Dead 130xe troubleshooting

[sideburn]

Hello,

 

I've got a 130xe that fried from a PSU overvoltage.

Two RAM chips are getting really hot so I pulled them out.

The main CPU is hot to the touch and I get no clock signal when I put the logic prone on it.

When I pull the CPU from the socket I then do get a clock signal going to it so I'm pretty sure the CPU is also fried.

 

What I'd like to know is if I should see any data signals off the ANTIC or other chips while the CPU is removed. I know the ANTIC is also a CPU but when I touch the logic probe to it, all I'm getting is a pulsing clock signal to one of the pins all the rest of the pins are either high or low. Same goes for the GTIA. I get a clock to it (when main CPU is removed) but nothing else.

 

I'm just trying to sort out if it's probably just the CPU and two ram chips that went bad.

 

Thanks for any tips.

 

Tavis

[+DrVenkman]

Without a 6502 and functioning OS roms, ANTIC has no display list data to process and send to GTIA to display on-screen. So without a functioning CPU, I don't think you should see anything except +5V and a clock signal on the rest of the main chips.

[shoestring]

Sounds like the CPU is shorted internally and that's dragging the +5v down so much that the clock generator isn't working. Are you getting the typical low->high reset signal on pin 36 of the antic or rst pin of the 6502 ? That will tell you if the reset circuit is good or not. The Freddie chip is CMOS and I believe the MMU is as well, probably fried also.

 

This is going to be hard to trouble shoot without a good known CPU.

 

I have a 65xe with a 130xe motherboard that suffered exactly the same fate. I ended up replacing the CPU, Freddie, MMU ( I programmed a GAL16v8 in its place ) , RAM and the GTIA ( I was missing keyboard click sounds ) to get it working again. I also had to replace the OS ROM as well due to my own stupidity.

[Paul Westphal]

Replace ram and main IC's with sockets, grab a ultimate 1mb..

[sideburn]

Shoestring,

 

No pulse off pin 36. Only the 0o clock pin.

[Rybags]

Overvoltage, I would guess the damage is extensive.

Antic is more or less autonomous in that it'll still send the commands like HSync and VSync to GTIA without CPU intervention.

But the CPU derives the Phase 0 signal, unsure if it's vital for Antic's operation.

 

There are some basic video symptoms that can indicate how extensive the problem is...

- mostly solid colour screen but rolling as if V-Hold is off, GTIA probably OK but Antic not.

- steady screen but solid red or brown, occasionally with vertical stripes - Antic and GTIA probably OK but OS not starting = CPU bad, OS bad or memory selection for reading OS Rom bad.

- screen sometimes starts off red or brown then changes to black with no further action - CPU probably good and able to start early OS initilization.

 

 

For such a machine, it's probably easiest to test chips one at a time in a known good test host.

[JamesD]

What condition is the power supply?
It sound like either it is fried or there was a power surge.

[sideburn]

I've ordered ram and a CPU. The screen was black on power up after the disaster.

 

The power supply was an Atari one. 5v 1.5 amp. It was a larger size one.

 

After the fry job, I measured 6 volts off it. I didn't think that would be enough to do any damage. But maybe it was spiking. Soon after it died completely 0 volts but maybe I shorted it out on accident real quick when measuring the voltage.

 

I'm using a home brewed 5.2v 2amp psi now.

[shoestring]

Have a look at the Sam's Computerfacts Technical Service Data - Atari 130XE

 

http://ftp.pigwa.net/stuff/collections/Atari%20documents/Service%20Manuals/Sam's%20Computerfacts%20Technical%20Service%20Data%20-%20Atari%20130XE.pdf

[sideburn]

Thanks!

[+DrVenkman]

The power supply was an Atari one. 5v 1.5 amp. It was a larger size one.

 

 

This is a photo nicked from Bruce from B&C's 'myatari' eBay store. These are the Atari XL power supplies - the one I've got circle-slashed is the "Ingot", known for failures of just the sort you seem to have experienced. If anyone has these, don't use them! Replace them with another more reliable model or simply cut the cords on them for use with a modern 5V power supply.

 

[sideburn]

Yep that's it. I did exactly what you said. Cut the cord and connected a modern 5v supply. Then tossed it. Hate to toss something with an Atari logo on it but oh well...

 

Now I think I know how my first 130xe blew up when I was a kid!

Seems like my earlier 800xl was a better machine. No need for the Atari translator disk to maintain compatability. Nicer keyboard. Better plastic case it seemed more solid. 130xe looks cooler though

Edited June 10, 2017 by sideburn

[BillC]

Yep that's it. I did exactly what you said. Cut the cord and connected a modern 5v supply. Then tossed it. Hate to toss something with an Atari logo on it but oh well...

 

Now I think I know how my first 130xe blew up when I was a kid!

Seems like my earlier 800xl was a better machine. No need for the Atari translator disk to maintain compatability. Nicer keyboard. Better plastic case it seemed more solid. 130xe looks cooler though

A stock 800XL needs a translator disk for early OSB programs, same as the 130XE. It's the 400/800 that don't require a translator disk for these programs.

[sideburn]

Oh yeah, your right. I forgot. I still have my translator floppy disk from when I was 12.