Heathkit ETA-3400 vs. ETW-3400 confusion?

[william degnan]

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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