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New to me Atari 800


random_rodder

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If you've measured 5v at the DRAMs with the other PSU then that's a good sign.

 

It sounds like from your description that the CPU is good but may be getting lost and is crashing due to bad rom, bad stack ram or some other logic fault.

 

Does the computer appear to do something when you press the reset button ?

 

What happens if you hold the option key whilst turning the machine on ? Does that bring you into the test mode ?

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I just looked at the gut shot above and it appears your OS rom was replaced at some point. There's an EPROM (The chip with the glass window ) there instead of the original chip. What are the markings on that chip?

 

So I would definitely suspect that repair and get someone to verify the OS rom and basic rom whilst they are at it.

 

You can also get an original OS rom from Arcade components. He is great to deal with.

 

http://www.arcadecomponents.com/catalog/item/3054735/5262650.htm

Edited by shoestring
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Does the computer appear to do something when you press the reset button?

 

Nothing discernible.


 

 

What happens if you hold the option key whilst turning the machine on? Does that bring you into the test mode?

 

Slightly longer hang on a full orange screen (probably less than a full second, but plainly visible), then to black.

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I just looked at the gut shot above and it appears your OS rom was replaced at some point. There's an EPROM (The chip with the glass window ) there instead of the original chip. What are the markings on that chip?

 

So I would definitely suspect that repair and get someone to verify the OS rom and basic rom whilst they are at it.

 

You can also get an original OS rom from Arcade components. He is great to deal with.

 

http://www.arcadecomponents.com/catalog/item/3054735/5262650.htm

 

This is the chip that had a sticker on it with the manufacturing information. The sticker became detached long ago - it fell out when I opened up the computer. At that time I didn't realize what it was and I've misplaced it... so I can't tell you much about it.

 

Which one is the OS ROM and which the BASIC?

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Any closeup of that EPROM ?

 

Don't have a closeup for you right now, but I did locate the sticker which I believe was on the chip that fell off. it says:

 

A stylized logo that appears to make the letters cdy (it's the "c" at the beginning I am not 100% on - it's definitely a "d" and a "y")

 

"Omniview"

 

XL/XE

 

by

 

David Young

 

And I just realized that... duh... "dy" must stand for "David Young." Not sure if the thing around the dy is supposed to be a "c" or not. From another thread on the board, looks like that was a replacement OS:

 

 

 

 

 

omnimon was a replacement OS, with ML monitor built in, very useful...

 

Is this the likely culprit? How would I go about getting a replacement for this chip... not necessarily another of these custom chips, but whatever chip was originally supposed to be there?

Edited by mozartpc27
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The OS ROM is 28 pin, and BASIC is 24 pin.

 

Well, on the one hand, the 28 pin OS ROM is the one that appears to be a "custom" replacement. It is the "Omniview" XL/XE by David Young, and looking at the chip more closely, it has the following information on it: N JAPAN 8505 00009SS0 HN4827128G-25.

 

On the other hand, the ROM chip is among the chips I measured receiving 5V. I guess I still need to re-measure after looking at the schematic, but still.

 

A refresher of what I have looked at in terms of the three chips above the right most chip along the bottom row (the picture is on the previous page):

 

 

Moving upward one at a time from the last chip in that bottom row (C014795-12):

 

AMI 8328BLE C0122948-01 C03051 Korea: Ground test lead positioned bottom left, positive test lead positioned top right: 5V

 

Omniview XL/XE by David Young, N JAPAN 8505 00009SS0 HN4827128G-25: Ground test lead positioned bottom right, positive test lead positioned top left (OS ROM): 5V

 

NCR2364-30 F807612 N8326 C060302A-29 © 1979 Atari: Ground test lead positioned bottom right, positive test lead positioned top left (BASIC ROM): 5V

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That gives you a software based 80 column screen. Use a good monitor, preferably monochrome for this. It is very difficult to read on a cheap TV.

 

Cool, thanks. I have a Commodore monitor with a chroma / composite hook up. Can't get the Atari to output to that either - I assume this eliminates an issue strictly with the RF output itself (and perhaps with the CTIA chip?). Based on another thread, I ordered a copy of Star Raiders - apparently this cart has a diagnostic component to it and, if it boots, will eliminate certain chips as the cause (CPU/ANTIC/GTIA). See this thread - http://atariage.com/forums/topic/177258-atari-800xl-nothing-on-screen/

 

Otherwise, looks like I might need a "parts" 800XL. Not sure when I will be able to pick one up for that.

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You should at least verify the contents of the EPROM, get it re-programmed if it doesn't check out or just get a replacement if you don't have a programmer to do the verification yourself.

 

EPROMs have a tendency to forget their data after 10-15 years or so ( this is called bit rot ).

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It would definitely be a good start since you've already eliminated the power source as the potential problem.

 

You could go ahead and use a shotgun approach but you could potentially waste a lot of money if you don't get lucky.

 

The best and cheapest option may be acquiring a working a8 system and substituting known working parts.

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  • 3 weeks later...
  • 4 weeks later...

Finally just bit the bullet and acquired another, working, Atari 800XL. Got a little bit of a deal - but boy I wonder where this thing was kept, it has all kinds of literal dirt inside it leaking out.

 

It does turn on and boot up. At some point will try switching out chips to see what was fried in the one I had and maybe try to Frankenstein together my "best" available Atari 800XL.

 

So today I tried the disk drive that came with the original 800XL I bought. It's a later model 1050 I think, in a case meant to match the look of the 800XL.

 

I was suspicious of the drive before, as although the power light comes on when you plug it in and turn it on, there was no tell-tale whirring of the drive to let you know it was setting itself for use, and even the manual says the busy light should come on for a moment, but it never does. Today I confirmed, apparently, that the drive does not work. I think I have the device settings done correctly. I think I have it hooked to the computer correctly. But it does nothing when I boot up the computer, then turn it on, or turn it on (as the operating manual recommends), then turn on the computer.

 

But this is where my knowledge fails me: I do not have a copy of the "DOS" the manual refers to. Is this necessary to make the disk drive work at all?

 

Sorry for the questions - but I am new to the Atari 800 experience! I am and have been a Commodore guy.

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There's always the option to do away with disk drives and disks, and go the Atarimax cart route (or other such cart system).

 

This may not be the cheapest option but you should find that it's easy to find access to a whole library of titles.

 

Harvey

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Sorry your first experience was not so good. Both a deal computer and drive. Well if you stick with it, you have parts sources now.. Or once you get into it enough you can get them both working again.

 

There are deals to be had.. and you can get burnt.. thats for sure.

 

James

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I'll throw in with this thread, as I am in a similar boat.

 

I just decided to take a gamble on an "untested" Atari 800XL with disk drive listed on ebay, because the computer was being sold close to my home. Got the computer, a 1050 disk drive, a 301 modem, and an 850 port expander for $74.99 since I was the only one who bid. It seems it was a sucker's bet, however, because I cannot get a picture from the computer.

 

This computer did come with a whole mess of stuff, including two power supplies. So I've tried running the computer through both PSUs, through both an older CRT television with have which works (and which my Coleco ADAM is hooked up to), and through a Commodore 1084 monitor I have using the composite video cable that was included in the package.

 

When I try with the monitor, I just get a black screen with both power supplies.

 

When I try with the TV, one power supply gives me a black screen, the other some reddish tinged feedback - not a picture, but not nothing.

 

Where should I start? I'd also love to know if the disk drive is any good, but with am not sure how to test it if I can't get the computer running.

 

 

Hi Mozart
I had an 800xl hongkong motherboard last week with your exact symptoms, the dim redish feedback screen with rf and black with composite/monitor. I was able to swap some chips from a working machine and found the C014806c-03 was bad. Its the 3rd 40pin ic over at the bottom.
try swapping that chip and see if your machine boots.
Edited by bugs
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  • 3 weeks later...

Well, I finally got around to doing a complete swap-out of every chip from working 800XL into my non-working one (well, not EVERY chip, but the CTIA, ANTIC, Sally, PIA, POKEY, EPROM, and the CO60302A-29, whatever that does). I had also previously replaced all RAM in the non-wiring 800XL. Still nothing. I am guessing the board itself might be fried.

 

So, I cleaned out the other one I bought as best I could, and that is going to be my 800XL going forward. It's ashamed, because the chassis and keyboard on the non-working one are better than the working one, but swapping out wholesale seems like more trouble than its worth, having taken it down as far as I did. Surprised to see with so much socketed that the keyboard appears to be soldered to the board.

 

What's weird is that the non-working 800XL, like I said, is relatively clean, clearly kept in reasonably dry circumstances, etc.

 

Meanwhile, the one that works must have been kept in some kind of outdoor shed, and not a particularly tight one either. All kinds of dirt, pine needles, cob webs, dead bugs, etc. inside when I opened it up. But it works.

 

Anyway, thinking I might put the non-working one up on eBay for parts, unless someone here has an interest.

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