IMSAI 8080 (our show so far...)

From: Dwight Elvey <elvey_at_hal.com>
Date: Wed Jun 30 11:26:14 1999

"Bill Sudbrink" <bill_at_chipware.com> wrote:
>
> 1) Front panel assembly instructions. The 16 pin cable
> is installed on the correct side of the board (not on the
> component side). However interpretation of pin one is
> vague. I quote:
>
> CP-A TO MPU-A INSTALLATION
> 30) Using the 16 conductor ribbon cable with 16 pin
> 3M dual inline connectr, insert one end into the
> hole pattern U2 from the back side of the CP-A board
> so that it can be soldered from the front (component
> side) of the CP-A board. The cable should be mounted
> so that it extends upward from the top of the chassis
> when the board is mounte.

Hi Bill
 I thought for sure this was the issue. I would still suspect
that there is a problem in the cable connections. Either
by error in assembly or by error in design of the CPU card.
I forgot to look at the schematic last night so I still don't
know what would be the best solution. There is little question
in my mind that the data wiring is swapped at the cable.

>
> End quote. Which end of the cable you choose to solder
> to the CP-A will changed the orientation of the red
> (pin 1) stripe.

 This shouldn't be a problem. As you noted, you tried flipping
the header connector at one end and it didn't work. The way
these ribbon connectors work, no matter how you put them on,
the corner that is pin 1 will either be pin 1 or the opposite
corner( pin 9 ). Pin one can only come out in two places. That
is why I suggested that the header might be on the wrong side of
the board. That is the only way that pin 1 can get swapped with
pin 16 or pin 8. The end of the cable would make no difference
at all as to which connection pin 1 was unless you installed
it upside down. This is one of the main features of using
ribbon connectors.
 It seems like someone had a gif file of a IMSAI front panel on
the net. If someone remembers what the local was, I'd look at it
and see what we can do. Do you have the stated pinout of the cable?
Maybe that would help. There is one other thing that might still
be the problem. One end is not crimped correctly. If the cable
is twisted a little, some of the connections could be crossed
to the wrong side of the connector. Anyhow, if you can get me
the pin and signal names, I'm sure we can make progress.
Dwight
Received on Wed Jun 30 1999 - 11:26:14 BST