Broken Atari 2600 with Black Screen

[+McCallister]

I've got a six switch which powers up, but only displays a black screen with a blue line on the left and an orange line on the right. I've attached a picture below of the screen. There is no sound or anything else, just that screen. Does anyone know what the problem is and if so, is it fixable?

[gameofyou]

I am currently troubleshooting a similar problem on an Atari Jr. After making some measurements, I found that the input to the 5V regulator was low, which made the output low. I traced this back to the Power switch. The switch is faulty/corroded, so that when you switch it on there is still 100 ohms or so of resistance which causes a voltage drop. I am going to try to find a replacement switch and see if that solves all my issues.

[shadow460]

MY first guess is the CPU isn't starting up correctly. That doesn't narrow down the problem much, though.

 

Clean the cartridges and the port first. Next, check the power supply voltage. It should be somewhere above 9 volt but probably not over 13 with no load on it. Once inside the console, I'd try cleaning up the power switch and re seating any socketed ICs. When you pull them out, you can try cleaning the pins with annhydrous alcohol. 70% will not work because it will leave a residue behind. It's fine for cartridges, but not for something you have to open a console to get to, so use annhydrous alcohol for this or maybe some kind of electrical contact cleaner. Once that's done, carefully re seat them.

 

Not to sound cocky here, but that's really about as far as I'd go if you're not comfortable working with electronics.

[+McCallister]

Thanks for all of the information. I tested the power supply, and it is outputting the proper load (also, it works with a different 2600). Next, I tried pulling out the top chip (pics below) and nothing changed when I powered it on. So, I placed that one back in and removed the bottom one. The output changed when it was out and after I placed it back in, the black screen pictured in my first post returned. Would it be safe to assume that this chip is faulty?

 

 

Not to sound cocky here, but that's really about as far as I'd go if you're not comfortable working with electronics.

 

That does not sound cocky at all and no, I am not that comfortable with electronics, so thanks for the advice. I just want to see if I can get it working, or if I should scrap it for parts.

 

Added photo of the board for reference of which chips I am talking about.

[+McCallister]

Another dumb question: what is the bottom chip called?

[Ian Primus]

The bottom chip is the TIA. There are three main chips in the Atari - the RIOT, the CPU, and the TIA (top to bottom). The RIOT contains the system RAM, the interface for the joysticks, and the system timer. The CPU is the main processor, and the TIA handles the graphics.

 

Your problem is one of those annoying ones that's hard to diagnose without a working Atari to swap chips with - the black screen means that something is seriously not right. It could be a dead CPU, or it could be a dead TIA, etc. Normally, you should be able to turn on the Atari with no cartridge and get "humming bars" - vertical colored lines and an annoying tone, that's different every time.

 

Is one of the chips getting abnormally hot? Feel them with your fingers, right in the center while it's on. One chip getting super hot will be a dead giveaway.

 

-Ian

[+McCallister]

Thanks for the clear lesson on chips, Ian. Much appreciated. I will try the heat test and see what I find. Based on what I have done so far, I am tending to think it is the TIA, but will wait until I try the hot test.

[shadow460]

I've had two consoles come in with similar symptoms, and it was the RIOT both times. I'm about 80% sure the RIOT chip is bad in your system. It's the one closest to the cart slot. If the TIA was going bad, you'd still see the game's graphics but there would be problems with the colors. Given that you have 5.18 volts coming from the regulator, I assume that's good. Try resocketing JUST the RIOT chip. If that doesn't work, replace it. Soldering it down might help. I think your only other possibility here is a faulty CPU. Fortunately, both chips can be had on the cheap.

 

I have at least one or two CPUs available, but I don't have any RIOT chips that aren't currently installed.

Edited February 3, 2013 by shadow460

[+McCallister]

Finally found the time to get this working. Turns out it was the CPU! And then it was the voltage regulator, which up until then seemed good, but then the colors went screwy because it was only getting 3 volts. Swapped that out and now it runs great. Just wanted to thank everyone for all of the great advice, without which I would not have been able to get this working.

 

Now, if I can only learn how to solder and desolder better...

[shadow460]

Dead carts are excellent for soldering practice. I just soldered and desoldered a couple of times until I was comfortable with it, then ripped into my 7800 for a successful mod.

 

Just don't so like I did and get halfway through desoldering an IC only to realize it's the wrong one!

Edited March 30, 2013 by shadow460