On Tue, Jun 7, 2016 at 1:58 AM, drlegendre . <drlegen...@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...@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. -- @ BillDeg: Web: vintagecomputer.net Twitter: @billdeg <https://twitter.com/billdeg> Youtube: @billdeg <https://www.youtube.com/user/billdeg> Unauthorized Bio <http://www.vintagecomputer.net/readme.cfm>