Atari 2600 clone (flashing/blue-ish screen)

[Andreashad]

Hello guys! This is my first post and English is not my first language, so please forgive any mistakes.

 

So a few days ago I found this little guy in a storage room filled with broken pcbs and other junk and i decided to try and fix it.

First i noticed that the top part of the power switch was missing so i closed the circuit by putting jumpers on the switch,

then plugged in a 9v adapter and tried hooking it up to a CRT to see if it was working...nothing came up so the first thing i checked was the 7805 regulator which was dead.

I replaced the 7805 and i made a rough RF to AV mod (just video. no sound) from a schematic i found online. I plugged it in (AV) and this time it worked perfectly, even when i connected it through RF,

it had a bunch of built in games on it, it was great! But sadly after 10 minutes or so, the picture went crazy all of a sudden with flashing colors of all kinds of patterns (see attached photos).

Also when i plug it to the RF connector the picture is blue-ish with static and there is a high piched sound in the background.

I really hope i didn't fry it or something, because i wanted to make a case for it and give it to my brother as a birthday present...

Any ideas what's wrong with it, or how to troubleshoot it? I'm not really good on electronics but i know a thing or two...

I also attached the AV mod i i did (not my photo).

 

Thanks in advance!

Edited November 20, 2018 by Andreashad

[Jason_Atari]

Have you checked the electrolytic capacitor near the voltage regulator?

[Andreashad]

Have you checked the electrolytic capacitor near the voltage regulator?

Thanks for your reply! yes i did...i even swapped it with another one (1000uF 35V) but the video output is still the same

[Andreashad]

I should mention that i have a digital oscilloscope and i know how to make basic measurements (really basic ) if that helps.

Edited November 21, 2018 by Andreashad

[+Stephen Moss]

If it is OK when you initially power it up and then goes crazy after 10 minutes, it may be that something is drawing too much current and either failing as it gets hot or overheating the regulator causing it to shut down (check output voltage).

 

If the crazy video is now permanent (occurs as soon as power is applied) and the output from the voltage regulator is OK then something may have died. Nothing in the images looks discoloured, so unless you have some freezer spray you will have to sniff/feel around for anything that seems excessively hot.

[Andreashad]

If the crazy video is now permanent (occurs as soon as power is applied) and the output from the voltage regulator is OK then something may have died. Nothing in the images looks discoloured, so unless you have some freezer spray you will have to sniff/feel around for anything that seems excessively hot.

Unfortunately the crazy video is permanent. The only thing that runs pretty hot is the regulator (7805CV) but it outputs the correct voltage (4.98V), i'll try an find another one just to test it.

[Andreashad]

I changed the regulator again but no luck. One thing i noticed is that all the ICs are pretty 'cold' when the power is on except the one marked 0410 - 8951 (the one on the left above the cartridge slot ) which runs warmer than the others (42 Celcius/ 107.6 Fahrenheit). Anyone knows what is that IC's purpose?