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    H740 Power Supply, what's your Q1?

    H740's in my gear:- PDP8/F: MJ2500 PDP11/05: TIP645
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    My first Omnibus interface - Progress so far

    I've done a bit more on this, but want to take a break and play with other toys, so for anyone interested, this is the project so far. Schematic, PCB files, firmware, software is in the attached zip. This is NOT a finished & polished project. The documentation above is for interest only. But...
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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?

    Here is my first attempt at a home-made Omnibus interface card using these adapters. It's a mash-up of the boot-loader designs by Malcolm Macleod and Roland Huisman, plus some extra stuff (power supply voltage monitoring, and provision to read the memory address and memory data buses) Yes, I...
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    A general purpose Flip Chip adapter board - Worth doing?

    A couple of weeks ago, I had some of these adapters made by JLCPCB. As suggested by Roland, I didn't bother with the ENIG Gold fingers (and it would have near doubled the price). The boards are too short for the fab to do the beveling, so that must be done manually on some sandpaper. For...
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    A general purpose Flip Chip adapter board - Worth doing?

    Good to hear that non-rectangular boards don't cost much more. I've only ever ordered rectangular boards, so I was worried that it might significantly add to the cost. I've also never ordered boards with edge connectors, or gold plating, so I'm also concerned about specifying all that correctly...
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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've updated my Omnibus Signals List, fixing some errors, and adding three new fields. Two of these fields refer to information contained in Chapter 9 of the "Small Computer Handbook 1973" The new fields are:- * A 2 digit "Load Driver" that indicates the Load and Driver types, as per those shown...
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    Videos: Testing DEC H740 PSUs and PDP-8/f power on & simple tests

    Thanks for that. H7450-Mod-1 I've added the missing circuitry, trying to abide by the existing layout, and with DEC's. But VCFED won't let me upload RAR or ASC. Where can I put them? H7450-Mod-1B My idea of how it should be drawn. Notes: (Designators below are as used in...
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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

    This is the H740 schematic. It appears to be self-oscillating (a relaxation oscillator?). For interest, the H740 power elements are similar to the H777, which is well documented in chapter 3 of "BA11-L mounting box technical manual". http://bitsavers.informatik.uni-stut...-001_Oct77.pdf But...
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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...