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  1. Replies
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    107

    Maybe have a look at this online version?...

    Maybe have a look at this online version? https://manx-docs.org/collections/mds-199909/ Although this might not have PDP-11 stuff.
  2. Thread: Micro PDP 11/73

    by cruff
    Replies
    5
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    217

    Do you know what boards you have in it? Is it in...

    Do you know what boards you have in it? Is it in a BA-23 rackmount/deskside enclosure? If so, you might find EK-186AA-MG-001 the BA23 Enclosure Maintenance guide to be of some use, but that doesn't...
  3. A SCSI disk drive normally formats the entire...

    A SCSI disk drive normally formats the entire disk in response to the format command. I don't remember if I saw any drives support partial reformatting.
  4. My IIgs came with a CMS SCSI II card. Like...

    My IIgs came with a CMS SCSI II card. Like previous posts state, it isn't compatible at all with the way the Apple SCSI card worked, and is kind of a pain to work with. While I was able to use it and...
  5. Replies
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    1,194

    A rubber eraser or contact cleaner would be more...

    A rubber eraser or contact cleaner would be more gentle for the contacts. Were these gold plated or tin plated?
  6. The schematic says that when R1 is cold (room...

    The schematic says that when R1 is cold (room temperature), it should read about 5 ohms. When it warms up after the power is applied, the resistance will drop.
  7. Bad solder joints can sometimes be hard to find....

    Bad solder joints can sometimes be hard to find. If looking at that feedback transformer winding doesn't pan out, might be worth it to go back and reheat those joints. Also don't forget to look for...
  8. That makes it easier for testing at least you...

    That makes it easier for testing at least you don't have to put a load on it to behave. Unfortunately in my IIgs I have a power supply made by DynaComp, so I can't go about looking to reverse...
  9. Found this Apple document for older switched...

    Found this Apple document for older switched power supplies, it has good information about switched mode power supply circuits, but won't answer your questions directly....
  10. If it isn't blowing the fuse, then maybe it is...

    If it isn't blowing the fuse, then maybe it is shutting down due to an overvoltage or overcurrent regulation. Does it shutdown if you don't have any cards in the slots? Do you have an oscilloscope...
  11. I've used a toothed drive belt from SDP/SI in a...

    I've used a toothed drive belt from SDP/SI in a flipped configuration to replace a stretched drive belt on an 8" CDC floppy drive in an HP 9895A successfully. Due to the slightly larger belt length,...
  12. I found a field change notices PDF at...

    I found a field change notices PDF at https://www.hartetechnologies.com/manuals/Northstar/North%20Star%20Field%20Change%20Notices.pdf that contains a description of a failing capacitor on the video...
  13. Then keep a ground clip attached to that lead to...

    Then keep a ground clip attached to that lead to keep the HV capacitor from recharging due to dielectric absorption.
  14. The issue is probably in the video drive...

    The issue is probably in the video drive circuitry, or possibly the video controller. Do you know if there are schematics available for your unit? I've not used a Northstar computer since 1980, so...
  15. The glow will be near the end of the neck of the...

    The glow will be near the end of the neck of the CRT close to where the wire harness attaches to the rear of the CRT neck. If you can't see in through air ventilation slots, you will need to remove...
  16. Are the brightness and contrast (if any) controls...

    Are the brightness and contrast (if any) controls set mid-position? Can you tell if the CRT cathode heater is glowing? The "high pitched scream" sound - do you think this is not the normal CRT whine?...
  17. That behavior is terrible, and the developers who...

    That behavior is terrible, and the developers who wrote that code should be strung up.

    I had something similar happen at my last job with a firmware update on some IBM servers being used as GPFS...
  18. Replies
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    915

    I've used a V5 SCSI2SD attached to my 4000/60...

    I've used a V5 SCSI2SD attached to my 4000/60 without problem, as well as various other SCSI-2 HD.
  19. I agree, you did a really nice job with that...

    I agree, you did a really nice job with that repair. While working on it, did you get any hint that the repaired part isn't bonded strongly to the original plastic and might pop off if it gets bumped?
  20. Replies
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    1,526

    The 527N may be a Signetics voltage comparator...

    The 527N may be a Signetics voltage comparator chip. My guess with the 155 decoder and the 244 buffer it may provide a crude voltage level detection capability.
  21. Replies
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    496

    I haven't needed to replace it on mine. Do you...

    I haven't needed to replace it on mine. Do you mean there are four terminals on the switch? I don't have access to the schematics of the power supply, but it sounds like it could be a double pole...
  22. Replies
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    2,676

    I replaced the belt on the one CDC 8" floppy...

    I replaced the belt on the one CDC 8" floppy drive in my HP 9895A successfully with a reversed toothed drive belt. I ordered them from Stock Drive Products (SDP/SI), the part number is A 6B16-265012,...
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    1,339

    Definitely the band saw. Very useful to build...

    Definitely the band saw. Very useful to build all the shelving you'll need to store that haul!
  24. Replies
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    298

    It appears that a 2N469 is a low voltage...

    It appears that a 2N469 is a low voltage germanium transistor, not a power transistor.
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    Do you have an oscilloscope or frequency counter?...

    Do you have an oscilloscope or frequency counter? You could attach that to the HSYNC and VSYNC outputs and determine what timing your monitor will need to support.
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