This an H8 card "extender" that ostensiby allows you to raise one of your H8 boards up
so that you can work on it while in the machine.
You know, check address lines, voltages, etc.
It's called an HTB-0 and was manufactured by
Bob Mullen in 1979.
It comes with its original box and doc.
So I've never found much use for this board for its original purpose.
I simply found it too difficult to use.
But I DID find a great use for it!
I attached a breadboard to the HTB-0 with removable sticky foam tape,
and wired an Arduino Nano memory-check circuit to it.
You can plug this board into your 16K memory board
and run it through a memory check.
You'll need to use a serial program like Putty or the
Arduion IDE to see the Nano's output, which shows the
board being checked, and will specifically identify
any mis-behaving chips.
The source code for this memory check program can be found
here.
It can easily be modified to check 8K or even 64K boards.
Also, the memory check isn't exhaustive,
but seems to work good enough to find bad chips.
It even helped me find that bad address line on one of
my 16K boards.
There is a 9v power supply that is fed to the H8 board
through the only modification to the HTB-0.
The H8 board's 5v regulators turn that into appropriate
power for the board.
You can easily remove this memory check circuit and use
the extender as it was designed.
However, I find the memory checker far more useful.
