Manna from Heaven: Donated Heathkit SB-650 Digital Display for K1T

Discussion in '"Boat Anchor" & Classic Equipment' started by W7UUU, Jun 4, 2016.

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  1. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    LAST SOCKET DONE!!!

    V2 was the last Nixie socket to be completed. Interesting to look at the progression - V1 (farthest on the right, the Hz tube) was the first I did... V2, right to the left of it, is so much better! But that's just aesthetics.... practice makes perfect indeed!!

    But I worked up a quick pin-to-pin "quick test" diagram, and carefully checked EVERY SINGLE SOCKET... V6 threw me off for a minute on one pin, until I realized that the "zero" of V6 doesn't connect to anything LOL! DUH!

    ALL 6 sockets check 100% continuity to their 7441 driver sockets.... that's really awesome! All the trace repairs work - all the pins work - it's all coming together, at least in that part of the circuit.

    Last step to call the sockets "done" is to "pot them" with slightly dilute glue, to hold all the pins and spacers together.

    Taking a dinner break now - but nice stopping point.

    Dave
    W7UUU

    1-last-socket-1.jpg 2-last-socket-2.jpg 3-last-socket-3.jpg
     
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  2. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    It occurred to me, while "handing out sockets", why not give V7 (KHz NE-2H) and V8 (Mister Decimal Point!) their own sockets - should (I manage to get this thing to work!!) their future owners face a dead Neon bulb, they don't have to remove the main PCB, which is a LOT of work? Why not!! Heathkit really should have had some sort of socket for those, given how hard they are to replace otherwise....

    Note that the NE-2 bulbs for the photo are NOT the "final installation version" but rather plain old NE-2 bulbs from the junkbox. I have "proper" NE-2H bulbs ready to go, with shrink-tube insulated legs for the final install. These were "just for looks" in the photo, to show the idea.

    Dave
    W7UUU


    1-2016-09-01 20.18.38.jpg 2-NE-2 Socket 1.jpg 3-NE-2 Socket 2.jpg 4-NE-2 Socket 3.jpg
     
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  3. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    After one final continuity check, pin by pin, from the Nixie "socket" to its associated 7441 driver socket, and it was time for the potting - a pretty "final step" - not easy to undo (nor impossible either - just not easy!)...

    I diluted Elmer's Glue (OK ... a generic version :p) about 1/3 H2O to glue, and injected as many cavities as I could under the magnifier - slow and steady but I got them all. All the card-file paper divider/insulators should now nicely bond over the next few days, and really snug things up.

    I plan to do some sort of similar thing to the underside, after a week-long cure of the Elmer's glue (since it was diluted, will take much longer to cure)... probably a similar treatment on the foil side, using a "box it in" form I'll make up for the task - to save all the dozen or so foil repairs.

    But for now? It's really looking up! I really feel like I know a Heathkit SB-650 at a pretty organic level at this point....

    Photos below: POTTED SOCKETS!!! (tested 100% for continuity) = DONE!!!!! Can you believe it? If you're just tuning in, scroll back to the beginning!! :)

    Dave
    W7UUU

    1-potted-1.jpg 2-Potted-2.jpg
     
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  4. AF6LJ

    AF6LJ Ham Member QRZ Page

    Looks good Dave :)
     
  5. N2EY

    N2EY Premium Subscriber QRZ Page

    Most excellent, Dave. What a journey!

    The moment of truth approaches.....when the thing is powered up.
     
  6. K7JEM

    K7JEM Ham Member QRZ Page

    Have you tested the dried Elmers glue for continuity or voltage breakdown? Because of the high voltage and high impedance of the source, it might be a concern. But maybe not.
     
  7. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Good point I had not considered.... I doubt it will be a problem though. Damn well better NOT be a problem LOL! :)

    The reality is, without a potting compound of some sort, the structural integrity of the Nixie pins wouldn't be very stable. The trace damage was such that many of the pins were "wobbly". So it's one of those things where there isn't any other options. It will either work or it won't but at this juncture, I have no choice but to keep on keeping on with the project

    Thanks for pointing that out. It led me to learn that white glue like Elmer's etc. uses Polyvinyl Acetate (PVA) as the primary "glue" ingredient, and it in fact appears to be an electrical insulator so long as not mixed with other stuff like carbon or other conductors - which white glue doesn't have.

    So I should be fine...

    Dave
    W7UUU
     
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  8. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Thanks Sue!

    Won't be too long now... compared to restoring the Nixie sockets, the rest is just through-hole parts. There are maybe 10 more trace repairs to do along the way, but they're all in "wide open spaces" - I plan to just hit the "start here" in the assembly manual and start from the top. I had notions of building the power supply first, to have testing voltages - but knowing I have 100% continuity from the 7441 sockets to every pin on every Nixie (excepting of course the "zero" on V6) is all I really need to know.

    I fully expect to have challenges on the 3 analog amplifier sections - but once it's all built back up, I can easily test the master oscillator and divide-by counters on the scope, and inject square waves into the TTL counting stages and determine if all the DCU chains are working out to the Nixies - and I'm fully confident all of the digital stuff will work.

    I don't have all that much confidence in the 40673 circuits... but we'll see, won't we :)

    Dave
    W7UUU
     
  9. KE0EFX

    KE0EFX Ham Member QRZ Page

    This has been a great project to follow along with and I'm learning a bunch, not only from you, Dave, but from all the suggestions and comments you get from others! Thanks for taking us all on this ride! By the way, you take some super photos of the progress; I don't think I could see it all that clearly in person. :) Maybe you should make some post-it notes at several strategic locations: "zero" on V6 :rolleyes:
     
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  10. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Thanks. Not sure I understand that last sentence though...

    The pics are just from my Samsung Galaxy 6s - takes better photos than my Nikon DSLR!

    Dave
    W7UUU
     

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