Atari 800 Solid White Screen

[Falter]

As mentioned in another thread, I have an early 800 that powers up to a solid white screen on composite and almost nil on TV.

 

When I first powered it up I recall having this issue. I cleaned the edges of the cards and with a bit of pressure on top managed to get the thing to power up to Memopad, BASIC, etc. I then thought I'd do a bit more cleaning of the ROM socket in particular.. after which it hasn't worked since.

 

When I was initially troubleshooting the first time, I ordered a spare ROM cart and plugged that in. I can no longer remember which cart it worked with, but now neither does.

 

I have a GQ-4x4 EPROM reader and was wondering if maybe I could read the ROMs and make sure they're still alive. I can't think of anything I might have done to damage them, apart from repeated power ups and applying pressure on the card when I was trying to get them to operate.

 

Other options I've considered include picking up a known good 800 motherboard, maybe another ROM cart. I'm pretty sure the RAM is good, I removed and tested with a RAM tester in an Apple II. The CPU card would be he only other unknown.

 

Power voltages seem to be fine. I actually went through with the ROM cart plugged in with my DMM and checked continuity between the top of each pin and where it solders into the motherboard on the other side... all seemed to make the connection (although, you can go crosseyed doing that so who knows if I missed one).

 

I also removed and reseated every single IC in the machine. None of the legs on them them looked dirty or rusty.

 

The CPU is good.. I tested it in a PET.. no problem there.

 

At a loss at this point.

Edited March 10, 2019 by Falter

[+Nezgar]

You definitely should be able to read the ROM's... at least the two main OS ROM's as 2732's.

 

You can compare the output against other known ROM's here: http://www.wudsn.com/productions/atari800/atariromchecker/help/AtariROMChecker.html

 

Other than trying with only 1 of the 16K modules installed at a time, I'm not versed enough in the 800 to help you further, but I recommend posting in the Atari 8-Bit computers forum, there's a lot more people active there to see your post: http://atariage.com/forums/forum/12-atari-8-bit-computers/

 

Good luck!

[CZroe]

Shortly after I got my Atari 800 I was testing someone else’s Atari 800XL and had a possibly-similar problem. I tested with a Pitfall 2 Lost Caverns cart and it worked, then I tested without a cart and it still worked, then I tested with Pitfall 2 again and it just stopped working. One of the pins in the cartridge port bent and shorted to one of the others, which prevented it from working with or without a cartridge.

 

I desoldered it, extracted the pin, straightened it, and switched it with a pin the looked unused. It’s worked perfectly ever since, but I’ll never trust Activision cartridges again! Since this started after cleaning the cart slot I figure it could be something similar.

[ClausB]

Any luck with this? Another trick we use with those tinned card edge connectors is to run an eraser over them to remove the dark corrosion.

 

Looking forward to seeing it on your excellent YT channel.