-----Original Message-----
From: Tony Duell <ard_at_p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Tuesday, 30 March 1999 6:43
Subject: Re: Decwriter II
>The paper out logic is pretty simple. The output of the switches goes
>through a little RC circuit to the input of a 7474 d-type (unfortunately
>which chip this is depends on the board version - it's E5b on an M7723
>and E34b on an M7728). The output of that ff is the ready line.
marvin was kind enough to post similar data. Looking at that area this
afternoon.
>It appears that the switch is closed when the printer is out of paper. So
>my first test would be to find the 100 Ohm resistor between the D-input
>of that chip (pin 12) and pin BB on the keyboard connector. Unsolder it.
>This disconnects all the switches. Does it work now?
No.
>I don't, alas, have the schematic of the chassis. But it appears from a
>general wiring diagram that the paper out switch is in parallel with the
>cover interlock switch. Have you checked that one?
Yes. the switches are not implicated. I disconnected the whole switch
assembly, still no go. Stuck output on the chip I'll bet, the fact it was
intermittent for a while makes a logic chip failure even more likely. (I
don't think I mentioned that earlier)
Thanks for your help......
Cheer
Geoff Roberts
Received on Mon Mar 29 1999 - 20:09:07 BST