Dead 800XL - help requested

[Grand_National]

Hi.  New to the forums.  So, back in the day, my father and I both used Atari 8-bits as our first home computers.  It actually was my computer in college.  Fast forward....I thought it would be "cool" to show my son what it was like back in the "old days" of computers.  I wanted to hook one up to a modern TV, so I planned to use composite out on my Dad's 800XL after my mom had given it to me several years agao.  After finding a 5 pin and some RCAs, I thought I was ready to go.  I plugged in the power supply ready to start working on the composite out connectors, turned it on, but NOTHING happened.  No red power LED, absolutely nothing happened when I flipped the switch.  I've checked the pins on the 7 pin DIN and the power supply is still putting out 5-5.10 volts.  I should mention I have a CO61982 power supply (rectangle, white top, black/brown bottom), not an ingot PS.  I opened up the case (dated inside Jan 27, 1984) and tested a few places with my multi-meter and the board has 5 volts.  I wasn't expecting this issue with it doing absolutely nothing.  The question now is, what to do next?  Are there common issues with these old machines which I should look in to?  After opening it up, I looked for bloated capacitors, or anything generally discolored or melted, etc., but nothing stood out.  The only thing I noticed was the keyboard ribbon where it connects into the edge connector on one side seems a bit, well, "fried", such as corroded.  The keyboard ribbon cable traces themselves also look discolored at both ends; where it goes into the edge connector on the motherboard and also where it goes into the keyboard, sort of like "blackened" like they took too much voltage.  I can't ask my father if when it stopped using it, it had actually died or he had just moved to a PC since he is no longer around.  I'm looking for some ideas on how to test this box to hopefully bring it back to life.  Ideas?  Tips?  All feedback is welcome.  Thanks in advance.

[CapitanClassic]

Never had to troubleshoot a 800XL yet, but the first thing to check is documention in the Field Service Manual. Unfortunately when I was reading the Atari 2600 FSM, one of the first things to check after the voltage regulator is the TIA and RIOT chips, which I don’t have spares of. I ended up having to buy a second 2600.

 

https://archive.org/details/Atari_800XL_Field_Service_Manual/page/n1/mode/2up