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. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    'click' FOOM!
    Oh well, at least you've got a spare...
     
  2. W7UUU

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

    haha! Well, it's not about that for me. Yes, I do have a 100% working SB-650 "spare unit" as has been posted. Yep - it works great. Yawn :) (And of course thanks to Glen K9STH for the nice stickers to label the IBM RG-62 24" coax cables that I made up to make it run on the SB-301 - both units are on the bench all the time to use as my test bed)

    Consider:

    1. I don't need a digital readout on an SB-301 receiver .... at all! The analog dial is more than adequate.

    2. This unit was given to me free - with the donor/original builder lurking on every post. I don't want to let him down. (He's very "internet shy" and doesn't want to post and I respect that)

    3. This SB-650 has taken on a life of its own after a very brutal storage for 2 decades, with continuous water damage - it will not defeat me if I can help it.

    This project has become the biggest challenge I've ever tackled in a ham radio restoration - I can't really picture more of a basket case - rotted PCB, rotted-out chips, very low-grade PCB to start with. I've repaired somewhere around 20 copper traces with new copper tape (which is AMAZING! Bought this huge roll on Amazon for $7 from China [LINK] and it's simply the best trace-repair tape I've ever used, hands down)

    I turned the corner with Jim's suggestion for how in the hell to get the "bottom side pins" soldered. I can now see the light at the end - just keep it slow, mellow, Zen "when wash dishes just wash dishes" thinking... and I now have THREE Nixie "Sockets" built, paired with their respective 7441 driver sockets - all tested 100%.

    So you see - it's just much much more than "what's my exact frequency? Gosh I wish I had a digital display!" :)

    Keep following Chris - I appreciate the support.

    It helps keep me young at heart trying to work through challenges like this.

    Dave
    W7UUU
     
    Last edited: Aug 20, 2016
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  3. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Of course I mean no ill will! This project has been fun and a learning experience for all.
    Bed time on yeast coast...
     
  4. W7UUU

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

    Better get to bread :D:D

    Thanks for all the input, Chris. Have a great weekend

    Dave
    W7UUU
     
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  5. W7UUU

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

    For the record, on the "working unit" 650, they (the controls) pretty much need to be maxxed - despite having perfect 24" RG-62 IBM-brand 92-Ohm coax cable jumpers.... I actually find the "working unit" is somewhat heat sensitive.... they warn of that in the manual actually "don't place on the transmitter" - it can go pretty squirrelly if left on for hours in the hot radio room / shop.

    I'll be curious how the "restoration unit" will work in that regard... [see what I did there?! :rolleyes:]

    Dave
    W7UUU
     
    Last edited: Aug 20, 2016
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  6. N2EY

    N2EY Premium Subscriber QRZ Page



    You're welcome, Dave. Glad to be able to contribute in some small way.


    Who, me?



    Indeed!


    Not that you need more work, but consider the following:

    Those pin jacks are very close together and there's only air between them.

    If it were me - and it isn't - I'd think about making up some sort of divider out of insulating material. Something like the divider assembly found in old-fashioned metal ice cube trays.

    I'd take something such as an old manila folder and cut it into strips, then make an assembly that would keep all the pins separate, and slide it in between the pins before inserting the Nixie tube.

    Another way to get the same result would be short pieces of insulated (heatshrink?) tubing of just the right diameter, slipped over every other pin.

    The pattern would look like this:

    oOoOoO
    OoOoOo

    where the capitals are pins with the shrink tubing and the lower case the pins without.

    All this would be done after all the soldering is finished, of course.

    Probably not necessary but....


    Nicely done and good luck!

    73 de Jim, N2EY
     
  7. W7UUU

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

    Another really good idea! I was indeed concerned about the proximity of the pins - they are very close, and due to the degradation of the pads and traces, not perfectly straight. I actually worried about one day selling this unit and shipping it - would the pins short from a hard bump in a USPS truck?!

    I like the heat-shrink solution - easy enough to do, and if I use your idea of every-other-pin there's enough space in between to make it all fit.

    Dave
    W7UUU
     
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  8. W7UUU

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

    Heat shrink won't work, unfortunately. Certainly in theory but did you ever have a pair of teeth you just couldn't get the floss between? It's like that :) As long as the pins are close to "where they ought to be" it works. But where they're slightly slanted, no dice. I don't dare try to reheat / resolder any of them just for that.

    So now I'll try this:

    Slips of thin paper (index card?) between rows - 5 small rectangles. Then cut a larger piece of heat shrink, large enough to go all the way around the "socket" and keep the paper in place - then finish with a little dot of glue on each piece.

    Off to try that now. Photo below is before I gave up on the shrink tube. SUPER touchy to get the pieces on the tighter pins. 1-2016-08-20 12.25.24.jpg

    Dave
    W7UUU
     
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  9. W7UUU

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

    Bingo!

    Much easier than the previous attempt! Once I get all the "sockets" built, and each double-tested after doing the paper/wrap application, I'll put a drop of Elmer's glue in each little pocket (using Elmer's just in case one day someone wanted to repair something). That should make them solid as a rock I should think.

    Dave
    W7UUU


    1-Shrink Socket.jpg 2-Shrink Socket  2.jpg
     
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  10. W7UUU

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

    Three down! Just checked continuity on all 12 pins on all 3 sockets = still 100%. But I won't do the glue drops until all 6 sockets are complete, just in case. It would be my luck that something would break on one of them, but only after the glue had dried.

    They came out pretty nice I have to say. Granted, it's "electronics only its mother could love" but I think they're beautiful :)

    Dave
    W7UUU


    1-sockets done.jpg
     
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