Ritzert@DMZRZU71.BITNET (06/30/89)
Hello DesJet+ Users! Warning!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! DON'T USE THE "DESKJET PLUS" AT THE PARALLEL PORT OF THE ST !!!!!!!!!!! (without additional hardware) I JUST KILLED THE ST'S PARALLEL PORT WITH THIS PRINTER. Background: We've been using a DeskJet with a Mega2 as a TeX-System (the fast driver by TOOLS GmbH) heavily for nearly one year without problems. Today I attached our brandnew DeskJet+ to our second machine (an ST4 with a 16 MHz CPU) and tested the system's performance doing hardcopies at 100dpi and TeX-Output at 300 dpi. The TOOLS software is so fast that the DJ+ prints at its maximal speed. After a lot of screen dumps without problems I printed the first TeX-document, a small letter with about 10 lines except header and was amazed by the printing speed. When I tried to print the secont TeX-file the printer wasn't accessible at all any more. I switched off everything for about an hour and then did a second try --- nothing. Was it the printer port or the DJ? Well, I attached the older printer to the computer. Again, no response. So, obviously, I killed the printer port of my computer. Why did the DJ+ destroy the ST's port and the DeskJet does not? And why didn't I have any problems printing text or low resolution graphics? Well, I guess the reason is the high data rate through the port which occurs when the fast printer does graphics on its maximal resolution. Due to this higher data rate the mean current per unit time is (several times!) higher than with the slower DeskJet. This higher average current probably was too much for the weak printer port of the ST (please excuse my german english). One further support for this idea: even the DeskJet (not the +) does not print 300-dpi-TeX-files with >absolutely< no problems. Sometimes at the outer right margin some strange irregular dots appear. Solution: switch off the computer for 10 minutes and afterwards do a second try. So, concluding: if You want to use the DJ+ with the ST use either the serial port or put a "Leitungstreiber" into the connection. If You intend to print straight text and no graphics at all you probably will have no problems due to the lower data rate. In its 10/88 issue (p. 134ff), the German computer magazin c't published a simple do-it-yourself solution using two 7407-ICs and a Capacitor of 100 nF. Alternatively, You can buy a printer cable with these ICs built in. In Germany it costs something of the order of 70 DM. I thought I din't need it. Now I know better. Michael Ritzert Institut fuer Geowissenschaften Abteilung Geophysik Universitaet Mainz 65 Mainz BRD bitnet: mjr at dmzrzu71