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added initial wyse 60 repair

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saji 2025-05-02 21:31:07 -05:00
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content/blog/wy-60-repairs/wy-60-repairs.md
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@ -100,19 +100,44 @@ Uh, guys?
Image of more cold joints on a different chip.
It can't possibly be this, right? U17 and U15 are part of character storage, and
I did see the font RAM output non-zero, meaning it had to have rendered
It can't possibly be this, right? U17 and U15 are part of character storage,
and I did see the font RAM output non-zero, meaning it had to have rendered
something! I quickly cleaned up the joints and powered it on. I couldn't see it
at first, but it worked. This highlights the two styles of troubleshooting:
at first, but it worked.
# Takeaway
This highlights the two styles of troubleshooting:
1. Hypothesis -> Solution
2. Hypothesis -> Validate -> Solution
It feels pretty good to zero-shot a repair or fix, but it also can leave you with blind spots.
In my case, I didn't want to try to probe the board while hot, but later it became necessary unless
I just started replacing chips indiscriminately. Once I started probing, I wanted to find something that
seemed "off" before going further. I would have noticed the character RAM eventually, if I finished my
testing of the Attribute RAM. In this case it was easy to spot visually and so I didn't need to test it
any further.
It feels pretty good to zero-shot a repair or fix, but it also can leave you
with blind spots. In my case, I didn't want to try to probe the board while
hot, but later it became necessary unless I just started replacing chips
indiscriminately. Once I started probing, I wanted to find something that
seemed "off" before going further. I would have noticed the character RAM
eventually, if I finished my testing of the Attribute RAM. In this case it was
easy to spot visually and so I didn't need to test it any further.
While I was working on this, my friend was using his unit to develop a USB
keyboard adapter. His unit was slightly more yellow and has some centering
issues, but otherwise is fully functional. By the time I had mine figured out,
the firmware was mostly complete, so it was a quick flash away. I might blog
about it some time, but the protocol is really simple.
I'm typing this last portion in Vim on the terminal, using the VT100 mode.
( image of editing this post with the terminal )
# Next
It's not perfect. I don't know much about ye olde terminal behaviors
and finding replacements for modern tools that weren't built
with a VT100 compatible in mind is a task of itself. The flow control seems
to be DTR-based, which Linux doesn't support natively. We might be able
to hack around that with a shim but that's a problem for later. It works
fine at 9600 baud using software flow control.
To the folks who rave about the terminals of yore, I get it now.