7 Jun
2016
7 Jun
'16
8:01 a.m.
On Tue, Jun 7, 2016 at 1:58 AM, drlegendre . <drlegendre at gmail.com> wrote:
@Tom & All,
"In following this thread, and taking in my "vast" Heathkit knowledge, I
can only assume that the addition of a 'W' in the model number is to
indicate a WIRED (at the factory) Heathkit."
Fair enough, and it's as good a suggestion as anything heard so far. But
again, you're confusing the (very easily confused) model names..
The ET-3400 and ET-3400A are the original "trainer" kits. These are the
main computer module, with a calculator-style keyboard, 7-segment LED
display, and either 512 bytes or 1KB RAM memory. I believe that the later
'A' version also includes the 4MHz crystal-controlled system clock upgrade,
in addition to the larger RAM size.
The expansion modules are confusingly called out as ETA-3400 (note, not
ET-3400A) and ETW-3400. It's these latter two distinctions that are the
cause of my (and apparently, much) confusion. But your suggestion that the
'W' substitution refers to a factory-wired unit makes good sense, at least
in this case - because my ETW-3400 seems to have been factory built.
It doesn't have any of the tell-tale signs of kit assembly. For instance,
it appears that the board has been wave soldered and washed of flux. The
rest of the workmanship gives the same impression of factory-quality
assembly.
So maybe that's all there is to it? The ETA-3400 is kit form, and the
ETW-3400 is factory built?
On Mon, Jun 6, 2016 at 10:19 PM, Tom Watson <tsw-cc at johana.com> wrote:
In following this thread, and taking in my
"vast" Heathkit knowledge, I
can only assume that the addition of a 'W' in the model number is to
indicate a WIRED (at the factory) Heathkit.
This may mean that the ETW-3400(a) is a wired version of the ET-3400(a).
The difference that shows between the 'a' and non 'a' version is the
space
for four ram chips in the upper left visible
corner of the PC board. The
non-a version can have up to 4 ram chips (for a total of 512 bytes), but
the a version has two 1024x4 chips, but only 512 bytes are available.
Hope this answers some questions.
(I have an ET3400-a version).
From the Modification Kit page 1
"This Modification Kit will let you interface the ET3400
and the ET-3400A Microprocessor Trainers with
the ETA-3400A or EWA-3400A Microprocessor I/O
Memory Accessory...."
".....The following steps will modify your Heath ET-3400
Microprocessor Trainer so it will operate with the
ETA/EWA-3400 Memory I/O Accessory....."
There is a manual for the ETA that includes both Tiny Basic and Wintek
monitor.
It just makes sense to me that T = Tiny Basic (and Wintek monitor), EWA
means Wintek monitor (only).
To prove this, find the manual entitled: "SOFTWARE REFERENCE MANUAL for the
MEMORY AND INPUT/OUTPUT ACCESSORY for the ET-3400 Trainer Model EWA-3400
The ETA version part number is 595-2271-01, the EWA must be close to that.
Back then, getting an extra BASIC ROM would have been a measurable expense,
especially for a school that had no use for BASIC to be included in their
trainers.
--
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