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    My first Omnibus interface - Progress so far

    This is my first Omnibus interface card, using the flip-chip adapter boards shown in this thread:- https://www.vcfed.org/forum/forum/genres/dec/1228572-a-general-purpose-flip-chip-adapter-board-worth-doing It's a mash-up of the boot-loader designs by Malcolm Macleod and Roland Huisman, plus...
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    A general purpose Flip Chip adapter board - Worth doing?

    There's a bunch of projects out there for "after market" and DIY boards for DEC machines, targeted at Unibus, Omnibus, Qbus, and possibly others. These projects include: extender cards, prototyping cards, Unibone, QBone, MOS memory boards, Boostrap card emulators, etc. What they all have in...
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    Video: M8650 working on PDP-8/F

    For anyone who might interested, a video where I get my PDP-8/f to do some I/O at last. Using the M8650 board for serial communications (but only at 110 baud). https://www.youtube.com/watch?v=qa1jhO37umw
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    M8650 annotated schematic, with highlighted Omnibus and Berg connector pins

    The annotated schematic for the M8650 at:- http://tronola.com/M8650_schematic_annotated.GIF is a pretty clear copy of the schematic, and the annotations look useful. But the external connections to the board are all over the place in the original DEC schematic, and the annotations did not...
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    List of PDP-8 Omnibus signals

    I wanted, but could not find a cleanly formatted list of the PDP-8 Omnibus signals. So I've created the list below from Appendix B of the "PDP-8/e/f/m MAINTENANCE MANUAL VOLUME 1" Please let me know if: - Such a list already exists - This list is of any use at all - There is a mistake in my...
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    Videos: Testing DEC H740 PSUs and PDP-8/f power on & simple tests

    A couple of PDP related videos. First video is testing the H740 power supplies from the PDP-8/f and PDP-11/05, with a dummy load. I made the mistake of running the first PSU from a variac with the load attached, and damaged it. The second PSU blew a fuse under load, not sure why. After...
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    Dummy Load for DEC PDP computer Power Supplies

    A while ago I made this dummy load for testing the H777 power supplies in my PDP 11/04 and 11/34. And I have three other PDPs that have power supplies that need to be tested. But I was too lazy to allow for them when I made the unit above. So now I've made a more versatile version. The...
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    Corona Data Systems PC-400 quick look

    A quick look inside a Corona Data Systems PC-400. A desktop model of an early IBM PC clone/compatible, made in 1983. https://www.youtube.com/watch?v=Nc9r8jLupv0 Manual link:-...
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    PDP-8/F Quick look and Teardown

    Leaving the best to last, here is the pride of my PDP collection, the PDP-8/F. Here we just open it up and have a look around. The power supply and its capacitors still need to be tested before I'll try to turn it on. https://www.youtube.com/watch?v=wAstB-dCvg8
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    PDP8/A - Quick look and Teardown

    Even though none of them are yet operational, I've been messing about with PDP-11s for long enough now. It's time to have a quick look at my PDP-8s, starting with the PDP-8/A. https://www.youtube.com/watch?v=aEq2K7ylXjc
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    PDP11/05 - Quick look and Teardown

    A quick look inside a DEC PDP11/05, made in Ireland back in about 1973. The power supply has some bad electrolytic capacitors, so power on and tryout will have to wait until they have been replaced. https://www.youtube.com/watch?v=JA9q6E1sv1I
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    PDP-11 /04 and /34 CPU tryouts: FAIL and FAIL!

    Having previously tested or repaired the power supplies, console interfaces and memory boards of my PDP-11/04 and 11/34, it was time to try inserting the CPU boards into them. Just before powering it on I noticed something on the 11/04's CPU board (M7263) that I had stupidly neglected to...
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    PDP-11/04 & 11/34 - Testing the M7847 Memory Boards

    I've made a lot (too many?) of videos about my PDP11/04 and 11/34 computers, but have not yet got past messing with the power supplies and the console interface. So it's high time to start moving towards running systems by getting more parts of them running. The next logical step is the memory...
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    My pdp-11/34 has an Easter Egg!

    While repairing the M7859 board in my pdp-11/04, I learnt a lot about the workings of this board. My pdp-11/34 has the later version of the M7859, and look what it does! https://www.youtube.com/watch?v=_j0rE9StCs8
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    Tryout and teardown of two Tandy Colour Computer 2s

    To help with repairing my Compacta Uniboard, I was looking for a working 6809 based system to help develop a ROM emulator gizmo using a RAM chip. I have an old Tandy Colour Computer 2, that I tried to fire up after 35 years of storage:- https://www.youtube.com/watch?v=7gvMJ6ilvAU No joy...
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    How to creating Flex-usable physical floppy disks, and writing to them?

    I plan on soon trying to get my Compacta Uniboard (a 6809 Single Board Computer) operational, and ultimately get it to run Flex. It has a 34 way interface for 5" floppies, and a 50 way interface for 8 inchers. Obviously, I'll need to get the Flex disk images onto physical disks, and with just...
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    Compacta Uniboard - A 6809 SBC cicrca 1982

    A while ago, I posted this stuff in the retro section of the EEVBlog forum, and just realized I should have put it here also. Some time in the 1980's (judging by the latest date code, about 1985) I bought and assembled this "Uniboard" by "Compacta Incorporated". They supplied just the PCB and a...
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    PDP-11/04 Console Repair - Part 1

    Continuing with my PDP11/04 and 11/34 repairs, now that the power supplies are sorted, next comes the console and its interface, the M7859 board (together termed KY11-LB) These work properly on the 11/34, but there are multiple issues with this section of the 11/04. Having a working set of...
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    KY11-LB (pdp11/04/34) "Documentation error" & block diagram

    After cleaning up and sorting out the PDP11/04/34 power supplies, I'm starting to fire up my two machines with boards inserted - first off, just the M7859 console interface and the M9302 terminator board. I knew of the documentation error in the manual EK-KY11B-MM-001, regarding the orientation...
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    Broken button on DEC PDP-11/04 KeyPad

    So this ham-fisted clown was cleaning the front panel keypad of my 11/04, and not knowing how fragile they were, broke one of the buttons off. The buttons are part of the frame, all being a single piece of plastic, but they are joined to the frame body only by a thin bridge at the top of the...