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    OS/8 questions

    I have been puzzled for a while about the delay of about 1 - 2 seconds in the output of the OS/8 DIR command for larger directories. This delay is very pronounced when your serial speed is 9600 bps or faster. Interestingly on my PDP-8/E with AC selected for display you also see some distinct...
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    PDP-11/04 and 11/34 front panel

    The PDP 11/34 and 11/04 front panels (both operator and programmer) use a somewhat stiff plastic sheet of 1.0 mm thickness with DEC logo, model designation, labels for the keys printed on it, cut-outs for the keypad and knob and red transparent sections for LEDs and 6 digit 7-segment display. I...
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    Serial PDP-8/e like computer?

    I have been thinking about building a PDP-8/e clone using TTL logic and SRAM for memory but designing the CPU as a serial CPU like the PDP-8/s. Rather than cloning the 8/s I thought it would make sense to make it functionally like an 8/e so that 8/e software would run unmodified. This could be...
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    M7846 RX11 Unibus floppy controller board documentation?

    I was unable to locate schematics and/or a maintenance manual for the Unibus M7846 RX11 floppy controller board. If anyone has these could you please scan them and make them available. Thank you. Tom
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    Theory of operation of H7441 regulator

    The DEC H7441 regulator is a relatively complex circuit using two 555 timers and two LM301 op-amps. I am struggling to understand how it is meant to work and was hoping to find a maintenance manual for it. Could anyone with such a manual please help? Alternatively is there another explanation...
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    PDP-11/34 restoration

    I am restoring a PDP-11/34 in what I think is a BA11-K box and found the 11/34 related manuals & drawings on Bitsavers. While restoring my LAB-8/e and PDP-8/e I found the 8/e maintenance manuals with detailed theory of operation very useful. I could not find the same level of detail for the...
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    Desoldering components video from PACE

    I have just stumbled across a very good video about desoldering techniques using a vacuum desoldering iron: Component removal on DEC (and other) boards can be tricky because often the parts are retained by bent pins.
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    Tektronix 4010 restoration

    Last Sunday I picked up a very dirty and corroded Tektronix 4010. I spent two days on disassembly and cleaning and now I am looking for advice on getting the terminal going again. Roland Huisman had some of the same issues as documented in this 3 year old thread...
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    U/W FOCAL V4E with EAE support on paper tape

    Is there a stand-alone paper tape version of U/W FOCAL V4E which uses EAE?
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    LK201 key cap removal

    I would like to clean the filthy key caps of the LK201 keyboard I got with my DECmate III. Like several other keyboards in the past I tried my key cap remover gadget to pull one of the function key caps off. I got the key cap off, but one of barbs broke off. 😢 These barbs hold the key caps...
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    BM08 or BA08 for PDP-8/L

    I have created this thread for discussions about possible chassis extensions for a PDP-8/L to avoid polluting other threads. ;)
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    Extended Arithmetic Element (EAE) re-implementation using current TTL ICs?

    As this subject has come up a few times in other threads I have created a new thread just for this. What would be the interest for a new PDP-8/e/m/f "Extendend Arithmetic Element" (EAE aka KE8E) board set re-implemented using currently available TTL ICs? Roland Huisman has done similar work...
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    VR14 TO-3 heatsink socket?

    I finally got around to replace the dead TO-3 power transistors in my VR-14. They are mounted on the power supply regulator heat sink using TO-3 sockets made by AUGAT. Unfortunately one of the sockets has been broken by somebody in the past by over-tightening the transistor mounting screws. This...
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    VR14 ECOs

    Does anyone have the DEC VR14 display ECOs in PDF or paper form? There were some changes to suppress arcing which appear to be implemented in the VR14 in my LAB-8/e but not in the second VR14 which was part of a GT40.
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    VR14 "meltdown"

    After running my newly built VC8E in my PDP-8/e beautifully displaying on a VR14 sadly the fun suddenly came to an end. 😢 The 3A line fuse of the VR14 had blown and of course the replacement fuse blew immediately too. After some probing with a multimeter I found that the +/-22V power...
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    Bridge rectifier in VR14

    The VR14 uses a bridge rectifier made up from two "half-bridges" with two diodes each. The writing on the rectifier says "MDD DM 15". The parts list in the DEC VR14 Engineering drawings refers to it as "DM-15". Does anyone know what this part is properly called and if there is a datasheet for...
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    Enhancement for Roland's VC8E

    I found that although Roland's version of the VC8E board set worked the X/Y deflection signals were very noisy and the VR14 display was less than perfect. This worried me as the expensive deflection amplifier transistors in the VR14 would be stressed by the noise. At first I suspected that...
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    CAD tool for DEC style mixed logic

    Is there a CAD tool which allows me to draw "mixed logic" as used in most DEC schematics. Example: The image above shows a logical AND of two active low signals AE1 and MA0IL. The actual physical implementation is a NOR gate. Bonus points for a software package which lets me draw and...
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    PDP-11/34 cable trouble

    I am making a second start on restoring a PDP-11/34 found in a barn. Some time ago I already removed the power supply assembly in the back and disconnected the many cables going from the power supply to the main chassis. The cables were extremely stiff as if the cable insulation had lost all of...
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    A225 Deflection Amplifier PCB

    Has anyone got a more readable scan of the A225 Deflection Amplifier PCB than what is shown on page 15 of: http://www.bitsavers.org/pdf/dec/graphics/VT11/VR17_Engineering_Drawings_Mar75.pdf The schematic on the following page is a poor print or scan too, but I found a few alternatives...
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