TRS80 Model 1 Fixup - Part 2

Included in Ian's box of "things from the junk box" for FreHD testing was a Model 1 Expansion Interface PCB.


Ian tells me that a common problem is people shipping Expansion Interfaces with the power transformer still inside.  Add an enthusiastic courier driver and you are almost guaranteed to have a broken case. This Expansion Interface had such treatment so had ended up a junk box parts donor.


Apart from the missing case, WD-1771 floppy disk controller and connection cable to the keyboard, the Expansion Interface board looked complete and in good condition.


For anyone who finds a parts donor Expansion Interface board and wants to get it going, as of 2013 the WD-1771 floppy controllers are still available on eBay as are the 4116 dynamic RAM chips.  Best to search around because the prices vary a lot.  Unless you are hung up on period authenticity then the vintage style packaging with the really high prices are not required!


With the chips replaced and a cable made up the initial indications where that the Expansion Interface worked fine.


At this point I realized why they put these in cases... where to put the monitor when you just have a PCB? Things get very spread out.


Taking inspiration from the current trend in acrylic project cases for things like the Raspberry Pi I went looking for a source of acrylic sheet and discovered CTS Plastics in Tauranga.

Here is my solution to the no-case problem.

    2 sheets of 6mm grey perspex plastic

    5 x 50mm bolts, assorted nuts and washers.

Total cost about NZ$25.

 

Much safer than having the EI board floating around on the table, looks smart and with 6mm perspex it is very strong so the monitor can sit on top.

 

The dimensions and drilling information is in the attached pdf for anyone wanting to build their own.

The drill details are:
 
    4 holes (1 at each corner) 20mm from the edges.
 
    2 holes 143mm from the left edge.  One is 82mm from the bottom and the other 202mm.
 
    1 hole 38mm from the right edge.  This is 142mm from the bottom.
 
The two pieces will be mounted together with spacers so the holes need to be accurately drilled on both sheets.

 

 

 

 


 

 

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Contact Andrew Quinn

jaquinn@ihug.co.nz http://twitter.com/jaquinn