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Re: [CQ-Contest] Switching Power Supplies

To: Barry W2UP <w2up.co@gmail.com>, CQ Contest <cq-contest@contesting.com>
Subject: Re: [CQ-Contest] Switching Power Supplies
From: K9MA <k9ma@sdellington.us>
Date: Wed, 13 Nov 2024 19:34:41 -0600
List-post: <mailto:cq-contest@contesting.com>
OK, Barry asked me for the resistor value, so I had to look it up.

73,
Scott K9MA

On 11/13/2024 6:41 PM, Barry W2UP wrote:
Tnx!  I had a feeling you didn't include the value for a reason  :-)

73,
Barry W2UP

On Wed, Nov 13, 2024 at 5:10 PM K9MA <k9ma@sdellington.us> wrote:

    I was afraid someone would ask that! According to my 2011 notes,
    it was 50 Ohms, and dissipates about 0.5 W. I'd use at least a 2 W
    resistor.  That runs a K3, K4, or IC-7610 in receive mode without
    switching to full speed. (One radio at a time, maybe two.) If you
    want to experiment, use the smallest resistance which reduces the
    noise to an acceptable level.

    73,
    Scott K9MA



    On 11/13/2024 5:22 PM, Barry W2UP wrote:
    Scott,

    What value resistor?

    Tnx,
    Barry W2UP

    On Wed, Nov 13, 2024 at 4:17 PM K9MA <k9ma@sdellington.us> wrote:

        Sounds like the fan of the 1235P-M works the same way as that
        of the
        1235M, so the resistor mod should work.

        73,
        Scott K9MA

        On 11/13/2024 12:41 PM, Steve Dyer W1SRD via CQ-Contest wrote:
        > It's not variable speed, but on demand. When it turns on
        it's full on.
        > Must be something about the pitch of that sized fan that
        annoys me.
        > Maybe all the years working on 1U server farms at data centers.
        > 73,
        > Steve
        > W1SRD
        >
        >
        > On 11/13/2024 9:47 AM, K9MA wrote:
        >> I did a very simple mod to 1235M:  A resistor in parallel
        with the
        >> thermostat. This causes the fan to run continuously at low
        speed,
        >> rather than cycling when demand is low. The fan runs at
        full speed
        >> only during times when I'm transmitting a lot, when the
        fans in the
        >> radio and amplifier drown it out.
        >>
        >> The 1235P-M may be different, but I doubt it has a
        variable speed
        >> fan, or this mod wouldn't be necessary.
        >>
        >> 73,
        >>
        >> Scott K9MA
        >>
        >>
        >>
        >> On 11/12/2024 8:00 PM, Steve Dyer W1SRD via CQ-Contest wrote:
        >>> My only gripe with the 1235P-M is the fan noise. Good PS
        otherwise.
        >>> 73,
        >>> Steve
        >>
        >>
        >


-- Scott K9MA

    k9ma@sdellington.us


--
Scott  K9MA

k9ma@sdellington.us
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