24 Aug
2014
24 Aug
'14
10:10 a.m.
If it were me (and it's not, so FWIW) I'd continue to work on this since
you seem to be making good progress, but I'd pick up some boards from
the N8VEM-S100 group instead of modifying (as opposed to repairing)
vintage gear.
Boards available and contact information is at:
http://n8vem-sbc.pbworks.com/w/page/35044530/PCB%20Inventory
Of course you have to source components and build them yourself but
that's a lot of fun.
Todd
* drlegendre . <drlegendre at gmail.com> [140823 20:20]:
Ok good call gents, thanks for pointing this out..
yes, the LM309 only
provides power for the termination network (marked VT+). Here's what I see
in the network:
- Some lines have no connection to the network at all
- Most lines have a 330R pull-up connected to the VT+
- A number of lines are biased at +roughly+ 1/2 VT+ by being placed at the
junction of a 330R and 470R -> Gnd resistor.
And for some reason, all of the data lines - with the exception of D2 - are
in the latter category. They're biased at the 330 / 470 junctions. So my
current questions are..
Why did they skip D2 of all things?
Will any of this have any effect on the operation of the machine, once I
plug in an original CPU board & static RAM board?
And lastly...
Does anyone have a 1K or 4K static RAM board for this, that I can beg, buy,
barter or steal off them? Howzabout an original mainboard, so I don't have
to whack this one to pieces.. which seems to throw up huge red flags in my
mind, as I'm loath to modify or damage any kind of vintage parts!