Decwriter II

From: Computer Room Internet Cafe <>
Date: Mon Mar 29 20:09:07 1999

-----Original Message-----
From: Tony Duell <>
To: Discussion re-collecting of classic computers
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

>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?


>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......


Geoff Roberts
Received on Mon Mar 29 1999 - 20:09:07 BST

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