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Mark Simonson

800XL SIO port stopped working

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I've got an 800XL that I bought new in 1985 and have used sporadically since the eighties. I've started using it again recently after acquiring an SDrive-Max and an Ultimate-A8 SD cartridge and making an SIO2PC-USB cable to hook it up to my Mac running AspeQt. Everything was working great until today when the SIO port on the 800XL seemed to stop working. 

 

I tried various devices on the SIO port, including my original 1050 and another 1050 I bought recently, using different SIO cables, using the above-mentioned devices. None of the pins are bent or anything. It won't boot from any of these. It behaves as if nothing is plugged into the port. Just the old "raspberry" you get when you start up when there's no device to boot from.

 

I was only able to find a couple of discussions where SIO port failure seemed to be the issue. One possibility suggested was a bad power supply. I checked the voltage coming out of my (1985) 800XL power supply, but it appears to be okay, with a steady 5v DC, so I'm guessing it's probably not that. This kind of leaves it to be some sort of problem with POKEY.

 

Is there any way to test whether it actually is a POKEY problem? Keyboard and sound still work, FWIW. Any other possibilities for an SIO port problem like this? Could one of these newfangled devices I've been plugging into it recently have damaged the port or the POKEY chip?

 

FWIW, my machine has a socketed POKEY chip. I have very little experience with working on electronics hardware, but I think I would be able to handle replacing the chip, if that's where the problem is.

 

Edited by Mark Simonson

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Is it possible that the solder joints on the SIO socket in your 800XL may have cracked, can you re-flow the solder

to these first, may just be the inserting/removing plugs has weakened the joints.

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I don't know if this is useful, but when the SDrive-Max is connected, the little status window prints "SIO:CMD Timeout" whenever I switch off the Atari.

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Could be the 6520 PIA chip.  The SIO command line is driven by the 6520 PIA.

 

Are the chips in your 800XL socketed ?  Do you have another you can borrow the PIA from for testing ?

 

 

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Also.... make sure your power supply is not the dreaded 'ingot'.  Search for ingot power supply in the forums and you should find posts about it.

 

If you have a multimeter check your power supply voltage.  It should 5.0-5.2V ideally.   While that won't stop the SIO from working, if the PIA has popped, you'll want to make sure it is not from a bad power supply sending too much voltage into the XL.... or you'll start blowing Sally, Antic, GTIA, Pokey, ram, etc.

 

 

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sounds like the sdrive Max is getting power but no signal

check the middle pin on the bottom row of the SIO port (it is named 'command') and any associated components. if nothing looks damaged, maybe the chip that manages the SIO port could be the culprit? The PIA chip pin 19 is listed as 'SIO Command' but im sure the pokey chip also has some influence over the port..

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The SDrive-Max is getting power externally via USB, not the SIO port.

 

Most of the big chips in my 800XL are socketed, but not the PIA unfortunately. I would not attempt to replace this myself, as it's way beyond my skills.

 

I indeed have the "dreaded 'ingot'" power supply. As I mentioned, it shows exactly 5.0v when I checked it with my volt meter, but maybe that's not always the case?

 

In any case, I ordered a new power supply cable that connects to a USB source, as I have heard these old power supplies can be a problem.

 

I suppose the easiest (if not cheapest) fix is to buy another 800XL off eBay. It bums me out that my original one might be borked, possibly from the old power supply. It's always been a champ until today. And just when I was getting back into using it and doing some really cool stuff.

Edited by Mark Simonson

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There are some great legacy power supplies out there.  Best Elect sells them.  Of course, there are modern options as well (The Brewing Co.,etc.).  Ingots are killers for sure.  But, luckily our 8-bits are very fixable, and for the most part, the components are readily available.  There may be some motherboards available if you like your old keyboard.  Sometimes it is cheaper to buy a serviceable unit.  Then you have parts to use for future troubleshooting ventures.  I guess that is why I several backups.  Too many.  

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The USB power cable I ordered is from The Brewing Co.

 

How common is it to get 800XLs with socketed chips? Are they usually socketed or usually not? I'm wondering because I recently ordered a Sophia video upgrade (also from The Brewing Co.). I wouldn't have done so if the GTIA on my 800XL wasn't socketed. If I decide to replace the whole machine, I'd want to make sure to get one with a socketed GTIA at least so I can install the Sophia.

Edited by Mark Simonson

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Most of my XLs have been socketed.  I know there are statistics available.  Have you opened you XL up to look?  If you have a socketed XL, then you can probably easily re-seat the chips (observe proper static electricity protocols--social distance your electrons).  That may even solve your issue. Oxidation over years on the socket pins.

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Most of the larger chips are socketed, except for the PIA and the RAM. Thanks for the suggestion. I'll give that a try.

 

Edit: I pulled out POKEY and reseated it. SIO still non-functional.

Edited by Mark Simonson

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It looks like POKEY chips are somewhat available, and I'd be willing to buy one, but I'm wondering if there is any diagnostic program that can tell if the POKEY chip is still working? I'd hate to order one only to find out that it's not the problem.

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I've run into the same problem you have with one of my 1200XL's. I believed I had a bad POKEY but it in fact turned out to be a bad POKEY socket - since your POKEY is socketed, I suggest you remove it and look closely at the chip from every conceivable angle, including from either end along each row of pins. Ensure that you don't have a corroded or damaged chip leg, and that all of them are at the same or extremely similar angles to ensure each leg makes good contact in the socket. Next, look very closely (magnification and bright light help here greatly) at the socket itself. Do any of the socket contacts ("wipes") appear dirty, corroded, bent or broken? If there is any debris or corrosion visible, try cleaning with a nylon toothbrush and isopropyl alcohol and then re-seating the chip.  In extreme cases, you may find a socket wipe that has gotten bent and no longer makes good contact with the chip leg, or worse - a wipe that has actually broken.

 

 

IMG_8314.JPG

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FWIW, it seems weird that would be working every day for the last month (last time I used it before that was three or four years ago) and then suddenly fail today if it was a bent pin or something. I didn't see any corrosion or bent pins or dirt anywhere when I pulled it out earlier this evening. In fact, this is the first time the POKEY has been pulled out since it was new. Further, I never even opened the machine until about two weeks ago since I bought it in 1985. It's always been stored indoors in dry, smoke-free areas. Barely any yellowing on the plastic.

 

The only thing I can think of is that running it every day for the last month (after being dormant for years) pushed some aging component past the failure point. Then there's that notorious power brick.

 

Still, thanks for the suggestion. I'll take another look at the socket to make sure.

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Inspect the capacitors for leaking or bulging.  Although, I have not seen this to be a real issue for the Eights.  When you are inspecting the wipes on the sockets, turn the board over and go centimeter by centimeter inspecting all the solder joints with a magnifying glass.  Sometimes you can simply re-flow the solder joints and that will correct any continuity issues (cold, or fractured solder points).  Point in case on the XF-551's board, fractured solder joints are often the culprit.  Sometimes you can see the fractures, sometimes not.  Reflowing is a good thing with a proper soldering device. 

 

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Thanks for the advice, although I don't think I'll attempt to reflow any solder. I've barely ever done any soldering in my life and I'd likely make it even worse. It's starting to look like fixing it myself is more than I can handle. No doubt, I could probably learn, but at my age, there are other things I'd rather do with my time.

 

However, I know there is still an active Atari group in my area (S.P.A.C.E.) so maybe I'll contact them and see if there's someone local who could look at it and maybe repair it.

 

In the mean time, I think I'm just going to buy another 800XL so I can get back to having fun.

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16 hours ago, Mark Simonson said:

I don't know if this is useful, but when the SDrive-Max is connected, the little status window prints "SIO:CMD Timeout" whenever I switch off the Atari.

That is what it should say when it losses the signal. 

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