I think I’ve killed my 800XL! Any ideas?

[_The Doctor__]

I haven't re read the thread but two XL's with the same issues worries me about power supply and or common device killing the machines kind of vibe. Please make sure any suspect items don't get used until they are checked out.

[+Peter Rabitt]

Hi Doc. yes I am aware of the p/s problem... I am using 2 different P/s, 1 is a Atari C061982 5v at 1.5 amps...  Probably a little under rated because the first one has a 256k memory upgrade.  I have measured it more than once, about every time I start up.. I also have put the scope on it and very little noise is on it...

The other is a switching 5 v power supply(just bought off ebay or amazon) ..

The first 800xl is from my BBS days 35 or so years ago, and the second one is "new" used from ebay in the last month or so. Was for "parts or repair".. The light comes on but that's all except it have sync and color burst and black screen. Was hopping to find a GTIA or CPU bad and could use it ti fix the old BBS one. It was never opened so I was sad to have to open it...

Yes two delay lines going on two different mach. is very interesting....Have not read about them going bad but there is a thread or two about how to make new ones and the failure of them..Might be a bigger problem than we know

 

Peter

[+Peter Rabitt]

Well good news I got the first 800xl running and checked most of the 40 pin IC I have found a few bad...

I was the delay line and now has the original IC back in it and running the self test all the way...

Going to start on the sec. one next, maybe tomorrow...

 

Peter

[bfollowell]

The crazy summer heat has finally broken here and I'm getting ready to overseed my lawn, so I'll have at least a month with no mowing or other lawn work. I should be able to get back to troubleshooting my 800XL soon. One question. I finally own a digital scope, but it's been decades since I really used one much. I want to confirm that I can use it the way that I want. Since there are two separate channels, can I check and compare two completely different circuits, using one channel for each? I want to use one channel on my good 800XL and one with the bad, and start going through chip by chip, leg by leg, trace by trace, comparing and looking for discrepancies.

 

Any issues with this approach that anyone can think of?

 

Thanks!

 

 

[bfollowell]

1 hour ago, bfollowell said:

The crazy summer heat has finally broken here and I'm getting ready to overseed my lawn, so I'll have at least a month with no mowing or other lawn work. I should be able to get back to troubleshooting my 800XL soon. One question. I finally own a digital scope, but it's been decades since I really used one much. I want to confirm that I can use it the way that I want. Since there are two separate channels, can I check and compare two completely different circuits, using one channel for each? I want to use one channel on my good 800XL and one with the bad, and start going through chip by chip, leg by leg, trace by trace, comparing and looking for discrepancies.

 

Any issues with this approach that anyone can think of?

 

Thanks!

 

 

After a little more looking, I think I found my own answer. It sounds like most oscilloscopes have a common ground between its various channels, so I won't be able to use each channel on a separate circuit as I'd hoped. I'll just have to check one board, then move to the other board and back and forth as I compare. Not a big deal. It just would've been nice to have both waveforms on the screen at once for comparison, but it's not the end of the world.

 

[ECSUSER]

Any update to this thread? As I anxiously await 2 (new to me) 800XL's from eBay, I'm reading hundreds of threads and this one is leaving me wanting more 😆 

 

 

[bfollowell]

No, I haven't had hardly any time to work on this one the past 18 months or so. Coming to cooler weather and the end of outside work season, I'm looking forward to digging into this one, but only time will tell if I actually get to or not.

 

I can't even recall the behavior it was presenting the last time I posted, but it has now moved to just a solid black screen.

 

[bfollowell]

Since this old thread was brought back, I read back through it, just to remind myself of I'd tried and what all had been suggested. Of course, this biggest suggestions were swapping chips to and from other, working, donor machines. The problem was that I really didn't have any at the time. Since then I've acquired a 600XL another 800XL, a 400 and 2 800s, so I have plenty of machines to check chips with, though those didn't seem to be an issue back then. Since I have a whole working 800XL, it shouldn't be too hard so sit with my scope and start comparing signals until I find some differences.

 

One question for those of you more familiar with using oscilloscopes than I am, since it's been a couple of decades since I've spent much time using one and really need to refamiliarize myself with the basics, is do most scopes have discrete or independent channels? In other words, can each channel be from a separate circuit and have its own ground plane? What I'd like to do is connect channel 1 to a point on 800XL #1 and channel 2 to the same point on 800XL #2 so that I can compare them. I thought that might help me look for signal discrepancies to help narrow down my problem.

 

[bfollowell]

2 hours ago, bfollowell said:

Since this old thread was brought back, I read back through it, just to remind myself of I'd tried and what all had been suggested. Of course, this biggest suggestions were swapping chips to and from other, working, donor machines. The problem was that I really didn't have any at the time. Since then I've acquired a 600XL another 800XL, a 400 and 2 800s, so I have plenty of machines to check chips with, though those didn't seem to be an issue back then. Since I have a whole working 800XL, it shouldn't be too hard so sit with my scope and start comparing signals until I find some differences.

 

One question for those of you more familiar with using oscilloscopes than I am, since it's been a couple of decades since I've spent much time using one and really need to refamiliarize myself with the basics, is do most scopes have discrete or independent channels? In other words, can each channel be from a separate circuit and have its own ground plane? What I'd like to do is connect channel 1 to a point on 800XL #1 and channel 2 to the same point on 800XL #2 so that I can compare them. I thought that might help me look for signal discrepancies to help narrow down my problem.

 

 

I didn't look back quite far enough. I was focused on the beginning of the thread. If I'd just looked two posts above, I'd have seen that I answered my own question two years ago, but just never got around to the probing! I'm certain I just spent the past hour or two reading through the same sites all over again!

 

I really MUST make this machine a priority this fall, clean off my work bench and setup both 800XLs side-by-side and start probing for differences.