KWM-2 in rough shape

Discussion in '"Boat Anchor" & Classic Equipment' started by KK6IYM, Aug 6, 2017.

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  1. KK6IYM

    KK6IYM Ham Member QRZ Page

    The answer came to me in a dream. K3 was not functioning. K3 is the antenna relay inside the PA cage. I hoped for a simple solution. Then I woke up. K3 was not activating when the transceiver was placed in transmit. After taking the cage off and gaining access to K3, it was determined that the coil is open. This is an electrical condition known quite simply as "a bummer." I have now removed and disassembled the relay. I can find no obvious break or damage to the winding--which is very fine wire, coated with varnish, and of a specific resistance so that it matches the resistance of K4. K4 is in parallel with K3 and they must match approximately, so that they both activate together. This means the project is on hold until I can come up with a replacement relay. I have the other Peruvian KWM2 which is starting to look more and more like it will be a donor unit--although I am not there yet. I am also searching for a replacement relay from other sources--the usual suspects--eBay, Mouser, etc.

  2. W9GB

    W9GB Ham Member QRZ Page

    Collins KWM-2(A) HF Transceiver
    Modification of the Relays
    Mauro, IV3UVW

    Potter & Brumfield KR2565-1 Open Relay : K3, Antenna Relay in KWM-2.
    DPDT, 115 VDC coil

    4-Star Electronics states they have 13 pieces, in stock.

    Bob Grinnell at Surplus Sales wants $85 for his NOS Collins part.

    TE Connectivity - Potter and Brumfield
    KRPA Series : General Purpose, Panel / Plug-in Relay
    Last edited: Sep 2, 2017
  3. KK6IYM

    KK6IYM Ham Member QRZ Page

    Thanks, GB. The $85 replacement was available on eBay for $50--so I bought it. I would love to find one from Mouser for $15--just because I want lower cost parts for the future and as an option for others faced with the same issue. The part is listed as having a 115VDC coil with 10K resistance. The operating voltage is about 275VDC. There are a number of DPDT relays rated at 9 to 10K at Mouser for 110VDC and 9 to 10K coils. I am half tempted to try one of them to see if they would work. They are quite a bit cheaper. What about an AC coil relay? Why do they differentiate the two types of voltage for the coils?

  4. KK6IYM

    KK6IYM Ham Member QRZ Page

    I also ordered a Panasonic relay #HL2HDC110VF from Mouser for $20 including tax and shipping. I will be interested to see if it will work as well as the $55 relay from eBay.

  5. K9STH

    K9STH Ham Member QRZ Page


    You are a couple of days late! I sold one of the KWM-2- series antenna relays for $25.00 earlier this week! Posted the parts on both of the Collins reflectors!

    Glen, K9STH
  6. KK6IYM

    KK6IYM Ham Member QRZ Page

    Thanks, Glen. I win some and I lose some. The pendulum swings both ways. I am just glad I found the part. Of course, getting it back in place will not be easy.

  7. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Hi Norm,
    Running a relay with an AC rated coil at DC (or vice versa) will usually cause problems, some of which can be mitigated depending on the circumstances. Here's an interesting paper from Tyco (P&B).

    This is funny and true! Your sleeping brain sorts through the day's junk and tosses out the garbage. Hopefully, what's left is the good stuff! :)
    Last edited: Sep 3, 2017
  8. KK6IYM

    KK6IYM Ham Member QRZ Page

    Thanks, Chris. Good info in that paper on relays. Before plugging in my new relay, I am going to have to figure what the current draw and voltage will be and see if I am set up for proper functioning. The $55 relay appears to be an exact replacement. The $20 relay has similar parameters, but I will need to see if it indeed matches.

    KD2ACO likes this.
  9. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    It's fun to poke around and find tidbits. I knew about the Mylar tape trick but not some of the other details.

    You're helping me learn stuff by looking for answers! Nice thread.
    Last edited: Sep 4, 2017
  10. KK6IYM

    KK6IYM Ham Member QRZ Page

    Here are the photos:
    1.) New PA neutralization upgrade
    2.) Rear of the chassis showing the condition of the old RF output jack (NB jack was used as the RF out)
    3.) Middle right under the ceramic disc is the old Carrier Balance pot with part of the carbon core hanging out where the contacts are connected
    4.) The site of a new K3 relay
    5.) Rear of the chassis with a new RF output jack. I figured as long as I was running a new shielded RF cable to the relay, I should fix the rear jack.

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