Atari 800XLF with bad RAM and video issue

[@grahamrolle3923]

Hi Jon Just thought I'd mention that the system clock oscillator has it's input to the LS74 that you replaced, i.e. pin 37 of freddie going to Pin 3 on the 74LS74 Once again a grat video, be nice to see you working on a 16 Bit's at some poinr, so hope you get some work on these soon. (I checked the diagrams Jerzy Sobolo produced, so hope that's correct)

[@flashjazzcat]

Yes you're quite right Graham. So if FREDDIE was suffering from power fluctuations, I guess it could adversely affect the colour carrier frequency. Looks like 5V to FREDDIE is solid on this board, though (I showed Jurgen a trace on the scope and he agrees it's all good). :)

[@flashjazzcat]

Got an STE coming in for a recap next week, BTW. :)

[@grahamrolle3923]

@@flashjazzcat That will be interesting to see :)

[@vintagetechshack]

Your videos are top notch. I've learned a lot from them. I appreciate your hard work in creating these videos and please keep them coming.

[@32bits-of-a-bus59]

Thanks for another video! Your vids are so soothing, the music, camera, the way you are explaining things, and of course the happy ending.

[@flashjazzcat]

Glad you enjoy them. :)

[@michaelstoliker971]

This is the first XLF board that I've ever seen. Thanks for the repair video. I need to review your 1200XL keyboard repair video as I have two 1200XL's with dead keyboards.

[@flashjazzcat]

XLFs have cropped up a few times on the channel - almost invariably in the context of stability problems and how to overcome them. :)

[@GadgetUK164]

I really enjoyed that repair =D Great job! LOL'd @ the "get yourself a Candle" 🤣

[@flashjazzcat]

They are very handy. :) Thanks!

[@przemekkobel4874]

Thanks for the vid. Personally, I'd start with the caps, since if you have bad power, all bets are off (memory tests too). I remember that every service manual from Atari started with checking supply voltage. Number two on their list was testing clock signals. (edit: BTW, you can test the voltage quality with the scope - just use slow time basis, and zoom around 5V level)

[@flashjazzcat]

Micron DRAMs always fail, so it was a no-brainer to fix the RAM before replacing the bulging caps. First thing I did with this board was test for fluctuations on the 5V supply to FREDDIE, since we are forewarned (thanks to tf_hh) about the routing error on the board which can result in really terrible problems with power to that chip. It appears to be absolutely fine on this board, though, possibly because of L3 being replaced by a zero ohm resistor. Nevertheless, I may still add the bypass cap regardless. I also tested voltage to 74LS74 and GTIA before I finally decided the 74LS part was toast. The scope is definitely a real Godsend for this stuff, as you rightly point out.

[@fragalot]

what what WHAT? An XL with a FREDDIE CHIP??? what next an 800 with a GITA chip?

[@cbmeeks]

Great video. What temp is your hot air set to?

[@flashjazzcat]

Thank you. Hot air is set to 400 degrees all the time. I control the temperature with distance. I have the iron at 450 for everything as well. I find it's actually harder to damage things by going in hot and fast than by lingering on jobs through lack of heat. :)

[@cbmeeks]

@@flashjazzcat Makes sense to me. Thanks!

[@A31Chris]

Hi! Over here in the states where can I buy replacement/backup ram for my 600XL? What type etc?

[@flashjazzcat]

41416 ICs are readily available on eBay, but you might want to buy a pair of 41464s and do this simple 64K mod: kzbin.info/www/bejne/bmW7qKKjoNh1asU

[@A31Chris]

@@flashjazzcat Thank you

[@A31Chris]

@@flashjazzcat thanks though my 600XL is already modded for 64k thanks to the late kjmann on AA these are interesting to watch. My issue is trying to run Atari Planetarium. The two SD copies in circulation crash/freeze at diff points on my system. Possible I have defective memory chip. Suspect upper 16k if so since Atari Planetarium is the only program that I consistently have problems with. And system passes built in memory test.