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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 you want to do this, the next logical step is to design your own PCB and have one made. believe it or not this is quite reasonable.
    The software can be had for free...
    Besides I am sure there is a niche market for replacement PCB boards for those things.
     
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  2. N2EY

    N2EY Premium Subscriber QRZ Page



    How Mr. Carlson makes his own double-sided PC boards.
     
  3. W7UUU

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

    So noted and I plan to watch the whole thing. It's been many years since I've made a PC board - and the stuff I used back in the 70s made pretty horrible boards (Radio shack PCB kits).

    However, today at lunch, I was wound up from work crap and slipped into the shop and found my Zen With Pins. The frustrations of yesterday had to do with them snapping off when I'd try to bend them into a straighter line. But I found a technique today using a sharp "PC board pick" (pointy tool with a 90-degree bend on one end). I insert the pin in the hole, holding it down with my left hand on the PCB pick, and then with a "solder-loaded tip" on the iron, I solder the pin to the trace and use the pick to make it as straight as I can.

    It works GREAT on the pins that have a top-side trace. I did all the pins in the photo in one 1-hour session, and since I was able to align them fairly well (very delicate balance between getting "straight enough" and avoiding too much heat to ruin the delicate trace). This is very much like horseshoes - "close enough still counts". The Nixie tubes fortunately have wires for pins, so they can be made to fit.

    The best part: I did a full continuity check on every single pin, and 100% of what I did at lunch today works. I also tested for shorts - all good there as well. No, it's not pretty. FAR from pretty. But it will work and that's what counts. I believe it will be stable for many years to come as well, and once it's back in the box working (!!) no one would ever know what evil lurks.

    Done for now. No more today - I'll do more top-side pins tomorrow on the remaining 5 "sockets".

    So now the next hurdle: how to manage the pins that don't have a top-side trace. The very very low-grade "plate-through holes" are NOT plated through so I will have to find a way to maybe glue the pins in the holes on top - spot of Elmer's Glue and allow it to dry? - then flip the board to solder the trace on the bottom side.

    I look at the rest of the board and it's a total piece of cake.... if I can manage to build up these sockets like I figured out today, I should be home free once they're done.

    Good progress at lunch.... I'm pleased with what I was able to do in an hour (Note that I did not yet spray flux remover - I'll do them all at once at the end. My wife hates the smell so I will wait until they're all done to clean the mess - since we share the same shack space)


    Tonight I'll maybe start on the Ameco AC-1 :)

    Dave
    W7UUU

    1-2016-08-16 13.52.33.jpg 2-2016-08-16 13.52.20.jpg
     
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  4. N2EY

    N2EY Premium Subscriber QRZ Page

    NICE! Congrats! Particularly the Zen part.

    Or Krazy Glue.

    Plus the delicate board should be stressed as little as possible. One flux remover application is better than several.

    Excellent!

    We demand pictures!

    73 de Jim N2EY
     
  5. W7UUU

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

    Thanks.... "when wash dishes, just wash dishes" :)



    I considered that. But it's much more of a commitment - if for any reason I'd need to pull the pin, I'd be in a tough spot... trying to undo the Krazy Glue could cause more damage than removing Elmer's Glue - which is water soluble - I can actually remove the glue fairly easily after soldering the bottom side. See what I mean?



    GREAT point! I had not thought of that - but as with my point about the glue, anything I can do to make this poor tired old PC board have a happy "last chance at life" there's absolutely no need to worry about rosin overflow - I'll just forgo it altogether probably. It's purely cosmetic in an essentially low-voltage circuit, right? NO ONE WILL EVER see the bottom of this board again - until the day it's stripped for parts. Who cares?!



    You know me.... :rolleyes:

    Dave
    W7UUU
     
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  6. N2EY

    N2EY Premium Subscriber QRZ Page

    Exactly.

    Good point. Elmer's dries slowly, but that's not the issue.

    Here's another trick:

    Find a paper clip whose wire is the same diameter as the Nixie tube pins. Unbend it, then make a U piece whose sides are exactly the right spacing. Use it as a jig with one side in a top-soldered pin and the other in a bottom soldered pin, so the soldering job can be done.

    One wash and done.....

    It's going to be legen.....

    (wait for it)

    dary!


    73 de jim, N2EY
     
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  7. W7UUU

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

    Excellent idea! I'm leaving the office early today and will give that a try straight away. Frankly, it would help with the top-side pins just as much. I still have 66 more pins to install :eek: to finish the Nixie sockets

    will post up results later

    Dave
    W7UUU
     
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  8. W7UUU

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

    Sometimes the simplest of ideas can be the most amazing! I just took a 15 minute work break and in that time, got SIXTEEN more pins installed!! Just using snipped off wires from a few sacrificial electrolytic caps. It works AMAZINGLY WELL. I did all sixteen at one time!! Just took minutes.

    All check good for continuity - and thankfully, Heathkit ran only ONE trace to a pin, either on top or on the bottom - never to the same pin on both sides. So I was very easily able to check continuity on all twenty four installed pins.

    Amazing - thank you Jim for the most effective simplest solution to a very difficult problem I think I've ever had!
    I did try to insert a Nixie tube - that's going to take some work too - but it's just a matter of very patiently putting very slight bends on each wire one at a time to match the not-perfect alignment of the "socket". But I can see that I can do it - so once the board is otherwise fully populated and traces repaired, I can carefully insert all the tubes before putting the board back in the case - it would be extremely hard to insert the tubes with the board in place.

    Anyway, thanks again Jim for a truly brilliant suggestion. Now don't let it go to your head... :rolleyes::D

    Dave
    W7UUU


    1-wires-1.jpg 2-wires-2.jpg
     
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  9. W7UUU

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

    I'm now at 50% of the Nixie Tube sockets being installed and all tested using your clever idea!! Every trace checks out, no shorts between pins - almost all are solid in place - there are a few "loose teeth" but electrically they are excellent and once the tube is finally installed the 2 or 3 slightly loose pins will be fully stable.

    Going to take a break now - no more pins tonight - my back is KILLING me from bending over this PCB. It's really exacting work - considering that I have to use copper tape to repair traces as I go long (ALL are on the bottom - 99% of the top traces are in very good shape).

    Pretty ugly on the bottom side, but it will work.

    Once all 6 "sockets" are finished, I'm going to install the 7441 driver chip sockets - that way I can fully check continuity from driver to Nixie socket to be certain all of those paths - the very worst paths on the board - are clear.

    Dave
    W7UUU

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  10. W7UUU

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

    Starting to make some real progress now.... I installed the first three new 7441 HV Driver chip sockets (painted white to match the originals, and of course the machined pin sockets were masked with old junk chips during painting to protect the sockets - only the exterior of the sockets was painted).

    I checked every single Nixie pin to every single related 7441 and have confirmed 100% connectivity, no shorts. I made up a couple of jumpers using more of the machined pins that made it very easy to check continuity quickly.

    Tomorrow I'm going to start on the Ameco AC-1 construction, but hopefully find more time to finish the next three Nixie "sockets" in the SB-650.... or even just one.

    Looking at the rest of the board, after getting these blasted "sockets" built, it will be a cake-walk by comparison.

    I have decided though that I will power up the board outside the case just to test just for basic "zero on the Nixies", when the board is all back together with all new parts. Now granted, the 40673 preamp circuits will I'm sure prove their own challenge - but one bridge at a time.
    A month ago, after the heartbreak of finding out what an utter mess this PCB was, I never thought I'd be this far even.... maybe in another month, I'll have "Nixie Action". I've tested each and every tube in the "working unit" and they are all good - and 100% of the chips are good - and all the discrete parts are new - with just a few notable exceptions (transformer, precision resistors of really odd values, 7441 Nixie driver chips - but all of these exceptions have been tested).

    And I now have THREE working Nixie Tube "sockets" and three new 16-pin DIP sockets for the drivers - and it all tests 100% for the work I accomplished.

    I don't want to jinx anything.... but read between the lines - this just may end up working

    Dave
    W7UUU


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