HW-101 recap

Discussion in 'Radio Circuits, Repair & Performance' started by N5OLA, Aug 10, 2019.

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  1. N5OLA

    N5OLA Ham Member QRZ Page

    Hi -- I'm recapping a Heathkit HW-101. On cap C212 the negative terminal goes to ground, and it's right up against the chassis so that you can't solder it without creating a bridge from the ground portion of the board to the chassis. I have a hunch that this is okay, but wanted to clear it with wiser minds, as this is my first recap and I don't want to screw it up. Here's an xray from the manual.

    73,
    N5OLA

    upload_2019-8-10_11-30-42.png
     
  2. W7UUU

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

    You'll be just fine.

    The negative PCB path is at chassis ground. In fact, make certain that all the screws and lockwashers that hold the circuit boards to the chassis are clean and tightly bonded. One of the classic gremlins in the old Heathkit rigs with PC boards is those screws getting loose and dirty over the years, and causing intermittent ground connection issues to the ground foil on the PC board

    Dave
    W7UUU
     
    N5OLA likes this.
  3. W5RKL

    W5RKL Ham Member QRZ Page

    That's not a problem. All of the 5 board's ground to chassis connection is made
    using 3-48x3/8" machine screws, #3 internal star lock washers and 3-48 machine
    nuts. The foil edge of each board connects to the chassis through the mounting
    hardware as shown in the picture below. I suspect the chassis area below each PC
    board has years of dirt/corrosion and more than likely many of the PC board's mounting
    hardware have rusted. This affects the ground, through the mounting hardware and foil edge
    side of all the PC boards, to the chassis. When I fully restored and scratch built 2 HW-101s
    I replaced all of the PC board mounting hardware, fully restored the chassis to like new
    condition, and cleaned each PC board foil edge grounds to ensure a solid ground between
    the board and the chassis. There are 69 3-48x3/8 machine screws, 138 #3 star lock washers,
    and 69 3-48 machine nuts that are used as mounting hardware to the chassis for all 5 of the
    PC boards. Each 3-48x3/8 machine screws requires "2" #3 star lock washers.

    https://w5rkl.com/heathkit-hw-101-complete-rebuild/

    The following is a list of eBay ads that sell the 3-48x3/8 machine screws, #3 star
    lock washers, and 3-48 machine nuts.

    3-48x3/8 Machine screws (phillips head)
    eBay ad #201736232516
    Price for qty of 100 = $12.21 free shipping

    #3 lock washers
    eBay ad #201953089043
    Price for qty of 100 = $10.68 free shipping

    3-48 machine nut
    eBay ad #332346610438
    Price for qty of 100 = $6.78 free shipping

    If you don't have the complete HW-101 assembly manual, which you should have
    when performing repairs, you can download it from my website using the link
    below.

    https://w5rkl.com/wp-content/uploads/2014/04/heathkit-hw-101-manual.pdf

    upload_2019-8-10_17-21-11.png

    73
    Mike W5RKL
    https://www.w5rkl.com
     
    Last edited: Aug 11, 2019
    N4FZ and N5OLA like this.
  4. N5OLA

    N5OLA Ham Member QRZ Page

    Thanks, Mike. Just thinking out loud, but would it be just as efficient to run a jumper wire from each PCB ground to chassis? What terrorizes me about removing the boards is all the wiring that will have to come out. No rust on this unit, but I understand that they need to be well grounded.
     
  5. W7UUU

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

    Don't over-think it.

    Just make sure all the screws are tight to the chassis and to the PCB foil.

    Simple simple

    Dave
    W7UUU
     
    K7TRF, WA7PRC and N5OLA like this.
  6. K7TRF

    K7TRF Premium Subscriber QRZ Page

    As posted above you just need to make sure the PCB screws are snug and making a good electrical connection the chassis. One way is to completely remove the board but the easy way is to loosen the screws one at a time and then retighten them. That tends to scrub off oxidation between the chassis and the screw which helps assure a good electrical connection.

    If the chassis is visibly rusted or heavily oxidized it can pay to remove each screw, scrub the chassis clean with a Scotchbrite pad and then replace the PCB mounting screw against the cleaned chassis surface. This is overkill for typical rigs in decent shape without a lot of oxidation where just loosening and then retightening each screw gets the job done.
     
    N5OLA likes this.
  7. N1OOQ

    N1OOQ Ham Member QRZ Page

    Wow, 3-48 screws... dat's old school.
     
    N5OLA likes this.

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