This post describe my effort to fix a broken M8044 PDP11 RAM module. For tracing down the bug, I’ve used QBone.
I own a defective M8044 RAM board. This board came as part of my OBA-11 PDP11. It was obviously checked by DEC, found to be broken and has a red defective badge.
Setting up test bed I’ve created a testbed, consisting of:
QBone An unused backplane H9278-A with 8 slots The device under test, the M8044 As power supply, I took a 5V/4Ampere power supply from my parts bin +12V (used by M8044) supply comes from a lab power supply First test with QBone: Check if board responses to bus requests QBone has its tests and many features in a single executable.
What is QBone? QBone is a fascinating project by Jörg Hoppe. It is based on a PDP QBus module that can be inserted into any QBus backplane. It implements all features required by the QBus, so this module looks like any other QBus module from the PDP11 perspective.
The module integrates a BeagleBone Board (BBB). This is an ARM-based modern computer, like Raspberry PI. The biggest advantage of BBB over Raspi is: that the board contains two separate I/O processors called PRU (Programmable Realtime Unit).
My DEC VAX 4000 boards All boards seem to come from a VAX 4000-300 machine. See http://gunkies.org/wiki/VAX_4000_series
ebay seller text
DEC VAX 4000-300 Boards CPU KA670 L4000 in Module Plastic Case (99-08536) 2x MS670-CA L4001-CA und 1x64MB Clearpoint Memory KA670 CPU board 22 Bit QBus board. CPU clocked with 143 Mhz. CPU chip is called REX-520 There is a FPU on board called CD523.
Built-in Ethernet and 2xDSSI (disk) controllers
Over the years, I’ve owned several logig analyzers. For a long time, I used a Tektronix HP1241 and later an HP 16500 These were large and heavy devices, weighting twenty kilos or more. Usually equipped with a noisy fan.
These old logic analyzers usually suffer from a very small capture memory of some kilobytes. If you know the exact situation where some hardware situation to be tracked occurs, then this is ok.
DEC Digital OBA11-MF bought in poor condition from ebay. It has no case, has some physical damage. Sold of course as defective.
All together this seems to be a kind of “embedded” PDP 11/03 with only a bare minimum of boards and no intention for extending it later on. Maybe used as a control unit in some chemical plant or whatever. here someone has a picture of another device like this.
I own some old PDP11 parts. I try to complete these to have a minimal set of cards to boot the PDP11. This is seen as a long term task and may last several years…
Activity was started in February 2017. In January 2021, I have spent 91+161+3*90 = 522€ on that madness, without any results so far :-) .
In 2022, I could buy a basic PDP unit, without case and in bad condition.
Einfache Löt- und Entlötstation. Gekauft vor ungefähr 10 Jahren. Funktioniert sehr gut.
03/2022 wurde der Lötkolben nicht mehr warm. Vermutlich Heizelement defekt. Das Gerät zeigt direkt nach dem Einschalten kurz “u01” an, evtl. eine Firmwarenummer.
Am Lötkolben-Stecker sind 4 Kontakte, zwei für den Thermofühler (rund 2,4MOhm bei 25°C) und zwei für das Heizelement. Ich messe am defekten Kolben 2,2 Ohm. Meine Vermutung ist, dass das Element einen inneren Kurzschluß hat. Es handelt sich um einen 24 Volt / 60 Watt Lötkolben.
DEC Keyboard LK401 has serial interface, 4800 Baud, 8N1. See more information on the keyboard hardware here.
The keyboard is solid and heavy, has superb tactile keys and is of the old 80ies quality. That you simply cannot order on Amazon or so.
For a long time, the keyboard was supported by the Linux kernel, but this time is gone.
My idea: connect the keyboard to a microcontroller that can connect to a PC via USB.
This keyboard came in as part of a Digital DEV VT402 terminal. I have some information on that terminal here . After some time, I found that the keyboard of that terminal is also an interesting kind of thing.
DEC LK401 Hardware DEC Keyboard has a serial interface. The connector to plug into a DEC VT420 terminal looks like an old telephone connector, with 4 pins, called RJ10.
An Intel 80C51 microcontroller handles most of the keyboard functions We can see also the Beeper and a 7.
