to the next component or junction. Same from the PS/2 keyboard din back the previous junction. I've confirmed the polarity is correct on D1 and C19 is a small ceramic and doesn't have any polarity. As near as I can tell, everything is spot on. I think the soldering looks decent and I've cleaned the solder joints with IPA. I've confirmed the TK-II configurations from the SDX menu and everything looks good there. I've confirmed my PIC is programmed with v2.4 of the firmware. I really don't think there is anything wrong with any of what I've checked so far.

 

I haven't had a PC with a PS/2 port in about a decade and I got rid of all of my old PS/2 keyboards years ago. The only one that I currently have is the one I ordered just for my XEL. I'm using a Logitech Y-SU61. From all I can tell, it appears to be just a run-of-the-mill PS/2 keyboard and I've used nothing but Logitech in almost twenty years. I hate to, but I wouldn't be opposed to trying to find another keyboard, just to rule that out as an issue, if someone could suggest a known compatible model. I really don't think the keyboard is the issue, but I'll look for one if you guys think I should and can suggest a compatible model.

 

Should I move on and make all the same confirmations a made with the TK-II with the left POKEY? Anything else I should try? I'm definitely open to ideas.

 

[+DrVenkman]

16 minutes ago, bfollowell said:

I get either a blank screen or it hangs at the 1088XEL logo. From there, if I press F12, the system will go ahead and boot. I know that "hang" isn't normal though. Once I press F12 and get it booted though, everything seems to work as I would expect it to.

Remind me - have you tried booting without a keyboard attached at all? 

[bfollowell]

You, know, I'm not 100% certain. I believe I have, but I'll check and will let you know what sort of behavior I see.

 

Edited May 17, 2020 by bfollowell
Add additional info

[bfollowell]

OK, I tried booting with the keyboard disconnected. It exhibited the same behavior, except I obviously couldn't proceed since I didn't have the keyboard connected. It just hung up at the 1088XEL logo, which I should also mention was really, really dim, not bright white like I see when others boot in their videos. It's like it's hanging before the logo is fully on the screen. It's a really dark, dark gray, easily missed if you don't look from the right angle. If you weren't really paying attention, you could easily miss the logo altogether and think it was just a black screen.

[+DrVenkman]

7 minutes ago, bfollowell said:

OK, I tried booting with the keyboard disconnected. It exhibited the same behavior, except I obviously couldn't proceed since I didn't have the keyboard connected.

That *should* rule out any keyboard issues - the machine SHOULD boot fine, to whatever your last-used profile settings were setup for in the BIOS. So I think it's safe to set that possibility aside. 

[flashjazzcat]

The logo does a fade-in, so the system locked up within a second of power-up.

[bfollowell]

OK, to add a little more detail, I get some occasional graphic corruption on the screen. I'd say it happens 10-20% of the times I boot. The other times, it seems like a somewhat normal looking boot with the exception of hanging up and requiring me to press F12. When I do get the screen corruption, another press of F12 clears it and the boot will proceed normally from that point.

 

This first one is major screen corruption and something like this, when it happens, is typically after the board has sat unpowered for two or more hours with the power connector completely removed. I should mention that I don't always get this even after that board has been down for days. Sometimes I'll see a somewhat normal boot. The only time I see this particular amount of corruption though, is after a fairly long down time. Pressing F12 again will clear it right up and take me right back into a good boot though.

 

 

 

These next several are just common little bits of screen corruption that I sometimes see at boot. Again, sometimes it will go right on through, and sometimes it will require a second F12 press to boot properly.

 

 

 

 

 

 

This last one is even more odd. Where most of the others boot into SDX or the U1M menu, this one just randomly boots right into the XL self-test mode.

 

 

 

 

I should also mention that, regardless of whether or not I get screen corruption, or the amount, once I finally get booted properly, the machine acts normally and I can even reboot from the U1M menu and will not experience these issues again until I cold boot again. A warm boot doesn't seem to experience any of these same issues.

 

[+DrVenkman]

So since you’re getting lockups even without a keyboard attached, and very early in the process, we need to consider what’s going on at boot. 

 

The clock starts oscillating; that “tickles” GTIA into producing the FPhi signal to ANTIC to start processing display list instructions and GTIA to produce a video signal; the Phi0 signal from ANTIC then goes to SALLY to boot the machine.  Do you have a spare SALLY to try? Do you have spare logic chips for the clock and memory support? I don’t have a schematic handy for chip references, sorry! 

 

I’m just wondering if you have a marginally-out of spec chip that’s just causing issues once in awhile.

[larryleffaovell]

20 minutes ago, bfollowell said:

OK, to add a little more detail, I get some occasional graphic corruption on the screen. I'd say it happens 10-20% of the times I boot. The other times, it seems like a somewhat normal looking boot with the exception of hanging up and requiring me to press F12. When I do get the screen corruption, another press of F12 clears it and the boot will proceed normally from that point.

 

This first one is major screen corruption and something like this, when it happens, is typically after the board has sat unpowered for two or more hours with the power connector completely removed. I should mention that I don't always get this even after that board has been down for days. Sometimes I'll see a somewhat normal boot. The only time I see this particular amount of corruption though, is after a fairly long down time. Pressing F12 again will clear it right up and take me right back into a good boot though.

That's very similar to my situation I mentioned here.

Notwithstanding this I've checked the signal quality of PHI2 today what @tf_hh and @DrVenkman suggested, and according to tf_hh PHI2's signal quality is rarely looking good. His next advice is to check of the signal of 6502's pin #7. Well, learning (an oscilloscope) by doing...

Edited May 18, 2020 by larryleffaovell
image added

[bfollowell]

39 minutes ago, DrVenkman said:

So since you’re getting lockups even without a keyboard attached, and very early in the process, we need to consider what’s going on at boot. 

 

The clock starts oscillating; that “tickles” GTIA into producing the FPhi signal to ANTIC to start processing display list instructions and GTIA to produce a video signal; the Phi0 signal from ANTIC then goes to SALLY to boot the machine.  Do you have a spare SALLY to try? Do you have spare logic chips for the clock and memory support? I don’t have a schematic handy for chip references, sorry! 

 

I’m just wondering if you have a marginally-out of spec chip that’s just causing issues once in awhile.

 

I have a spare Sally from my 800XL, as well as any other socketed chip in my 800XL. That being said, I'm fairly certain that I've already swapped ANTIC, GTIA and SALLY at different points in my troubleshooting and had the same results. I can try again though.

 

32 minutes ago, larryleffaovell said:

That's very similar to my situation I mentioned here.

Notwithstanding this I've checked the signal quality of PHI2 today what @tf_hh and @DrVenkman suggested, and according to tf_hh PHI2's signal quality is rarely looking good. His next advice is to check of the signal of 6502's pin #7. Well, learning (an oscilloscope) by doing...

 

I will add these points to my troubleshooting log as to-check items and see what they look like.

 

[larryleffaovell]

30 minutes ago, bfollowell said:

I will add these points to my troubleshooting log as to-check items and see what they look like.

 

Good guy  I didn't and getting confused now what I've already did and what I haven't done.

Meanwhile I've checked CPU's pin #7/SYNC: It's acting fine for 10 seconds and going to Low then. I'll just wait for further >=30 seconds then, press F12 and voila, system is up and stable.

 

[+DrVenkman]

There’s a lot of ground noise “ringing” in your scope traces. Try to ground your probe as close to your measurement point as possible to get a better idea how much of that noise is real noise in the ground plane versus noise in the measurement process. 

 

— 

That said, my XEL is closed up with my CF card reader and activity light panel all wired up. I’d have to take it apart and unplug everything to be able to make any comparison traces for folks. My XLD is much more accessible, frankly. Any readings would be analogous but not necessarily perfectly comparable. 

[bfollowell]

OK, I've checked out several of the signals you guys mentioned and have screenshots from my scope. Keep in mind that I've only had this scope for about a week and have only played with it a few times. Also, my last real experience with a scope goes back to college over thirty years ago.

 

Anyway, I checked pin 7 on the CPU, the clock, and here's what I got.

 

This image is of the clock at the point that the boot process freezes at the 1088XEL logo

 

 

 

This image is of the clock after I've pressed F12 and the system had booted into SDX

 

 

 

I wasn't 100% certain what you guys were referring to as Phi2. I couldn't find that anywhere on the 1088XEL schematic, but I did find PH2 on the CPU, ANTIC and GTIA. These are all images, in order, of those three signals. They all looked fairly similar, and they didn't change from before and after the boot freeze.

 

CPU:

 

 

 

ANTIC:

 

 

 

GTIA:

 

 

 

Edited May 20, 2020 by bfollowell

[+DrVenkman]

39 minutes ago, bfollowell said:

Anyway, I checked pin 7 on the CPU, the clock, and here's what I got.

Pin 7 of SALLY isn’t the clock, it’s the SYNC signal, which isn’t really the same thing.  The clock input to SALLY is PHI0, generated by ANTIC. That’s used internally by the 6502 core to generate the output signals used to clock the rest of the system, Phi1 on pin 3 (which really isn’t used), and Phi2 on pin 39, which is used by EVERYTHING, basically. These two signals will be out of phase with one another. I have scope pics of what all these look like in a healthy A8, but they’re on my PC and I’m posting now from my tablet.

 

Now, that said, your Phi2 (PH2) traces look weird - they should have much smoother baselines, not that angled/trailing off business you’re seeing. It’s almost as if there’s something lagging, trying to keep the signal high rather than letting it drop back to ~0V smoothly. 

Edited May 20, 2020 by DrVenkman
typos

[+mytek]

In the XEL (and the same for a stock A8) Phi1 is used to generate a voltage doubled output for the color adjustment POT (check out the video section in the schematic).

 

[+DrVenkman]

8 hours ago, mytek said:

In the XEL (and the same for a stock A8) Phi1 is used to generate a voltage doubled output for the color adjustment POT (check out the video section in the schematic).

 

Yep, that’s true. I was thinking in terms of the traditional “clock” signal used to synchronize all the rest of the chips in the system. I realized/remembered Phi1 is used for the CADJ circuit last night when I consulted SAM’S to help someone else with color issues on their 800XL.  

 

That said, I still think bfollowell’s Phi2 signal looks pretty janky on the low end, like something is “stuck” and trying to prevent the signal from going low properly. 

[+DrVenkman]

Okay, I was thinking about this all day - I still think there's something janky with bfhollowell's Phi2 signals. Couple points - the traditional 6502 signals are Phi0, generated by ANTIC and provided to SALLY, and Phi1 and Phi2, generated internally by SALLY. Phi1 is pin 3, Phi2 is pin 39. On the XEL design, Phi2 is buffered by the 74F08 chip and "BF2" ("Buffered Phi2") is the signal provided to the system chips. Michael can probably describe it more eloquently, but buffering the signal is intended to provide sharper rise and fall times, since most of the functions that use the signals are based off the rising or falling edges. It also introduces a tiny bit of delay which can be useful for timing matters, and it's also supposed to give cleaner highs and lows for each pulse.

 

So tonight I opened up my XEL pulled things apart as much as I could without unplugging things like the CF-3 interface. I made measurements of the BF2 signal on pin 7 of the left POKEY, as that's the one the one used for keyboard and SIO functions, so any signalling issues would be most critical there. I was going to try to compare it to the raw Phi2 output on SALLY, but in my system, to access that side of the chip I'd have to unplug my CF-3 interface, then reassemble it all later. So I did the next best thing: I measured Phi1 on pin 3, which I could get to easily. These two signals, Phi1 and Phi2, are offset by approximately 180 degrees of phase so while one is high, the other will be low and vice versa. There's a bit of overlap [for reason] but other than that, they should look generally the same except for phase. Note that SALLY pin 3 and pin 39 are raw signals, not buffered - they're right off the chip. Comparing the traces below shows what buffering the signal does in terms of nice sharp square waves for timing. 

 

General best practice is to ground your scope probe as close to the signal being measured as possibe. In my case I wanted a worse case and I also didn't want to faff around and accidentally ground something inside the tight confines of my machine, so I used a pre-made jumper wire with male and female Dupont connectors as my ground. I plugged it into the ground pin of one of the auxiliary power jacks at the far right of the board and used the probe alligator clip to grab the male pin of the wire. This adds a lot of capacitance and noise and so should give me as noisy a reading as possible, especially measuring pin 7 of a POKEY, clear across the board. 

 

Now with all that out of the way, this is what the BF2 signal on pin 7 of the system Left POKEY should look like in a properly running XEL, and what the Phi1 output on pin 3 of SALLY should look like, for comparison. I made captures with and without cursors (and yes, I see now that I have the two Y-axis lines out of order so the amplitude is negative. Ignore that. ) 

 

The fact that the buffered Phi2 signal to your chips has a sort of lingering, dragged-out fall to baseline makes me wonder if either your F08 chip is defective, or if there's something else in the signal chain that's preventing a clean falling edge. 

 

Buffered Phi2 (B02), measured on L-POKEY, pin 7:

 

 

Buffered Phi2 (B02), measured on L-POKEY, pin 7:

 

 

Phi0 (PH0), measured on SALLY, pin 3:

 

 

Phi0 (PH0), measured on SALLY, pin 3:

 

Edited May 21, 2020 by DrVenkman
typos, clarity, pic captions

[+mytek]

1 hour ago, DrVenkman said:

Okay, I was thinking about this all day - I still think there's something janky with bfhollowell's Phi2 signals. Couple points - the traditional 6502 signals are Phi0, generated by ANTIC and provided to SALLY, and Phi1 and Phi2, generated internally by SALLY. Phi1 is pin 3, Phi2 is pin 39. On the XEL design, Phi2 is buffered by the 74F08 chip and "BF2" ("Buffered Phi2") is the signal provided to the system chips.

Thanks for detailing all of this Herb ? .

 

And to avoid any confusion, on all my schematics I use the following abbreviations for the clock signals.

PH0 = Phi0

PH1 = Phi1

PH2 = Phi2

B02 = Buffered Phi2 via single gate in 74F08 high speed quad AND gate

 

 

PH1 is used to drive a voltage doubler circuit for the Color Adjustment POT, so I'm pretty sure part of the reason it might look less than ideal on the scope would have to do with the loading and capacitance of that circuit.

 

 

 

[bfollowell]

5 hours ago, DrVenkman said:

Okay, I was thinking about this all day - I still think there's something janky with bfhollowell's Phi2 signals. 

 

That says a lot right there. It makes me feel bad, and very good at the same time.

 

I mean, I'm working every night, sleeping half the day, and spending much of my free time trying to get another rental house my wife and I have purchased ready to go as well as spoiling our newest grandson as much as possible. I only get odd bits of time here and there on the weekends to tinker, and here you are thinking all day about my problem! I feel a little bad, but also very good knowing that I have friends on this forum that are willing to go out of their way to help when needed. I want you to know that I really appreciate it.

 

I'll use the same measurement points and play with my scope some over the holiday weekend and compare my waveforms to yours. I'll also check out the 74F08 as well, in case there's a problem with the soldering, install or socket.

 

 

3 hours ago, mytek said:

And to avoid any confusion, on all my schematics I use the following abbreviations for the clock signals.

PH0 = Phi0

PH1 = Phi1

PH2 = Phi2

B02 = Buffered Phi2 via single gate in 74F08 high speed quad AND gate

 

 

PH1 is used to drive a voltage doubler circuit for the Color Adjustment POT, so I'm pretty sure part of the reason it might look less than ideal on the scope would have to do with the loading and capacitance of that circuit.

 

 

 

 

Thanks for clearing up the signal abbreviations. Those were kind of what I'd assumed those were, but it's good to know for certain.

 

Edited May 21, 2020 by bfollowell

[+DrVenkman]

Don’t feel bad - it’s a nice distraction to think of someone else’s problems instead of my own.  Anyway, just to rule out any issues with the measurements, I want to point out that it can be tricky to measure signals in a closely-packed system. As I noted above, the ground I used was a simple pre-made jumper wire clipped to the ground lead of my probe and plugged into the ground lead of one of the auxiliary power headers on the board.  To pick up signals from the chip or component I’m interested in, I use a feature that is not necessarily obvious to someone who hasn’t used an oscilloscope for long - on most o-scope probes, the contact end is a little retractable micro-clip you can grab a wire or resistor leg with ... but you can usually pop the plastic end of the probe right off, exposing a slender metal pin for point measurements. So for XEL measurements, I set that fine metal point on the shoulder of the chip pin that I want, with the ground lead to the probe connected as above. Then I set the scope running to grab measurements - moving the probe around will affect the signal so I let it run for a couple seconds to make sure things I’m measuring are actual signals and not noise added by wiggling the probe or ground. Then I hit RUN/STOP on the scope to freeze it so I don’t have to worry about holding the probe so carefully and still, and I can look at the signal at leisure. 

 

So apologies if the above was already known or obvious. I had to re-learn how to use a scope last year after not having had access to one since college 30+ years ago and I wanted to try to help ensure you’re getting the best signals you can just in case measurement issues might disguise any other real problems hiding underneath.