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. AF6LJ

    AF6LJ Ham Member QRZ Page

    If that doesn't work out you might have to rinse it out and use polyester rosin.
     
  2. KE0EFX

    KE0EFX Ham Member QRZ Page

    I was just trying to help you avoid another DUH! moment...that's all.
     
  3. W7UUU

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

    Thanks Sue... I sure hope I didn't screw up with the Elmer's - that's one question I should have asked first. But I've done pretty extensive Googling, and PVA appears to be a very good dialectric as long as it's dry, of course. It's only 170 volts with pretty good spacing between pins. I'll certainly know as soon as I power up - if every tube is a blur, I'll know that the glue is conducting and not insulating :)

    Fingers crossed that won't be the case. And if the glue breaks down, I'll just trash the thing at that point. There's absolutely no way these sockets could be rebuilt a second time.

    I think what I'm going to do is build up the HV supply first thing - nothing more. Then install all 6 10k limiting resistors. They I can simply take a wire attached to PCB ground and working from the 7441 socket, ground the number-element pins on the 7441 socket pins and light up every Nixie number one at a time - maybe leave one running for a few days to see if the Elmer's breaks down or not.

    That way I won't waste 150 parts and hours of time building a board that won't work :)

    Dave
    W7UUU
     
    AF6LJ likes this.
  4. AF6LJ

    AF6LJ Ham Member QRZ Page

    I figured you had done some research...
    Besides this is simple enough to test with a power supply an ammeter and some dry glue with pins in it.
     
  5. W7UUU

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

    Good idea - much simpler.

    And no, I did absolutely ZERO research LOL! I can very scatterbrained sometimes, no matter how meticulous I might be along the way. I'll do that test tonight and report back.

    Dave
    W7UUU
     
    AF6LJ likes this.
  6. W7UUU

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


    Haha! I get it now :) Yeah, per my post right above this one - I really need more sticky notes :)

    Dave
    W7UUU
     
  7. AF6LJ

    AF6LJ Ham Member QRZ Page

    There is a person on our club repeater who has said "Sue has to make sure everything is perfect before she lifts a finger to do anything." Funny thing is....... He is almost right. :)
    Took me over a year to decide what to put up for a 2-meter antenna.
     
  8. N2EY

    N2EY Premium Subscriber QRZ Page

    I'm going to make a prediction:

    I predict there will be no problem at all, once the glue is dry.

    73 de Jim, N2EY
     
  9. W7UUU

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

    Yep - that's my feeling too. Everything I've read about PVA is it's a fine dialectric. But good science dictates: I just poured a little blob in a plastic spoon to dry and hopefully by tonight it will be dry enough to test. I'll just lash up the 170v transformer tonight and (assuming the glue is fully dry) just confirm that no current flows through the dried glue.

    Dave
    W7UUU
     
  10. N2EY

    N2EY Premium Subscriber QRZ Page

    Actually, good engineering* would be to simply install the 10K resistors on one digit, apply 170 volts, and test each number by grounding. That way, you are testing the actual application.

    Note that because they are Nixies the insulation does not have to be perfect. If it is good enough that leakage is below the striking voltage, you'll be OK.

    S0....has this discussion become a dialectic about dielectrics?

    73 de Jim, N2EY

    * "Scientists dream of doing great things. Engineers do them." - Werner Von Braun
    "Science is about knowing. Engineering is about doing." - Henry Petroski
    "One man's magic is another man's engineering. Supernatural is a null word." - Robert A. Heinlein
     
    Last edited: Sep 2, 2016

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