HELP trying to get my atari 720 degrees to work - losing my mind.. any advice?

720fan

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HELP trying to get my atari 720 degrees to work - losing my mind.. any advice?

Hi all, i have a 720 machine that stopped working on me a while back and recently i decided to fix it. i have tried the machine with 2 different boardsets (cpu, and video boards) and 1 additional video board...
what happens: all the lightbulbs on the cabinet light up, the speakers hum lightly (like they are getting power) the monitor flashes white for a split second when i power on and power off the machine, both cpu and video boards light up red. there is NO game audio and no picture at all.
i have measured the +5 on the boards, when i adjust it to 5.0 on the video board it reads at about 5.3 on the cpu board, when i adjust it to read 5.0 on the cpu it goes to about 4.7 on the video board...can anyone that has a working one tell me the measurements they are getting?

something i noticed... the brown/white and red/white wires coming off the original 5 volt supply(long replaced) have been cut....in the schematics these go to the video board as "+sense" and "-sense" I thought about replacing these on the wiring but where do they come off of my newer power supply and what should they read? how do i test that they are putting out whatever they should correct? do these even matter? i had it working before since this has been done and did not even notice until i started checking every connector since the new set of boards i got did the same thing...

i do not believe this to be a monitor issue because i do not hear any sound whatsoever when the boards are powered... could my monitor and audio all go bad at once? is there an easy way to test either without a whole new monitor or audio board?

i have attached pictures of the monitor when the machine is powered on, i got it to get bright after i adjusted the "screen" control on the monitor...i do not hear audio at all though, just a light hum.... seeing this, is there any chance it is a monitor issue still?

i am not an expert and any help is greatly appreciated. thanks for reading.
joe
 

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If all alse fails, send your boards to El Dorado and swap them for a tested and working set for like $135. Then if that doesn't fix it, send your monitor board to Chad at arcadecup.com.
 
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