Assembling a Heathkit HW-99

Discussion in 'Homebrew and Kit Projects' started by N5OLA, Jul 31, 2019.

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  1. W9GB

    W9GB Ham Member QRZ Page

    Yes ... heard he lost his job.
    My request to borrow the pristine PC boards for a GERBER Scan ... not a cheap process.
    I was sent a Color Xerox copy ...
  2. W7UUU

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

  3. N2EY

    N2EY Ham Member QRZ Page

    N5OLA and W7UUU like this.
  4. N2EY

    N2EY Ham Member QRZ Page

    Here's the topper:

    The whole "Heathkit that never was" caper was laid out right here on the 'zed, in plain sight, back in 2014 - less than a year before it went public.

    Check out posts #13, #22, #24 and #26. Also note the references to the HC-10 project.

    And this earlier thread, which also discussed the idea:
    W7UUU likes this.
  5. W9GB

    W9GB Ham Member QRZ Page

    DO NOT START Building this kit,
    UNTIL you have the NPO capacitors (noted by W9RAS below) for a Stable VFO.
    AVX and KEMET are quality mfg., but Values may be an issue for thru-hole.
    Surface mount would be challenging to add for a beginner kit builder.

    KEMET at DigiKey

    Robert Sumpton, W9RAS worked at Heathkit ... and features videos on many of the kits from his era.
    He wrote a review of the Heathkit HW-99 at on July 20, 2014
    Good details on his experience in repairing / restoring,
    especially the Critical Selection of NPO capacitors for a STABLE VFO,

    He covered the HW-99 on YouTube in July 2014

    VFO Stability Issue demonstrated with process to resolve

    Nostalgic Kits Central : HW-99
    Last edited: Aug 7, 2019
  6. N5OLA

    N5OLA XML Subscriber QRZ Page

    Thanks -- and yes, I've been in touch with Robert about this. Hayseed Hamfest is trying to find those caps for me. Gonna be a really fun build.
  7. N7EKU

    N7EKU Ham Member QRZ Page


    Seems like a lot of trouble when the main problem with the drift seems to be the main VFO inductor. I would just change it to a nice stable one wound on a powered iron toroid core.


  8. AB2YC

    AB2YC Premium Subscriber QRZ Page

    I would go through it and replace all the electrolytic caps and any carbon comp resistors as well.

    I have an un-built HR-1680 here that I plan on going through and replace those parts before I start construction
  9. N5OLA

    N5OLA XML Subscriber QRZ Page

    Wow, that will be a fun build. Yes, I am replacing all the electrolytics and testing the resistors for variances. Most of the latter were within range. Just began the build and it's such a nice feeling to open those little brown paper bags of parts, untouched for 30 years.
  10. N5OLA

    N5OLA XML Subscriber QRZ Page

    W9GB: Bob told me in an email that NPO won't work, they must be temp controlled N75 caps. "N75 that means the capacity of these moves in a negative direction 75 parts per million to compensate for the expansion of the VFO coil with heat to reduce VFO drift." DigiKey doesn't have these and they seem to be disappearing from the market. Hayseed Hamfest, ditto. So the search is on!

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