Recent content by gnupublic

The 8/blue is from Wühlenweber Gymnasium of Bergneustadt, a school in Germany. They had two PDP-8/E, one normal and this one in blue. This front was build from a DEC technician. This is done very professional and the switches looks like PDP-15 switches. The frontplate is a 2mm steal plate with...

Today, one week of holiday comes to an end. But it was great, today I finally got my PC04 running! I was able to load a RIM and a BIN papertape. The biggest problem are these aweful cables. The core wire is broken at the Berg connecter, where it is crimped. That is awful to repair. I tested all...

Last time I bring that thread to the top, yesterday I spend some hours and found a second bad IC. An 74H04 (E27). It did not invert a signal, that lead to some strange things. With this replaced, the MAINDEC-8E-D1HA runs fine. Both with and without the jumper for timeshare. Other than the DEC...

Hello, I would like to show one of my future tasks. Got the rack two weeks ago and picked up the tape and tape controller last weekend. Most about this machine can be read here https://versci.com/1080proposal/index.html . This is a great site with lots of information. Most files can be found...

Today I found E14 (7400) to be defect on the M837. Changed it and now OS/8 ist starting! The Maindec runs OK. That made my day.... Still PM837 to do.

Meanwhile I'm a few steps further, but still not ready. (I'm too slow) PM837: The Plessey PM837 was able to change the fields, but it was not able to do a RIB (Read Interrupt Buffer). A simple loop LAS-RIB-JMP showed that not all bits come into AC (AC5-11). This looked different with a working...

Thanks Dough for the kind words. There was one fan inside without spacers. Just nuts, I had to pull the screws while turning, to stop the nut from turning itself. It was a pain to get it out. The other fan had 3 spacer but without beeing fixed. So I had to find a solution for mounting the new...

Today I got the M4 brass spacer for mounting the SUNON 20W fans for the power supply of my pdp8/e desktop. The spacer are 30mm but the inner distance of the fans is nearly 31mm. So I soldered a washer on top of the spacer and cut a tangent line: This mounted to the fans should be stable...

I made a comparison of the chips and yes, the IC positions are the same. IC types are: Plessey DEC 74H00 N7400A 74H10 N7410A 74H20 N7420A 74H74 N7474A DM74H04N N7404A N8235B 8235B DEC N8251B 8251B DEC N8271B 8271 DEC N8881A 8881 DEC N8T380A 6380A DEC RC8266MP...

The bootloader was os8diskserver. I plan to do the tests next week, thanks for all the hints.

Yes it looks very similar! Next week I can put the cards side by side and see what types of IC's are used. I did no further tests with the plessey cards yet. Need more time...

While waiting for some parts to change the fans of my 8/e desktop, I took this card to look after it. I got it two years ago and did not do anything with it. I even was not able to get any information about it. The numbers 700292-100 or 700233-10 did not help. Until now my friend reminded...

Dough, I still have 3 spare of Signetics 314A. I have ordered 3 Signetic 314 (no A) on ebay and hope they will fit.

I was able to locate the problem with the buggy SR of the 8/e. Here are some timing signals from the defect one and a working one. The one that is working shows less Signals on SR->DATA. From this comparison it was easy to track the Problem to E15 a DEC314A that was broken. This has to mask...

With the reed switch it seems to be 36° per switch, so it is exact 180° like the printing on the front panel graphic. The normal switch is a bit less, I guess 33° per switch. Thats is the difference between and So the panel of my 8/e is for the normal switch. From the production dates...