My 1200XL is cursed, need it completely reconditioned.

[tschak909]

Sigh.

 

I am at the end of my rope.

 

If I could fix this system myself, I would. My cerebral palsy prevents me from working on hardware in earnest.

 

A bit of history.

 

Bought an Atari 1200XL from @sloopy with an original Ultimate 1MB inside it.

 

Accidentally flashed it with @flashjazzcat's BIOS, without a corresponding JEDEC update. Could not get a working CPLD reprogramming rig to work, so I bought another U1MB, plopped it inside, and sent the original back to @sloopy

 

Sent the machine to Brian Weiser, who plopped the UAV I had in the system, he re-capped the machine as well, and sent it back.

 

System worked great for a few months, before the following symptoms appeared:

 

* Freezing

* when frozen, system would freeze at a green or red screen if attempted to cold start. System would need to sit for a few hours, and then it would be fine again.

* over time the intervals between stability and crashing would decrease.

 

In addition, GTIA output was incorrect, the top most luminance bit was missing.

 

Sent to @Paul Westphal at 8 bit fix, who put the system on his SALT rig.

 

He tested it for almost a week, ultimately found a bad PIA test result, replaced PIA. Was about to send it back to me, when the above mentioned symptoms re-appeared. System would eventually not boot at all.

 

I paid him for his time, and he sent the machine off to Marlin Bates at @MacRorie, who diagnosed a mis-configuration with the UAV, as well as some solder re-flowing and capacitor re-positioning. He sent the machine back to me after a 6 hour burn-in.

 

I got the machine back, today, turned it on, worked great for roughly 3 hours, and then froze, and is now unable to cold start.

 

I need someone versed well enough in logic level diagnostics to see WHAT'S happening, and why, and to please, FIX IT.

 

THIS IS MY #FUJINET DEVELOPMENT SYSTEM, AND IT NEEDS TO WORK, and I am being reduced to tears, because I can't keep borrowing hardware when I ship this thing out!

 

CAN. ANYONE. ACTUALLY. HELP?!

 

-Thom

 

[+MrFish]

Why not just purchase another machine that's in working condition, so you can get the 1200XL attended to without the pressure of it being your only machine? At that point you could even just put the 1200XL aside for a while, to relieve the frustration.

 

[+mytek]

4 minutes ago, MrFish said:

Why not just purchase another machine that's in working condition, so you can get the 1200XL attended to without the pressure of it being your only machine? At that point you could even just put the 1200XL aside for a while, to relieve the frustration.

That's a good idea. You might want to touch bases with @bob1200xl . He's got the market covered on 1200XLs and has been fulfilling people's needs lately with extra stuff He's willing to part with.

 

[+bob1200xl]

I can send you a new motherboard.

 

Or, two...

 

Bob

 

[tschak909]

3 minutes ago, bob1200xl said:

I can send you a new motherboard.

 

Or, two...

 

Bob

 

That would be great.

-Thom

[cwilbar]

The sorts of issues described here do sound like potential PCB issues (cracked trace, through hole plating break, etc). 

 

One thing I ran into (with an 800XL) was that the system had odd issues powering up (freezing with single color screen, occasionally other behavior).

I found that when I had the upper RFI shield off, it worked flawlessly every time.  I don't know that if this can happen in an 1200XL, but the 800XL I worked on, what was happening is the right side of the shield a the front was shorting against one of the resistor legs in that area and preventing the machine from operating.

 

I don't think you've got the same case... but it might not hurt while you seek/wait for a replacement board/system.  You never know.  A year ago I'd never have even thought of trying it.... and in my case I figured that out in mine by pure accident (and thankfully made the connection so I could finally figure out what was happening).

 

Best of luck.... sounds like a very frustrating situation (I have a couple of 1050s I need to get back to that have frustrating issues to locate.... so I moved onto other things for a while).

 

 

 

 

[+JAC!]

In fact for me it also sounds like a power supply issue. Hardware modifications comsume more power and the power supplies/regulators may change their behaviour after some hours of operation. Even some mV can make a difference then.

[Donald Dennis]

On 9/22/2020 at 7:16 PM, JAC! said:

In fact for me it also sounds like a power supply issue. Hardware modifications comsume more power and the power supplies/regulators may change their behaviour after some hours of operation. Even some mV can make a difference then.

As a matter of fact, I just finished addressing the power issue. On my 800XL, I was experiencing the "Birdie" phenomenon with Side 3 and U1MB. I was running it on a 2.4 amp USB power supply. Switching it over to a 3 amp power supply provided resolution to that issue.

I was experiencing similar "phenomenon" with my 1200XL and upon further investigation discovered it required a little different approach but was fully doable. The 1200XL is powered by the same 9VAC transformer the 400/800 and many peripherals are. It turns the 9VAC into I think 12VDC which is then regulated down to 5VDC by a pair of LM340T regulator IC's. The LM340T is rated at 500 milliamps which was likely sufficient back in the day when all that was being plugged into one was a ROM cartridge.

I theorized that with U1MB installed, and running a Side 3 cartridge that most likely pulls more current than a standard ROM cartridge that a combined output of 1 amp between the two regulators was most likely not going to be enough to power all of that. I was experiencing "Birdies" and random lock ups which could be attributed to system instability and I also performed all the recommended logic chip replacements (74F138 & 74F08 in place of 74LS138 & 74LS08), switched out ANTIC chips and CPU's, added the capacitor across the proper terminals on the U1MB board etc. All that served to mitigate the problem somewhat but did not eliminate. I eventually ended up on the power supply track, taking inspiration from what I had done with my 800XL and replaced the two LM340T's with a pair of LM7805CV's which are rated at 1.5 amps each effectively tripling the current capacity of the original configuration.

Thus far to date, both my 800 and 1200XL have been extremely well behaved and exhibit no instability issues.

It took me almost a year to the day of my first U1MB install tinkering and piddling and tweaking in spare time to discover this so I'm hoping it helps save some trouble for my fellow Atarians.