The Drastik 1 48k does not interoperate with an un-modified TRS-80 Model 1 Expansion Interface as the memory data bus buffers in the EI are always enabled for the top 32k of memory even if no RAM is installed.

It is necessary to disable the data bus buffers if the top 32k on the Drastik is to be used. This requires one track cut and and addition of a 10k resistor.

Step 1

Remove all power and connectors from the EI and turn it over so the bottom is facing up.

Step 2

Remove the four screws to reveal the main board

Step 3

Locate the eight or sixteen 4116 RAM chips and carefully remove them from their sockets using a small flat-blade screw driver or specialised IC removal tool. Store these ICs safely for later use if required.

Step 4

Locate the track that needs to be cut

Step 5

Cut the track in the location below

Step 6

Solder a 10k resistor between the isolated track and signal ground as follows.

Step 7

That’s it! Re-assemble and test