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Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!sun-barr!cs.utexas.edu!uunet!ycomp!root
From: root@ycomp.UUCP (The Super User)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: HELP ... with 7300 printer device
Summary: Having same problem!
Message-ID: <99@ycomp.UUCP>
Date: 13 Jul 89 17:39:09 GMT
References: <124@UNIXPC.UUCP>
Followup-To: unix-pc.general
Organization: Y-Comp Inc., E. Longmeadow, MA
Lines: 41


I have what appears to be the exact problem with a board just back
from San Leandro. If I 'cat' to /dev/rawlp 1 line at a time it works OK.
More than 1 line at a time results in mostly garbage. Diagnostics work fine.
My guess is that the BUSY line is not working correctly. The board they
sent back (I don't think its the same one I sent them) has 'REV H' on it. I
first thought they had sent me a bad board, but...

Time for a closer look at the board.

AH HA!! Someone has soldered a diode across a capacitor that comes off of
pin 11 (the BUSY line) on the parallel port. I wish I had another board handy
to see if it has this mod. I really don't feel like disecting another machine.
I wonder what will happen if I remove it. It's worth a try.

Works fine now!!!

Either they put the diode in backwards or they put in the wrong place. It
can't possibly work the way they had it (with the cathode to ground) as
it would short the BUSY signal to ground.

If anyone has a board they can look at, I would be interested to know if
they have this diode and where & how it is connected. There are 4 small
caps between 2 resister packs just above the printer port as shown below.
Mine had the diode across cap 1 with the cathode (banded end) up.




	| 1 2 |
	| 3 4 |
        |     |

        __________________
	|  parallel port |
        |                |

I probably would have sent the board back to San Leandro until I saw Ted's
request for help. I hope this helps someone else also.

	Bob Campbell