shawnerz
Experienced Member
Hello all.
I was wondering if any of you can get me looking in the right direction.
I have a 1520. I power it up and it works great - for about 5 minutes. After that, if you press a key, nothing happens (on the screen, at least). After 16 presses, there is an error beep with every key press and nothing appears on the screen.
It stays this way until it is rebooted. When rebooted, it does the same thing: works for about 5 minutes, nothing on screen, then error beeps when keys are pressed.
In my troubleshooting, I wanted to remove as many variables as possible. I removed the modem, all but the minimum 1 MB of RAM, and the hard drive.
But, it still has the same problem.
I have swapped 286's (microprocessors rarely fail in this way. Since it's socketed, I thought I'd try it).
I've swapped (and now socketed) the keyboard controller PROM.
I replaced 2, 100 uF electrolytic caps (1 near the keyboard PROM, and 1 near the 286)
I poked around the controller PROM with an oscilloscope, but I don't know what's a good signal, or what's a bad signal.
Are there any buffer latches that I should check?
I'm open to any ideas.
Thanks,
-Shawn
I was wondering if any of you can get me looking in the right direction.
I have a 1520. I power it up and it works great - for about 5 minutes. After that, if you press a key, nothing happens (on the screen, at least). After 16 presses, there is an error beep with every key press and nothing appears on the screen.
It stays this way until it is rebooted. When rebooted, it does the same thing: works for about 5 minutes, nothing on screen, then error beeps when keys are pressed.
In my troubleshooting, I wanted to remove as many variables as possible. I removed the modem, all but the minimum 1 MB of RAM, and the hard drive.
But, it still has the same problem.
I have swapped 286's (microprocessors rarely fail in this way. Since it's socketed, I thought I'd try it).
I've swapped (and now socketed) the keyboard controller PROM.
I replaced 2, 100 uF electrolytic caps (1 near the keyboard PROM, and 1 near the 286)
I poked around the controller PROM with an oscilloscope, but I don't know what's a good signal, or what's a bad signal.
Are there any buffer latches that I should check?
I'm open to any ideas.
Thanks,
-Shawn
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