TRS80 Model 100 technical questions

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Thu May 1 19:02:00 2003

> Hi all,
>
> I got a TRS80 Model 100 in and need some technical info:
>
> -what is the polarity of the DC-input on the socket?

According to the schematic in the printed Technical Manual, the connector
is centre -ve.

>
> -Is a filtered 6 volt DC voltage ok or has it to be stabilised?

The mains adapter replaces (electrically) the 4 internal AA cells when
it's connected (there's a switch in the input conenctor that disconnects
the internal battery +ve terminal when you put the adapter plug in).
Therefore, the adapter doesn't need to be well regulated (since the
batteries aren't). There's a fairly complex DC-DC converter on the main
PCB to produce +5V and -5V from the batteries, and that provides
regulation too. I think the official mains adapter (at least the one sold
in the UK) was just a transformer, rectifier and smoothing capacitor.

However, I'd not want to apply a voltage wildly different from 6V to the
machine. It will probably be OK, but I don't fancy rebuilding that DC-DC
converter if it's not :-)

-tony
Received on Thu May 01 2003 - 19:02:00 BST