Help identifying mod in Atari 800XLF

[santac89]

A bit of update:

 

I've put the missing components, soldered out the exploded CPU, put a socket and tried the CPU from the working one. Still dead. So I guess something else is going on (as many mentioned 🤣).

One thing that bothers me is that when I measure resistance from GND to any positive line I get 32 Ohms, and if using continuity/diode mode I get a beep (and also a 32 Ohm reading).

 

Next step, removing all ICs and put sockets. Maybe when I get everything out I can find what is causing that behavior on the board, or at least I can rule out which ICs work and which doesn't. Is there any issue with putting ICs from the XLF into an XL to test them out?

 

 

[Beeblebrox]

@santac89 generally you should be taking ics from the xlf and putting them in a working 800XL to test individually, rather than putting new/working ics in the xlf. Just in case the dodgy xlf is damaging the new ics in the process.

 

Most of the ics from the xlf will go in a stock 800xl with of course a few exceptions. (Ie you can't test the Freddie chip in a stock 800XL as it doesn't use one. Also stock 800XLs have delay line chips, xlf's don't as the Freddie replaced some of the delay line and other logic chip functions I believe. (Correct me if I am wrong about the logic ics people)

 

Trick is with these things to avoid testing too many things at once. One thing at a time ideally. IMHO starting with the 40pin ics take one chip out at a time and test it in the working 800XL.  I'd avoid socketing everything at once. 

 

As has been said with this particular xlf there may well be multiple things wrong to work through. Been there and it can take a long time to get to the bottom of them all. 

 

Are you outputting to composite BTW? If using svideo be aware you'll only get a black and white image on a stock 800XL as chroma wasn't hooked up in the factory bitd.  No issues with xlf's in that respect. 

Edited December 15, 2022 by Beeblebrox

[santac89]

Yes that is what i’m thinking to do. I only tested the CPU in the XLF to see if it was only that one. But now my plan is to test the XLF ICs in the XL. 

 

I’ll post the results once done, right now i’m de soldering each IC. 

 

I’m using composite out btw.

[Vyvyan B.]

You're taking good working parts from a good working machine and sticking them into a damaged board that has a short in it somewhere???? 🤯

[santac89]

So, I tried every IC from the XLF into the working XL, replacing one, testing, put back the original, replacing one, testing, and so on. And it seems that all the 7 ICs are dead 🤕. Some give a brown screen, one a black screen, one no signal at all and one some kind of static. I guess the only thing to do with this board is saving it for parts if I eventually need some passive component or connector. (btw, the short was gone after removing all. It's something I guess 😆)

 

 

Edited December 15, 2022 by santac89

[Beeblebrox]

3 hours ago, santac89 said:

So, I tried every IC from the XLF into the working XL, replacing one, testing, put back the original, replacing one, testing, and so on. And it seems that all the 7 ICs are dead 🤕. Some give a brown screen, one a black screen, one no signal at all and one some kind of static. I guess the only thing to do with this board is saving it for parts if I eventually need some passive component or connector. (btw, the short was gone after removing all. It's something I guess 😆)

 

 

Unfortunate. And when all the good 800XL's ics are popped back in that machine it is working again? (Just to double check):) 

 

 

Edited December 15, 2022 by Beeblebrox

[santac89]

Yes, no problem there. Just unlucky I guess 😑

[Beeblebrox]

5 minutes ago, santac89 said:

Yes, no problem there. Just unlucky I guess 😑

sure. Glad the stock 800XL is running ok. So are you running it on composite to a modern LCD TV?  If you wanna hook it up for S-video (much better output), I can link you to the simple Chroma hook up instructions, plus a tweak I do all the time to remove jailbars from S-video outputs whilst using modern LCD displays.

 

 

Edited December 15, 2022 by Beeblebrox

[santac89]

For now I'm running on composite on a modern one. But I have an old Sony Trinitron CRT back at my apartment in Berlin so I think that for now I will stick with composite. If I can get another one running my plan was to mod it to RGB, I was checking the Sophia 2 mod, have you tried it?

 

Thanks for all the help btw! 

[Beeblebrox]

1 hour ago, santac89 said:

For now I'm running on composite on a modern one. But I have an old Sony Trinitron CRT back at my apartment in Berlin so I think that for now I will stick with composite. If I can get another one running my plan was to mod it to RGB, I was checking the Sophia 2 mod, have you tried it?

 

Thanks for all the help btw! 

Hiya. No worries. 

 

Sophia 2 is amazing and I am lucky to have one. Owing to the global chip shortage crisis you won't be able to source a new Sophia 2 anytime soon. There is a massive waiting list here on AA and it is looking like 2024 before were are likely to see Simius (it's creator) able to source the chip needed to start creating new batches.

 

I'd heartily recommend vbxe, (for XE and XL atari 8bits),which will not only give you rgb but also 80 column text as an option and new graphics modes, colors, blitter modes, etc. 

 

 

 

Edited December 15, 2022 by Beeblebrox

[santac89]

Thanks for the tip, I will check it. 

[mutterminder]

On 12/14/2022 at 7:24 PM, santac89 said:

So, I tried every IC from the XLF into the working XL, replacing one, testing, put back the original, replacing one, testing, and so on. And it seems that all the 7 ICs are dead 🤕. Some give a brown screen, one a black screen, one no signal at all and one some kind of static. I guess the only thing to do with this board is saving it for parts if I eventually need some passive component or connector. (btw, the short was gone after removing all. It's something I guess 😆)

 

 

Sounds like it was hooked up to one of the power bricks of doom.