[GreenKeys] Can't stop getting old TUs

[David I. Emery]

On Fri, Jul 27, 2018 at 01:25:45PM -0700, Pete Lancashire wrote:
> Pulled my HAL ST-8000A out of storage, need the power connector (have them
> but cant find yet, will pay  a good price to speed things up)
> 
> Will soon get a Frederick 1280A. Does  not power up but no burnt boards or
> smell. Anyone have the schematic of the power supply.

	I have the entire (nsg.com version) of the 1280A manual EXCEPT
for the AC PS schematic.  I think they are a known weakness, and maybe
they wanted to keep the repair revenue for themselves.

	I DO have a parts list and some info about what manufacturer
part numbers were for the AC PS parts (in a 1280 rather than 1280A
manual) and a board layout, and outline drawing - but no schematic.  
That page was missing from my manual copy.   It is listed in the index.

	I'm interested - from an engineering history standpoint - in
finding a schematic and block diagram of the ST-8000A as I'm quite
curious as to how similar the actual analog demod circuits and filters
are between the two designs.

	As I understand it Fredrick designed the 1280 some time in the
late 1970s or very early 80s in response to a "military" contract
request.. (probably for NSA sigint systems) and some number of them were
made and shipped and either stored in warehouses or put in service in
systems during the eighties.

	And apparent the same basic spec was put out for another bid
around 1990 soliciting alternate suppliers - and HAL developed the
ST-8000A based on both the 1280A and the ST-8000 to meet that contract
(and supposedly about 730 or so of those boxes were made and many just
warehoused and eventually surplussed).   One requirement of the second
contract was drop in compatibility with the 1280A as I understand it so
there are many similarities.

	At one time I had a ST-8000A manual somewhere in .pdf form but I
can't find it... and the recent greenkeys discussion of the two boxes
has got me curious as to how much and in what way they differ in respect
to the actual demod architecture, filters, and overall performance on
typical HF signals.

	There are, of course some control panel user interface
differences.

-- 
  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."