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800Xl doesn't want to be repaired!


virtvic
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I had a perfectly good, working 800xl until not long ago - I turned it on after not using ti for ages and I just got a black screen.

 

After googling and reading some of what you fine folks on here do to repair 800xls, I replaced all the rams with sockets and new 4164s.

 

NO CHANGE.

 

I recapped the motherboard, just for the sake of removing those tired, old caps

 

NO CHANGE.

 

I socketed the OS chip and burned a replacement - now I geta browny / red screen? I verified my new eprom to the code and also read out the original and verified it to the code and they report as being good (the same code) ???

 

 

I socketed the BASIC chip and left it out to see if the computer booted without it

 

NO CHANGE

 

I bought (yesterday) a working 65XE (nice boxed) and another working 800xl. I swapped over the working main ICs to no avail...

 

I'm now thinking about replacing the 2x 74LS158N ics near the ram, thinking they may not be controlling the RAM properly?

 

I'd really like to persevere and get this old boy going, I've had it a long while and still miffed it just died on me...

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First thing to do after replacing all those components, perhaps needlessly, is get a scope or at least a cheap logic probe and use it plus a multimeter to figure out what’s actually wrong instead of shotgunning and doing lots of potentially more unnecessary work. I brought a 1200XL back from the dead that required three new sockets, a new 6502C and a new GTIA, plus a new controller jack. But I’d never have been able to figure out what was up had I not traced signals on the board and figured out what was actually wrong.

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my 65xe gave me 'the red/brown screen of contempt' but it turned out to only be the MMU so i'd recommend also checking that

 

ive also known bad OS ROM, CPU, freddie or RAM to cause the same. swapping the chip for a known good one is a simple way to check if you can?

 

best of luck

Edited by xrbrevin
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Are you sure the RAM you put in is OK ?

 

Was it mT RAM originally ? If not I wouldn't have suspected the RAM in the first place.

 

If you put in "new" mT RAMs there might be a problem there, i bought NOS mTs that turned out to bel all defective when I was in the arcade hobby.

 

And tired old caps.......I have yet to find a single bad one in an Atari 8 bit machine, and I've measured all of the ones I have come across. Seems Atari used good quality caps (even in the Tramiel years) and there is simply almost no heat inside an A8, which is key for caps to keep healthy.

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And tired old caps.......I have yet to find a single bad one in an Atari 8 bit machine, and I've measured all of the ones I have come across. Seems Atari used good quality caps (even in the Tramiel years) and there is simply almost no heat inside an A8, which is key for caps to keep healthy.

 

I've had exactly one (ONE) capacitor in an A8 go bad on me - it was a tiny little 10 uF radial cap near the 4050 chip in the video circuit of an 800XL. The machine still booted, it just had messed up video. And the failure was visually obvious - the cap had split near the top and electrolyte had leaked out.

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My friend Dr Dean (the videogame whisperer) has just told me I need to use a doubled up image on a 27128 to replace the BASIC IC, which I'll do later on today.

As for the RAM, I replaced it with 4164, not those trash mT ones either - they sound like the equivalent RAM to Fujitsu eproms :mad:

 

I don't really know how to use a logic probe properly (although, I do have one) - otherwise I probably would have this thing working by now. I have ordered the 2 74LS ics that control the ram, so will socket and replace them when they arrive. I will also make up an eprom converter and reburn the BASIC chip too. Even if this is shotgunning, it will hopefully make the computer a bit more 'future proof' anyway. It's not like the chips are very expensive anyway...

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No, most XL/XE supplies are fine as long as you don't have the Ingot.

 

Warning, the part numbers are the same on different models. See pic. Thanx to original source of pic.

post-13040-0-25669500-1530582807_thumb.jpg

 

The RED X one will go over voltage and take out your computer! RAM chips are especially vulnerable.

 

If you have an ingot, get a good one now! Cut off the (Atari side) cord and connect to a GOOD 5V supply capable of 2A or better. Observe POLARITY!

 

Hope this helps. Best & B&C should have good (NON Ingot) Atari supplies in stock as well.

 

 

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I had a 'new old stock' silver label go bad on me last year. It didn't fry the computer but it did make the computer behave very strangely. I cut the computer side of the cord off and threw it away before it _would_ cause damage. I would not recommend a silver label (shown above) even though there is a prominent Atari vendor saying they are reliable who incidentally happened to sell them.

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