Blue Screen\Black Screen & Sprites

[Awoodbridge]

I have a 400 that I picked up today. It was working great for about an hour.

 

Now if I boot basic/no cart I get a blue screen with keyboard click. The 

 

If I boot PacMan I get a black screen and if I start the game just the sprites. I opened it up and reseated the daughter cards, that didn’t work.

[Sugarland]

24 minutes ago, Awoodbridge said:

I have a 400 that I picked up today. It was working great for about an hour.

 

Now if I boot basic/no cart I get a blue screen with keyboard click. The 

 

If I boot PacMan I get a black screen and if I start the game just the sprites. I opened it up and reseated the daughter cards, that didn’t work.

 

Congrats on your pickup. I would try reseating as many chips as possible and using deoxit. Guessing it's a corrosion on chip legs issue.

 

[Sugarland]

Another possibility is that the power supply overvolted the previously working computer. Check your voltages when powered on.

[Awoodbridge]

Reseating all the chips didn’t work, voltage seems fine. Pokey chip was half out when I went in, but from my understanding is not the issue here. Contact cleaner on the way, there is a lot of oxidation especially on the GTIA.

[+Nezgar]

If any games work, but BASIC doesn't, it may be a bad 2K floating-point math ROM- CO12399B ..

 

But you say even without BASIC doesnt work, so it could be many things. RAM? OS ROM's? Chip swap time with another machine...

[Kyle22]

Do any capacitors look swelled up? The tops of them should be flat, not heaved up.

Replace any that look bad.

This is not too common on 400/800, but it never hurts to look.

 

[Awoodbridge]

As a last ditch effort, I swapped RAM chips ABCDEFGH -> EFGHABCD. Now I'm getting a black screen. Is it worth getting a new RAM card? I don't have a donor machine for swapping chips?

[_The Doctor__]

time for new ram chips or ram card...

[mimo]

tf_hh sells a great 48k upgrade and the SCCC is a must have for 400 owners