Need help with my old 1200xl

[8bitold]

Hello everyone,

    Long time lurker, first time poster. I recently got back into the Atari scene and bought a 130xe of fleabay and it works gloriously. So I pulled out my old 1200xl, connected it to the AV2HDMI and get a blank green screen. It is acting like it is not even loading. The AV cable/adapter/monitor works on the 130xe and my TI99/4A so I know the cable is good. I attempted at adjust the color with R48 adjustment on the board hoping that I could see the self test or the notepad. The colors shift change so I know I am getting a video signal from the unit.

   When I was a kid I bought a 1200xl keyboard from Radio Shack and found one of the IC had some sort of sync issue. The video image was shifted. If a certain IC was tapped with a finger it would shift to the center of the screen, and would stay centered for months. When it shifted back I would open it up hook up my keyboard and tap on the IC and low and behold it would shift back. Of course that was 35 years ago and I don't remember which IC it was. I assume this has finally bit the dust and it needs to be replaced. The question is which IC it might be and can I get a replacement.

 

Thank you to everyone.      

[ACML]

I would start with "gently" pulling out and re-seating the GTIA and ANTIC ICs (they are 40 pin VLSI chips).  Those are your video display chips.  If that doesn't change anything, next in a sequence, try re-seating the CPU, ROM and RAM chips. Test system power up after each chip type.  The theory is that the contacts are just oxidized and no longer making good contact.  

 

[_The Doctor__]

push then pull, the sockets are easily damaged....

[+DrVenkman]

If you're getting a green screen, ANTIC and GTIA are working to produce a stable video signal. The issue is almost certainly elsewhere. I'd suggest re-seating the CPU, the OS ROMs and the MMU and trying again. If that doesn't work, then re-seat POKEY and PIA as well. 

 

If *THAT* doesn't work, there are any number of things than can prevent or interfere with the boot process, so try these steps first. 

[8bitold]

1 hour ago, ACML said:

I would start with "gently" pulling out and re-seating the GTIA and ANTIC ICs (they are 40 pin VLSI chips).  Those are your video display chips.  If that doesn't change anything, next in a sequence, try re-seating the CPU, ROM and RAM chips. Test system power up after each chip type.  The theory is that the contacts are just oxidized and no longer making good contact.  

 

 

Thank you. They are oxidized. They did not want to release from the sockets. I pulled the GTIA, ANTIC, CPU, RAM and ROM. Same results after each.

 

16 minutes ago, DrVenkman said:

If you're getting a green screen, ANTIC and GTIA are working to produce a stable video signal. The issue is almost certainly elsewhere. I'd suggest re-seating the CPU, the OS ROMs and the MMU and trying again. If that doesn't work, then re-seat POKEY and PIA as well. 

 

If *THAT* doesn't work, there are any number of things than can prevent or interfere with the boot process, so try these steps first. 

Thank you. I pulled the MMU, POKEY and PIA and now it is still green with colors at the top of the screen. 

 

I will pull what I can a reseat the rest.

 

 

[8bitold]

Here is what i see. Thank you.

[+Roydea6]

It might just need a burn in time.  After pushing and pulling on the IC's leave it turned (maybe without the Monitor(TV) turned on for 4 to 8 hours.  The capacitors and resistors loose efficiency after a long storage time.  The keyboard is the crankiest and may need more repair...

 

Edited May 11, 2020 by Roydea6
miss spelled may

[8bitold]

1 hour ago, Roydea6 said:

It might just need a burn in time.  After pushing and pulling on the IC's leave it turned (maybe without the Monitor(TV) turned on for 4 to 8 hours.  The capacitors and resistors loose efficiency after a long storage time.  The keyboard is the crankiest and may need more repair...

 

Thank you. I will try that. The keyboard I am using has barely been used.

 

I was hoping to make this one my mod atari and keep the 130xe original. 

[+bob1200xl]

Where are you located? You could use a chip caddy, try each IC, one at a time.

 

Shipping things around the country is expensive, though, and, as Roydea6 said : the keyboard is probably dead, also.

[_The Doctor__]

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re-seating involved cleaning (deoxit) the pins and socket then re inserting the chips...

 

Edited May 12, 2020 by _The Doctor__

[8bitold]

3 hours ago, bob1200xl said:

Where are you located? You could use a chip caddy, try each IC, one at a time.

 

Shipping things around the country is expensive, though, and, as Roydea6 said : the keyboard is probably dead, also.

Illinois. Thank you.

 

2 hours ago, _The Doctor__ said:

•  

re-seating involved cleaning (deoxit) the pins and socket then re inserting the chips...

 

I will have to look into that process. Thank you.

[8bitold]

Could my old power supply also be he issue?

[+DrVenkman]

41 minutes ago, 8bitold said:

Could my old power supply also be he issue?

It’s just a 9VAC transformer. The Atari 9VAC PSUs are very reliable - I’ve got over a dozen of them around here and they’re all fine. If you have a multimeter, it should read about 10.5 - 11.5VAC without a load on it. Inside the 1200XL, there’s a rectifier and a pair of 7805 regulators to produce the 5VDC needed inside the computer.  

[8bitold]

45 minutes ago, DrVenkman said:

It’s just a 9VAC transformer. The Atari 9VAC PSUs are very reliable - I’ve got over a dozen of them around here and they’re all fine. If you have a multimeter, it should read about 10.5 - 11.5VAC without a load on it. Inside the 1200XL, there’s a rectifier and a pair of 7805 regulators to produce the 5VDC needed inside the computer.  

Thanks. That makes sense. I was planning on checking, just had not got to it yet. 

[+bob1200xl]

I could send you a working motherboard that you could use to fix your m/b.

 

Or, you could just put the new m/b in your 1200XL and keep the old one for spares, hang it on the wall, or send it back to me. It's just so expensive to ship these things around...

 

I have brand new, old stock keyboards, all of which fail. A new mylar from Best is $40.

 

Bob

[8bitold]

bob1200xl - I will message you.

[8bitold]

BTW Bob you are awesome!!!

 

Thank you. 

 

Actually all you guys are awesome.