30 Aug
2014
30 Aug
'14
5:29 p.m.
Time for an update. Here's where things stand (more like, where they lie)
at the moment..
I've replaced all of the ICs identified as bad on the front panel with
parts that test good - with a caveat or two. Some parts I'm just not sure
how to set up a thorough test for, but they failed the +basic+ test I was
able to set up, so I simply replaced those with parts that appear to be new
and in excellent shape (and that do pass the basic test).
So at this point, I have good reason to believe that both the front panel
and the CPU board have good chips all around.. none of the current chips
failed any of the tests I used to reject the parts they replaced.
But the machine is still missing its marbles - bearing in mind that my only
references are the Altair32 emulator and the documentation check-out
procedure. On power-up, the panel LEDs match the pattern on the emulator,
so that's good. But still, I can't get any sanity out of examine / deposit
memory locations.. nada. The ex. next and dep. next will walk up the range,
as indicated by the address LEDs, but I can't get any kind of data from the
data LEDs. They're either all 'on' or all 'off', in most cases.
I've tried this with the termination power both enabled & disabled, no
difference.
Unless anyone has a suggestion, I don't know what to do other than wait for
the arrival of the new SRAM board, and see how it behaves when that's
installed. Thing is, I have no real reason to doubt the existing DRAM board
- other than the fact that I've been warned off of using DRAM with the
original 8080A CPU board. And again, I can't say that the DRAM board is any
more alive than the socket it's stuck in..
Any ideas? SRAM should be here on Tues or Weds.
On Fri, Aug 29, 2014 at 9:51 AM, drlegendre . <drlegendre at gmail.com> wrote:
Had to do it, 16K SRAM board on the way from the
'bay. It's ostensibly a
working pull, but offered as-is - which in reality, probably covers most of
the examples on-offer.
Anyway, a $30 gamble at worst. At least I'll have something else for
comparison, and no concerns about potential refresh issues with 8080As and
3rd party DRAM boards. For as to date, I've never detected any signs of
life from the current DRAM board.. I mean, so far the thing seems pretty
much as inert as the slot it's stuck into. =/
On Fri, Aug 29, 2014 at 1:14 AM, drlegendre . <drlegendre at gmail.com>
wrote:
On Thu, Aug 28, 2014 at 10:55 PM, Chuck Guzis <cclist at sydex.com> wrote:
On 08/28/2014 07:41 PM, drlegendre . wrote:
The other thing--if you've got the 4K DRAM
boards (...)
I don't - I have a single RAM board, and it's a 64K DRAM unit - see
previous posts in the thread.
I'm in need of a small SRAM board, and just about to bite the bullet and
buy one from eBay.