1088XEL Atari ITX Motherboard DIY Builders Thread

[+Eyvind Bernhardsen]

Thanks for the suggestions! It’s getting late here, but now I have a checklist for tomorrow.

[+DrVenkman]

1 hour ago, MacRorie said:

Here's my "something went 'kaka' checklist":

(SNIP)

8.  Prayer, Mr. Saavik, the 1088 don't take prisoners.

 

 

[+mytek]

Kirstie Alley was the best pick for a vulcan besides Lenard Nimoy at the time. Too bad that she didn't reprise her role in the movies that followed.

 

[+Eyvind Bernhardsen]

20 hours ago, Stephen said:

Next thing I would check, is plug in a set of external speakers and see if you get anything at all when powering on.  A click, hum, etc.

There's a click when I push the power button (along with some out-of-sync white scanlines on the screen that disappear in less than a second), and fairly low buzzing while the power is on. Could be just analogue noise, I can only hear it with the volume turned all the way up.

 

20 hours ago, MacRorie said:

1. Check and touch re-flow all solder points on the bottom (maybe you missed *A* pin or got a cold solder somewhere or a small small bridge)

Re-flowing is the one I'm dreading (so many solder points...) so I've started looking at everything else first. I've looked over with a loupe, can't see any bridges or missed pins. All ICs and their sockets are aligned according to the silk screen and inserted correctly, no bent pins. For the SIP resistor networks, I assume the end marked with a dot or line is pin 1 and should go into the individually boxed hole on the PCB?

 

The U1MB has worked perfectly in my XEGS for years, and I've never repaired it; I believe all first generation Candle U1MBs came that way "from the factory." I've been carefully aligning it using the header pins (since they're not shrouded) every time I put it in. UAV is previously untested, but since there's no sound I don't think the problem is just in the video circuit.

 

I only have two jumpers on the board, one for PAL and one on the oscillator pins (J20). I ordered three jumpers as the BOM instructs, but I don't know what the last one is for.

 

Does swearing count as prayer? There may have been some of that.

 

The most likely candidates for being bad are the 40 pin ICs from the 800XL, but I don't have any replacements except the ones in my XEGS. I've verified that POKEY works since it's socketed in the XEGS, but I'd rather not desolder any of the other chips for fear of ending up with zero working Ataris.

 

I suppose I'll just have to warm up the soldering iron.

[+Firedawg]

Make sure on your board that all the through holes received enough solder to sufficiently flow threw the vias to complete the solder joint.  I believe that was an issue that gave a few boards a rough start.  So look at the component side as well.

[+Eyvind Bernhardsen]

44 minutes ago, Firedawg said:

Make sure on your board that all the through holes received enough solder to sufficiently flow threw the vias to complete the solder joint.  I believe that was an issue that gave a few boards a rough start.  So look at the component side as well.

Hmm, some of the joints are a bit thin on solder. I’ll do those first. Thanks!

[flashjazzcat]

22 hours ago, MacRorie said:

R & R daughterboards (U1M, UAV) especially since that U1M has been repaired.  At least I am assuming it has been repaired since there is an empty pin and a jumper wire on the MMU connection.

That via was left unoccupied on the original boards since there is no pin in that position on the connector. The jumper wire is certainly non-standard, however.

[+DrVenkman]

8 minutes ago, Eyvind Bernhardsen said:

Hmm, some of the joints are a bit thin on solder. I’ll do those first. Thanks!

Do you happen to have access to a logic probe or oscilloscope? Those can really help you focus in on hardware problems. Alternately, and apologies if you've already verified this and I missed it in an earlier post, but have you verified a good 5VDC on the Vcc pins for the chips on the board? If you get significantly LESS than that, there's a decent chance you've got a small short or defective chip somewhere on the board, maybe even something as small as a flake of solder between a couple pins under a socket.

 

[+mytek]

2 hours ago, Eyvind Bernhardsen said:

I only have two jumpers on the board, one for PAL and one on the oscillator pins (J20). I ordered three jumpers as the BOM instructs, but I don't know what the last one is for.

Jumpers: J21 - PAL/NTSC, J20 - OSC, J4 - SIO2PC handshake (DSR, RI, CTS)

 

[+Eyvind Bernhardsen]

1 hour ago, DrVenkman said:

Do you happen to have access to a logic probe or oscilloscope? Those can really help you focus in on hardware problems. Alternately, and apologies if you've already verified this and I missed it in an earlier post, but have you verified a good 5VDC on the Vcc pins for the chips on the board? If you get significantly LESS than that, there's a decent chance you've got a small short or defective chip somewhere on the board, maybe even something as small as a flake of solder between a couple pins under a socket.

 

Thanks. I did verify just over 5V on the power pins of each IC socket before populating the board (only soldered components and the 555 present), haven’t verified the voltage under load because I’m worried about shorting pins with the multimeter probes.

 

No oscilloscope, unfortunately. This might be an excuse to get one...

[+Eyvind Bernhardsen]

25 minutes ago, mytek said:

Jumpers: J21 - PAL/NTSC, J20 - OSC, J4 - SIO2PC handshake (DSR, RI, CTS)

 

Ah, thanks! I still haven’t put the sio2pc board in, so I’ll put the handshake signal decision off for a while

[+DrVenkman]

1 minute ago, Eyvind Bernhardsen said:

Thanks. I did verify just over 5V on the power pins of each IC socket before populating the board (only soldered components and the 555 present), haven’t verified the voltage under load because I’m worried about shorting pins with the multimeter probes.

 

Here's a good trick to prevent worry about shorting - clip a wire or use a jumper with a female Dupont header on it and connect to one of the auxiliary power connectors over on the right side of the board. Connect that wire to the ground pin of the connector and use that as the ground for all your board voltage measurements. That way you've only ever got one meter probe (your positive probe) around the chips at a time. Measure the voltage on each chip by just touching the top of the chip shoulder - should be safe and easy. 

[+Eyvind Bernhardsen]

Small update: My procrastination on re-soldering everything led me to buy a Hz-measuring multimeter, which revealed that both PAL and system clocks look okay on GTIA pins 16 and 28.

 

Using Dr. Venkman's trick I also measured Vcc on all ICs except the 6520 (because it's under the U1MB) to 4.96V with a full board. Is that acceptable?

 

[+mytek]

1 hour ago, Eyvind Bernhardsen said:

Using Dr. Venkman's trick I also measured Vcc on all ICs except the 6520 (because it's under the U1MB) to 4.96V with a full board. Is that acceptable?

Yep that's pretty normal for the XEL.

 

[+Eyvind Bernhardsen]

Progress! My previous soldering iron could only barely melt RoHS solder, so I got myself a proper one and reflowed the dodgier-looking joints, but that didn't have any effect.

 

On a whim I swapped out the 64K SRAM chip (which the seller unexpectedly sent me two of... possibly foreshadowing), and now I get the U1MB boot screen! Unfortunately the progress bar only makes it about half way before the system restarts with a speaker click, and the second time around it barely gets started before the system locks up completely, again accompanied by a speaker click, with the frozen progress bar left on the screen.

 

The behaviour is more or less reproducible: the bar doesn't always make it halfway before it resets, and sometimes it freezes without resetting at all. Is there actually anything going on in the background, or is the progress bar just there to let the user see the splash screen?

 

I'm still on the normal (non-1088) U1MB firmware, if that matters.

[flashjazzcat]

17 minutes ago, Eyvind Bernhardsen said:

Is there actually anything going on in the background, or is the progress bar just there to let the user see the splash screen?

Absolutely nothing is happening when the progress bar is filling up, so it appears the system is crashing arbitrarily.

18 minutes ago, Eyvind Bernhardsen said:

I'm still on the normal (non-1088) U1MB firmware, if that matters.

Not really; you will be missing some features, but it should boot.

[+DrVenkman]

2 minutes ago, flashjazzcat said:

Absolutely nothing is happening when the progress bar is filling up, so it appears the system is crashing arbitrarily.

Jon, you might remember details of this better than I do, but wasn’t that added basically to help kill time to account for the different lengths of time it takes various PS2 keyboards to initialize? 

[+Eyvind Bernhardsen]

33 minutes ago, flashjazzcat said:

Absolutely nothing is happening when the progress bar is filling up, so it appears the system is crashing arbitrarily.

Not really; you will be missing some features, but it should boot.

Thanks for the information, that's about what I expected. I'm not sure dodgy RAM would cause this kind of predictable crash, so I'm guessing that this is caused by something I've done wrong.

 

Investigations continue, meanwhile I'm just happy I finally got an image on the screen

[flashjazzcat]

40 minutes ago, DrVenkman said:

Jon, you might remember details of this better than I do, but wasn’t that added basically to help kill time to account for the different lengths of time it takes various PS2 keyboards to initialize? 

The fade-in before the progress bar starts moving was added for this purpose Herb, yeah. That initial delay happens regardless of whether the splash screen is displayed or not, too, so if you power-on with Help pressed and wait long enough, you should go straight to the setup menu even if the logo is turned off.

 

[+Eyvind Bernhardsen]

Update: I ordered a couple of UM61512As from a different eBay seller on a hunch that the second RAM chip was also flaky. They arrived today, and when I swapped one in the XEL is much healthier! The U1MB setup menu and loader work, I've played some games (graphics and sound are present and correct), and I've been able to boot into SpartaDOS intermittently, though that sometimes hangs during boot.

 

Once it's started up it can read my CF card just fine, so I would like to get a memory tester on there. I'm open to suggestions as to what else could be wrong

 

[+Eyvind Bernhardsen]

Last night I discovered that the built-in memory test hung after a single green square, which made me think there was a problem with the ROM: the U1MB menu and all the games I tried were stable, while SpartaDOS, BASIC, and the self test acted flaky. Today I realised that while the OS ROM is XEGS, the XEGS jumper wasn't installed in the U1MB.

 

Adding that jumper seems to have stabilised the system! The self-test memory test passed, and I've used SpartaDOS quite a bit without a single hang.

 

Is it expected that running an XEGS OS without the XEGS jumper will cause system instability, or is it more likely that I jiggled something in a lucky way when removing and reinstalling the U1MB?

 

I discovered another thing last night: the video signal in general looks excellent, but the V-gate is absolutely sublime. It's so nice to play Pang without the annoying flicker in the right border. Thanks once again, @mytek 

[+mytek]

2 hours ago, Eyvind Bernhardsen said:

Last night I discovered that the built-in memory test hung after a single green square, which made me think there was a problem with the ROM: the U1MB menu and all the games I tried were stable, while SpartaDOS, BASIC, and the self test acted flaky. Today I realised that while the OS ROM is XEGS, the XEGS jumper wasn't installed in the U1MB.

 

Adding that jumper seems to have stabilised the system! The self-test memory test passed, and I've used SpartaDOS quite a bit without a single hang.

I don't recall ever having a problem like that, although maybe in my case it was the other way around with the XEGS jumper always in place while running other OSs.

 

2 hours ago, Eyvind Bernhardsen said:

I discovered another thing last night: the video signal in general looks excellent, but the V-gate is absolutely sublime. It's so nice to play Pang without the annoying flicker in the right border. Thanks once again, @mytek 

You are very welcome, and I'm glad your system is now working. Yes V-Gate was a pet peeve of mine from several years ago. I just couldn't stand for the graphic garbage that would show up on the out skirts of the intended image. However it has proved to be finicky in relation to the system timing, thus requiring some fine tuning on various systems (e.g., there is a unique version of firmware for the XEL that differs from the XLD).

 

[Smokeless Joe]

On 9/17/2019 at 4:11 PM, mytek said:

I just put the finishing touches on a page of my website that is all about ebiguy's XEL-CF3 Rapidus variant. So for anyone contemplating installing a Rapidus in their XEL, and still wish to have a CF drive, his board is the way to go ? .

 

 

Here's a link: https://ataribits.weebly.com/xel-cf3-rapidus-variant.html

 

I'm building one of these Rapidus variants now.  I searched before asking this question, so please let me know if I missed this anywhere:

 

Comparing the Rapidus variant connections with the original XEL-CF3 here, I see where to connect the CF activity LED on the Rapidus variant, but I don't see where to connect the swap button or the swap button LED.  Am I blind (very possible), are they missing, can I connect them to the MBPI pins, or something else?

 

Thanks!

 

[Smokeless Joe]

Sometimes, the just act of writing things down shakes the rust off the ol' coconut.  From the schematics here, we can clearly see the connections I'm looking for are at J3:

SO the correct answer is "I am blind".

 

Thanks!

[+mytek]

5 hours ago, Smokeless Joe said:

Sometimes, the just act of writing things down shakes the rust off the ol' coconut.  From the schematics here, we can clearly see the connections I'm looking for are at J3:

SO the correct answer is "I am blind".

 

Thanks!

I have a 2nd page to add to the schematic for that board that I need to verify a few things and then update the download. It goes into more detail about all the header pins and what they are connected to. Glad you got it figured out  .