[sebhc] The 8-bit Runt of the Litter: ET-3400

Walter Moore waltm22 at comcast.net
Sat May 29 15:24:40 CDT 2004

I guess I'm missing that important document also!  I'm also missing the
schematic for the ETA-3400, so I cannot guarantee what I'm about to tell you
is 100% accurate.  It would be nice to see if the wires in 3 & 4 are

I compared an unmodified ET-3400 (no 'A', no 'Series') with one that was
modified and found the following differences:

1)	A 40 pin connector added (OK, I had to say that :) )

2)	D0-D7 connected on said 40 pin connector.  If you examine the back
of the board, you will find 8 solder pads for D0-D7 below the 40 pin
connector.  Each of these was soldered to the corresponding via (is that
what those holes are called???) next to IC9 and IC10 (to the side on an
ET-3400, below on a 3400 "Series").

3)	Pins 6 & 35 of the 40 pin connector (NC on the schematic) connected
to IC10 pin 1, soldered at the first via as the trace moves towards the top
of the board.

4)	Pins 15 & 20 (also NC on the schematic) connected to Ø2 near IC4.
Looking at the X-Ray layout picture, this was confusing to me.  It wire was
connected to the right pin of the 4x2 breadboard socket.  From the front,
this looks like it is labeled "Ø2", from the X-Ray it looks like "Ø2" is the
3rd pin).

5)	The RAMs were removed.

This system was purchased on eBay, and at least powers up.  I've never
hooked up a terminal or tape deck to try anything else out.

Do you have the Software Reference Manual (595-2271) for the ETA-3400?


> -----Original Message-----
> From: sebhc at sebhc.org [mailto:sebhc at sebhc.org] On Behalf Of Patrick
> Sent: Saturday, May 29, 2004 11:30 AM
> To: sebhc at sebhc.org
> Subject: [sebhc] The 8-bit Runt of the Litter: ET-3400
> Sorry if this ends up being a repeat... I sent from the wrong address...
> Does anyone have the instructions necessary to modify an ET-3400 for use
> with the ETA-3400 expansion accessory?  I have everything but those
> instructions.
> Thanks!
> Patrick
> --
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