Author Topic: Atari 130XE intermiddently-completly dead  (Read 199 times)

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Offline ELS122

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Atari 130XE intermiddently-completly dead
« on: April 14, 2021, 03:28:19 pm »
I had the power supply fail (0V output) for my Pal 130XE, then I changed to a SMPS which is rated for 2 amps, it didn't work. then I realized that the pinout I found online was the female side not male side as noted, so I had the polarity reversed.
I quickly turned it off (well after I found out that the polarity is backwards) and corrected the mistake.
The power rail was only -1.3 volts when it was connected backwards, guessing that capacitors may've loaded down the power supply enough to trigger the overcurrent protection.

then it seemed like it worked, connected it to a TV, it showed 'ready' and seemed like it worked... but the video was distorted.
The video distortion could be because of the modern TV it was connected to.

I then turned it off, turned it on later again and it was completly dead, no video, no audio, no activity whatsoever, then the next morning it worked again, I confirmed that everything works and it did. then after around 10 minutes it just died again, I then thought maybe because I had the polarity backwards for some time, perhaps the "main" filter cap was damaged and that caused some instability... I changed that, and still completly dead.

I left it on for like 10 minutes and checked which IC's were hot (with a precise finger-sense method  ;D )

in a scale from 0 - can't feel any heat, to 10 - whoah that's cookin
FREDDIE - 0/10
POKEY - 1/10
PIA - 2/10
BASIC  - 3/10
MMU - 3/10
OS ROM - 3.5/10
ANTIC - 4/10
GTIA - 5/10
RAM  - every chip was like 5/10 warm
CPU - 8/10 barely able to leave my finger on it

The TV says there's signal but the screen is completely black, no audio from the keys, there's audio from the program recorder but I'm guessing it's just directly connected to the monitor port.
I have no way of connecting to the coaxial... RF? jack. I use the composite out on the monitor port

the CPU getting hot worries me, but if it sometimes works fine then idk... maybe it's some bad solder joint? I glanced at the solder joints and saw no really broken solder joints, but all looked pretty bad.

I've tried banging it around and nothing changes, well it did the first time I did it but it could've just been a coincidence.

I have no way of desoldering any IC's, nor parts for it... I really hope it's something simple but seems unlikely.
no stores near me have logic probes, I might make one myself with just a couple LED's and a BJT... wont have a Pulse LED but if both LED's are slightly on I'll guess that it's pulsing  :D

oh btw the atari is a PAL one, if that helps.

Offline ELS122

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Re: Atari 130XE intermiddently-completly dead
« Reply #1 on: April 14, 2021, 03:47:34 pm »
I also confirmed that the power supply is at ~5 Volts, it drops to around 4.9 when it's on, maybe it's slightly too low?

I also noticed that it differs from any picture I find of the board, there's a 151 ohm (not a 150, a 4 stripe 1510) resistor going from the GTIA hook up wire to an inductor (I think) beside it. I'll try disconnecting that temporarily to see if it helps, even tho it has been there as long as I remember and it worked fine before.

Offline EHT

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Re: Atari 130XE intermiddently-completly dead
« Reply #2 on: April 14, 2021, 09:31:00 pm »
I'll try disconnecting that temporarily to see if it helps
Not sure what your hypothesis is here. I suggest leave it alone.

From your description, you've damaged a number of the ICs by reversing the power. I suggest you replace the CPU (a standard 6502 I believe?) and go from there. Make sure you have the power connected correctly before you fire it up again and i'd suggest adding a fuse. I'm afraid if you've blown any of the ASICs it may have to go into a glass cabinet in a computer museum...

Offline BrokenYugo

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Re: Atari 130XE intermiddently-completly dead
« Reply #3 on: April 18, 2021, 03:12:00 am »
The ASICs may be available from, they're not the easiest to deal with but if old Atari parts exist in stock somewhere it's there.

That said I regrettably agree with EHT, you're going to need to learn to desolder chips with whatever level of desoldering equipment you can afford. Practice on a junk board, it takes some skill to not destroy the chip, board, or both, but you can do it with just desoldering wick, flux, and a decent soldering iron. A logic probe would be good, a suitable oscilloscope even better. Buy some nice sockets.

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