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

    HUGE thanks to my friend Ron, KC7J, for donating his SB-650 to me for my K1T commemorative station to celebrate the 70th anniversary of the first electronic Heathkit (October 1947) in October 2017. I can't believe my good fortune to acquire one of the rarest of Heathkit boxes (I also found the other ultra-rare box, the SB-640 remote LMO that will get restored oon - thanks to Brian KB4MNG - traded a nice R4 receiver for it).

    Ron built the SB-650 new 40 years ago, and paired it with an SB-101. It worked perfectly when put into storage, which is always a good omen. But it was taken out of its case at some point, put on a shelf, and the roof leaked. So it had a pretty extensive water damage - but just a "drip drip drip" sort of thing.

    My game plan is:

    1. Remove all the chips - most of them have rusted pins
    2. Remove the PCB for a thorough cleaning - water, windex, flux remover - the works.
    3. Check all of the sockets for continuity from top-side to bottom-side. I plan to use actual old chips with DeOxit to work each socket and all its pins to insure 100% continuity top to bottom. Any sockets that I can't get perfect continuity will have to be replaced
    4. Find replacements for ALL of the 74-series chips. I have a zillion, my son has a zillion - and 74-series TTL chips can still be had easily all over the internet.
    5. Do the same for all 6 display tube sockets
    6. Remove and de-rust the transformer - repaint it black
    7. Replace the three capacitors
    8. Check all the 1/2-watt resistors for value changes
    9. Restore the "silver line" in the bezel - I think I know how I'm going to do this....
    10. Do resistance checks per the manual (thanks to K0JKJ for posting the link - I just couldn't find it!!)
    11. POWER UP for the first time in decades!!

    Any critical step I'm missing?

    Will be paired with my SB-301/SB-401 rig for 80-10m CW during K1T

    I never in my wildest dreams for the K1T project imagined I'd be so lucky as to find not only an SB-640 LMO for the SB-101 to work split during my event, but to find an SB-650 to work on the 301???!!!

    RON - I could just hug you right now :):) If there's anything I can do for you, just let me know.

    NOTE: I can't start this restoration until I get the DX-60b running up to snuff - still working through some issues on it but I've decided the SB-650 just has to "be next" and the 610/620/640 will have to wait their turns on the bench. And I'm off to a trade show all of next week - so will be a couple of weeks before I can start to post the restoration stuff.... mods please don't close it :)

    Photos below.

    What an amazing thing.... I can't believe I actually now own an SB-650 :eek::)


    650-1.jpg 650-2.jpg 650-3.jpg 650-4.jpg 650-5.jpg 650-6.jpg
    Last edited: Jun 4, 2016
    N7ANN, KC9UDX and K7TRF like this.
  2. W7UUU

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

    So after going through the manual it appears the only thing missing is the "Light Shield" - just seems to be a little box that covers the Nixie tubes, with openings for their tops to stick out a hair for cooling I'm guessing. I should be able to fabricate that from maybe PCB material & paint it flat black. Otherwise, as far as I can tell, it's all here 100%


    light shield.JPG
  3. N2EY

    N2EY Premium Subscriber QRZ Page


    It's in the right hands now. The before-and-after pics will be ones for the books.

    The only possible dealbreaker is if the moisture destroyed the transformer. Otherwise....everything is fixable.

    The TTL may still be good but of course you want spares in order to be able to check.

    Dave, you might consider removing the board and resoldering all the connections just on general principles.

    The light shield could be made from flashing aluminum or similar thin metal. Paint it black, as you say.

    I see a red door.......

    73 de Jim, N2EY
  4. W7UUU

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

    I think you're right Jim. I've been thinking about this one a LOT. Once I get the PCB removed and evaluate its condition, I'm thinking I'll just replace all of the chip sockets. On close examination, not a single one is without flaws. The moisture damaged all of them. I doubt I can find white sockets though.... but at least really good quality plated-hole black ones.

    Same on the TTL - most look damaged pin-wise. But none are rare by any means. I have most of the chips in my shop, and the rest can be sourced easily from Asia where they still produce TTL chips.

    Either way, yes - I'll resolder all of the connections just on general principles.

    Even if the transformer were trashed, it's just voltages. IF that were the case, I'd work a mod with a rear apron connector to an external supply. I'm not too worried about that - and the "drip drip drip" over the years was on the other side of the PCB - the transformer looks pretty good.

    I feel very fortunate that the case is almost perfect, as is the face plate, bezel, and logo - all the truly irreplaceable stuff. Good idea on the flashing - I'll find something workable. Very odd that it's missing - I may ask Ron to look on the shelf where this sat all those years - maybe the original shield is still sitting there.

    Really looking forward to this project - alas, it has to wait for almost two weeks before I can start in earnest

  5. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Very cool Dave!

    Those photos take me back. My first kit project was a digital clock with nixie tubes and all those 74 series socketed chips bring back a lot of early memories. With all that rust you'll want to validate that the sockets themselves are in decent shape electrically but your plan sounds good.

    Good luck,
  6. KC9UDX

    KC9UDX Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Don't forget to paint the replacement sockets. :)
  7. W7UUU

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

    Interesting note: in reading the manual, Heathkit recommends RG-58/U cable on page 30 of the SB-650 manual, "Cable Preparation" - I thought it was supposed to be RG-62/U ??

    Anyone know why the discrepancy?

  8. W7UUU

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

    After looking at the chip sockets long and hard, I just can't bring myself to reuse them. It's a lot of work, but I'm afraid I have to desolder each and every one of them and replace them with new.

    I found a supplier from Asia on eBay with gold-plated, high quality sockets - not the cheapie Radio Shack variety. Reasonably priced - 100 pieces each of the 16-pin and the 14-pin for less than $30 total, including shipping.

    Some of the chips will be tough to get if bad - notably, the SN7441B "Nixie Driver". So I'm hoping that flavor all work - but I do have a TTL chip tester that should help Test/ID the 7441B chips, which all look excellent - gold plated pins prevented rust over all the other chips! NICE! All the other TTL chips are pretty much garden variety - and every one with only a couple exceptions have rust. I'll very likely replace them all just on principle. But I'll pop them in the tester - ya never know.

    I really wish I wasn't heading out for a week on the road - I'd love to really dig into this SB-650 right now!


    aSockets 2.jpg aSockets.jpg
    N7ANN likes this.
  9. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Those machine pin sockets look fine. Do you have a Hakko 808 desoldering station? Best 300 bucks I ever spent. You could strip those old sockets out in about 15 minutes. After that, you could easily scrub the salts and rust off of that board.
  10. W7UUU

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

    Yikes! I don't have one - I just looked it up though. I have a solder sucker or two and LOTS of solder wick :)

    I don't need to do it in 15 minutes though. One or three or five sockets removed a night is fine for me. I can still scrub the boards and re-tin - might take me a longer time, but I'm probably not going to jump for a $294 solder sucker just yet for this :)

    My old-school "Soldapullt" solder suckers work pretty well and I'm in no hurry :)

    Thanks for the idea though!

    KC9UDX likes this.

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