800XL video issue

[+DrVenkman]

So a month or six weeks ago I did the quick 800XL video fix as described in this thread.

 

http://atariage.com/forums/topic/41580-quick-easy-video-upgrade-for-800xl/

 

It made a great improvement and everything has been working great through my last use, two nights ago. Tonight, however, I powered up my 800XL and get this:

 

 

The monitor is fine - I tested it with another video source to be sure.

 

Anyone have any suggestions for what to look for when I open the 800XL back up tomorrow? Thanks in advance!

[Bryan]

The default text colors are $94 for the background and $CA for the text. If you disconnect the top LUM line, you end with dark text- a brightness of 2 instead of 10.

[Joey Z]

I had a similar issue on a 600XL and it turned out to be a bad 4050. Try swapping a known good one in, and swapping the questionable one into a known good machine. See if the problems transfer along with the 4050. 4050's are a standard part and should be readily available at any electronics distributor.

[morelenmir]

You can get a similar result if the variable resister in the bottom left of the motherboard is incorrectly set. You could try very slowly and carefully rotating it and see if the screen resolves. You will alter your colours doing that.

[+DrVenkman]

Thanks for the feedback, folks. Fortunately, I've got a number of spare machines around, including a previously known-good 600XL I'm using as a chip donor for another machine. Even more fortunately, all the chips in both machines are fully socketed. I'll swap the 4050 and see if the problem persists. If not, I'll check the color resistor, GTIA and ANTIC, in descending order.

 

I really hope it's not the GTIA or ANTIC - I've already pulled those (and POKEY) from my "chip donor" machine to repair a 1200XL. I'd have to order spares from Best in order to avoid sacrificing another machine to the 8-bit Gods.

 

EDIT: So just for giggles, I hit up Jameco for a product search: 39¢ each, lol. I wonder how much shipping would be? More to the point, what else ought I pick up while I'm at it?

Edited July 25, 2015 by DrVenkman

[Joey Z]

Thanks for the feedback, folks. Fortunately, I've got a number of spare machines around, including a previously known-good 600XL I'm using as a chip donor for another machine. Even more fortunately, all the chips in both machines are fully socketed. I'll swap the 4050 and see if the problem persists. If not, I'll check the color resistor, GTIA and ANTIC, in descending order.

 

I really hope it's not the GTIA or ANTIC - I've already pulled those (and POKEY) from my "chip donor" machine to repair a 1200XL. I'd have to order spares from Best in order to avoid sacrificing another machine to the 8-bit Gods.

 

EDIT: So just for giggles, I hit up Jameco for a product search: 39¢ each, lol. I wonder how much shipping would be? More to the point, what else ought I pick up while I'm at it?

what else you should get really depends on what you think you would use. Personally, I'd pick up some DIN 7 connectors, for power supplies, and DIN 5, for video cables. Also DE9's, you can NEVER have enough... though that's less atari related now, since I'm usually not plugging those into the atari, and more often into a PC serial port.

[+DrVenkman]

what else you should get really depends on what you think you would use. Personally, I'd pick up some DIN 7 connectors, for power supplies, and DIN 5, for video cables. Also DE9's, you can NEVER have enough... though that's less atari related now, since I'm usually not plugging those into the atari, and more often into a PC serial port.

 

Those are excellent suggestions - I also see from the VCS Field Service Manual that my Light Sixer uses the same 4050 hex buffer chip, so I'll probably order about 10 of them for my various machines.

 

And as it turns out, it was in fact the 4050 - I pulled that one from my parts-donor 600XL and swapped it in. Voila, problem solved. Thanks, Joey!

[Joey Z]

 

Those are excellent suggestions - I also see from the VCS Field Service Manual that my Light Sixer uses the same 4050 hex buffer chip, so I'll probably order about 10 of them for my various machines.

 

And as it turns out, it was in fact the 4050 - I pulled that one from my parts-donor 600XL and swapped it in. Voila, problem solved. Thanks, Joey!

No problem, like I said, I had the same problem on my 600XL. I think I never ordered the replacement though I have lots of stuff with bad chips in it that I just don't have replacements for, like the bad FREDDIE in my 65XE, there's a bad 4050 in one of them, bad delay line in the same one, some bad DRAMs on my 400's 48K card, not to mention all the messed up keyboards I need to order some conductive paint for.

 

I think the most significant luma line is probably more prone to burning out that buffer since it has to drive the most current. I guess after years and years, they can burn out.

[+DrVenkman]

No problem, like I said, I had the same problem on my 600XL. I think I never ordered the replacement though I have lots of stuff with bad chips in it that I just don't have replacements for, like the bad FREDDIE in my 65XE, there's a bad 4050 in one of them, bad delay line in the same one, some bad DRAMs on my 400's 48K card, not to mention all the messed up keyboards I need to order some conductive paint for.

 

I think the most significant luma line is probably more prone to burning out that buffer since it has to drive the most current. I guess after years and years, they can burn out.

 

You're probably right - in the last few weeks I've power cycled this particular 800XL more, over a shorter period of time, than probably at any point since it was new in the 80's - I've been using this machine to rest RespeQt builds and compare boot performance with RespeQt to the same .atr files using SIO2OSX. That 4050 is also suspiciously close to the power line video circuit jumper that's installed as part of the 800XL Quick and Easy Video Upgrade I performed on it a month or two ago. Perhaps I was careless with the iron and got the chip or board too hot right nearby, or hell, it may just have died.

 

In any case, the machine is working great again, and I didn't have to turn any more working machines into donors, so thanks!

[+DrVenkman]

No problem, like I said, I had the same problem on my 600XL. I think I never ordered the replacement though I have lots of stuff with bad chips in it that I just don't have replacements for, like the bad FREDDIE in my 65XE, there's a bad 4050 in one of them, bad delay line in the same one, some bad DRAMs on my 400's 48K card, not to mention all the messed up keyboards I need to order some conductive paint for.

 

I think the most significant luma line is probably more prone to burning out that buffer since it has to drive the most current. I guess after years and years, they can burn out.

 

So here's an interesting Afterward to this story from a week or so ago ... after I installed that replacement 4050 hex buffer chip, things have been great until today. Following a couple days' wasted effort trying to get my new U1MB working in one of my 1200XL's, I gave up on that temporarily and installed the U1MB in this 800XL. Booted right up and was fine for about 15 minutes. Then I started having yellow screens on boot. Powering down for a count of 5 - 10 seconds would sometimes bring it back to life, but as soon as I tried a cartridge game as a test, all I got was black screen boots.

 

When I opened the case, I discovered that the top of C50 cap right next door had popped splooged around the top of the cap. Go figure, the first cap I've ever had fail on a vintage computer. So I pulled the cap, cleaned out the holes, put it back together and put it into storage. I'll have to find a replacement eventually. Guess I can add a few of these to that "eventually" order from Jameco, lol.

 

I then pulled my spare 800XL from storage, yanked that horrendous C56 "blurring capacitor" out of the RF circuit, then installed the U1MB in that one. Works great. Whew.

[+DrVenkman]

 

When I opened the case, I discovered that the top of C50 cap right next door had popped splooged around the top of the cap. Go figure, the first cap I've ever had fail on a vintage computer. So I pulled the cap, cleaned out the holes, put it back together and put it into storage. I'll have to find a replacement eventually.

 

 

I ordered a lot of ten 10 µf capacitors from eBay for $2.38 last week. They arrived yesterday so this morning I replaced the dead cap at C50. The machined powered right up and has been running a burn-in test all day. I've power-cycled it a couple times over the course of the day to test different things without a problem. I'm going to let it run for about 48 hours straight, but I think the patient is gonna live.

[Poochy]

Sorry for the bump, but I had an NTSC 800XL from ebay with the issue from the first post.  Swapped the 4050 with one from a PAL 600XL (with U1MB installed) and the 800XL is all good. 
However, put the dodgy 4050 in the 600XL, and it's all good there too!

Using contact cleaner and swapping the chips over a few times consistently brought the same results: both were good in the PAL 600Xl, only one worked correctly in the 800XL.

Should I be expecting different faults in the 600XL to appear with dodgy 4050?  (I've ordered a couple anyway).