Your guess about it being a tape interface makes sense to me.
One of the quirks of Yahoo is that only the person who posted a photo
and the group moderator are able to see the full size image.
Everyone else has to live with a so-called "screen size" image that's
usually only about 400 pixels wide. You can get around this by
posting your image in the FILES folder rather than the PHOTOS
folder. I've created a folder in FILES called JEROME, and I've put
the full size image there.
Besides doing the checks that Larry discussed, take the time to read
through the message archives about other memory problems. You might
find something useful. Also, check the white wires that run from the
first mother board to the front panel. It's common to have one or
more of them break off where they're soldered. Your computer was
built a little differently than most. Usually, the first mother
board was installed fully to the right side (as viewed from the
front) of the computer. The 2nd, 3rd, and 4th mothers would then be
added to the left of the 1st one. Your builder started in the
middle. There's nothing wrong with that, but it does leave the white
wires a little more vulnerable and messy than would otherwise be the
case. Look at pictures of other 8800s and you'll see what I mean.
You probably already know this, but let me give this warning anyway.
When you're troubleshooting, NEVER pull a board out of the buss with
the computer powered up. You'll most likely cause catastrophic
damage. This has been discussed in the archives too.
--- In email@example.com, "caljer" <caljer@y...>
> Thx Steve. Exactly, window dressing!
> I try to run the small addition program from the manual, but as I
> said in my first post, whatever I deposit in a memory location has
> bit D4 ON. (i.e. if I Deposit 00 000 000, I get 00 010 000 when I
> Examine) So I have to check the wiring. I already cleaned the edge
> connectors. The wiring is a little more involved...
> Any other idea for this kind of behavior?
> I posted a higher def pic of the wire wrap board. The board has an
> UART TMS 6011 and two 555. I believe that it was wired as a dual
> function tape recorder interface and serial interface. But it's a
> guess based on connectors as well as schematics in the binder.