recap heath kit SB301

Discussion in '"Boat Anchor" & Classic Equipment' started by KB1FGC, May 25, 2021.

ad: L-HROutlet
ad: l-rl
ad: HRDLLC-2
ad: abrind-2
ad: L-Geochron
ad: L-MFJ
ad: Left-2
ad: MessiPaoloni-1
ad: Left-3
  1. KB1FGC

    KB1FGC Ham Member QRZ Page

    I was thinking of just clipping the leads on the old capacitors and soldering the new leads into the older ones.I just thought it might be easier than trying to take the solder off since most of the old leads are wrapped on pretty tight.
    Thanks
    73
    Rich
     
    Last edited: May 25, 2021
  2. W5RKL

    W5RKL Ham Member QRZ Page

    HI, rich,

    Your post is missing some information. You might want to explain in further detail what your capacitor replacement
    idea is.

    For example, are you leaving the can capacitor in place and connecting new axial lead caps to the old can capacitor
    terminals? If that's what you are saying then I do not recommend you do that. I recommend you purchase and
    install the SB-300 capacitor replacement kit from hayseedhamfest.com (see link below).

    https://hayseedhamfest.com/collections/heathkit/products/copy-of-heathkit-sb-300-re-cap-kit

    73
    Mike W5RKL
     
  3. KB1FGC

    KB1FGC Ham Member QRZ Page

    Hi Mike.I got the
    Hi Mike.I got the kits for both my SB401 and SB301 from Hayseed Hamfest.So far 4 capacitors are installed.The leads were really wrapped in and I didn't want to damage other components by over heating.I managed to get all but one of the old leads out--so far.So I am replacing all the old electrolytic caps.If I manage to get all the old solder off and get the old leads out then that's my plan.If it gets pretty tough,Then I figure to clip the old leads and join the new ones to the older ones.I was just wondering if that wasn't good pracitce.
    73
    Rich
     
  4. W5RKL

    W5RKL Ham Member QRZ Page

    Rich,

    When performing repairs, you want to do it right. This requires additional work and time but the end result will be worth it.
    I've run into can capacitors where the can's twist-locks were soldered to the mounting plate. Melt the solder on the can's
    twist-lock to remove the solder. If the solder can't be removed, use pliers to "twist" the individual twist-locks until they come
    off. Since the old capacitor will be thrown away, you don't care whether the can's twist-locks come off easy or need to be twisted
    off. Once the old can capacitor is removed, clean up the twist-lock slots of any remaining solder so the new can will easily slide onto the
    mounting plate If the mounting plate is bent, remove it and use a hammer and a flat metal surface to flatten the mounting plate then
    reinstall the plate on the chassis.

    When mounting the new can capacitor on the mounting plate, make sure you mount it with the capacitor value tabs in the same position
    as the original capacitor. This requires you to pay attention and make notes/drawings how the original capacitor value tabs were located
    BEFORE you remove the can capacitor.

    73
    Mike W5RKL
     
  5. W9GB

    W9GB Ham Member QRZ Page

    The Heathkit assembly method was to mechanical connect wire or component to the solder terminal and then Solder.
    To Remove is a Two-Step Process and REQUIRES usage of Desolder Braid or Wick,
    then remove Mechanical attachment.

    American Beauty “Dri-Wick” Desoldering Braid
    https://americanbeautytools.com/Desoldering-Braid

    MG Chemicals “Super Wick” Desoldering Wick
    https://www.mgchemicals.com/products/soldering-supplies/desoldering-braids/solder-wick/
    7BC38CAB-0ED7-4DC9-A3BA-DE65DFF1DE5A.jpeg 97152193-C8A8-490C-B278-C6C031FFE1DF.jpeg

    Liquid Solder Flux can be used for “old solder formulations” and dry joints.
     
    Last edited: May 27, 2021
  6. KB1FGC

    KB1FGC Ham Member QRZ Page

    Thanks!I'll get some of the thicker wick.Also I didn't realize the liquid flux would help with old solder.I noticed my solder wick doesn't work as well on it so maybe that's the secret-liquid flux.
    73
    Rick
     
  7. KB1FGC

    KB1FGC Ham Member QRZ Page

    Mike thanks again.I already got the caps in but the new can capicitors have smaller holes and and the terminals bend easily.But I put a slight hook in the leads.On one terminal it was so tight the leads seemed to fit well.I also did a continuity test to check.Hopefully I did OK and it won't cuase problems in the future.Yea the previous owner soldered one of the tabs in.Thanks for the extra tip that will come in handy.I didn't solder the taps as far as I can tell Heathkit didn't say to and the can seemed in pretty good.
    73
     
  8. W9GB

    W9GB Ham Member QRZ Page

    Rick -
    I prefer that weekend (shade tree) hobbyists and radio amateurs use
    an “RA” Flux solder (60/40 or 63/37 eutectic Tin/Pb), like Kester “44”.
    Use 0.031” diameter OR Smaller. 0.020” diameter is very good for surface mount (SMT)
    Kester has a good “No Lead” solder formulation in Pocket-Pak, if required.

    KESTER POCKET-PAKs : NTE now stocks and sells these useful tubes.
    https://www.nteinc.com/kester/pocket-paks.php
    19DB88BC-D378-4CC4-A26E-59CF68F51DDB.jpeg
    ==
    ROSIN FLUX is the secret sauce (Ask your local violinist).

    NOT ALL DE-SOLDERING BRAIDS are the SAME.

    1. USE a DeSoldering Wick or Braid that has been pre-treated with Rosin Flux

    2. MATCH Size (width) of the Solder Wick to the Solder Joint you are working on.

    3. USAGE TRICK, OPEN the BRAID, By Pushing the Cut End of the Braid, BACK on to itself, Toward the Roll. Some Desoldering Braids are Too Tight (and does not work).
    Small transparent Air Gaps are created in the braid.
    SOLDER will FILL those spaces (Like a Magnet) — INCREASING its Effectiveness.

    4. Liquid Solder Flux with a Pen (Felt style tip) OR Bottle with Needle Applicator,
    re-introduces Flux to the original solder joint. This makes a big difference to liquify the old solder.
    1950s and 1960s Solder used with Heathkit assembly was often the 60/40 alloy , larger diameter (0.050”) sample, provided by Heathkit (sometimes from Kester).

    5. Clean the Joint area (isopropyl alcohol - CAUTION Avoid Heat when using),
    before adding new components and then soldering.
     
    Last edited: May 28, 2021

Share This Page