[SADXA] RFI

[Wes]

Hi Bill,

Thanks for your reply.  Your mention of a schematic in the box jogged my memory 
and I've discovered a weathered copy of a schematic that I removed from the box 
years ago and filed away for safekeeping.  It's hard to read but I'm scanning it 
and trying to improve readability.

We'll see if it helps.

Thanks again!

Wes


On 7/8/2020 8:56 AM, W7EXG (Bill) wrote:
> Hi Wes,
>
> Good sleuthing!!
>
> I have 2 American Standards that are normally running intermittently at this
> time. They were installed new about 2008. I have not experienced such noise.
> I suspect there is some type of failure with the relay, or relay circuitry
> when unit is in the off mode.
>
> I will look and see if, by chance, there is a schematic glued of tucked into
> the back of the unit somewhere.
>
> However, it might be a mute point, if my model does not match your model?
>
> Just a FYI in case any of this might help.
>
> Bill W7EXG
>
>
> -----Original Message-----
> From: sadxa-bounces at mailman.qth.net [mailto:sadxa-bounces at mailman.qth.net]
> On Behalf Of Wes
> Sent: Tuesday, July 07, 2020 4:56 PM
> To: SADXA
> Subject: [SADXA] RFI
>
> I haven't been too active lately, so I can't pinpoint when this started but
> I
> discovered it on Field Day when I was plagued with an intermittent noise
> that
> made me give up.  Trico has been quite good about working these issues, but
> the
> intermittent nature didn't bode well for it happening when they were
> looking.
> So I did some sleuthing of my own.  My tribander is about 120 feet from the
> house and my power line is to the west of it.  The house is NE of the
> tower.
> The noise actually went down when pointed west but peaked when pointed at
> the
> house.  I could hear it everywhere from 160 to 6 meters on my Sony
> ICF-SW7600,
> even inside the house when it was on.  The problem was it was off more than
> on.
>
> I had a previous issue with my Internet system causing a problem when the
> Ethernet cable hooked to the rooftop Wi-Max receiver wasn't plugged in
> completely by the service guy after an antenna change.  So I went up on the
> roof
> (it was 106 deg) with the receiver to sniff around.  Of course the noise was
>
> gone by then.
>
> I have a 13-year old, rooftop packaged Trane heat pump model WCZ060F100BD
> near
> the Wi-Max system and while I was on the roof, it turned off and the noise
> erupted.  The heat pump was the source, but not while running.  I could hear
> an
> audible buzzing sound inside the box.  I pulled the fuses and all was
> quiet.
> Plug them back in, noise, both audible and RF resumes.  Heat pump turns on
> to
> cool and noise is gone.
>
> Investigating inside I determined that the potential relay was chattering
> when
> in standby.  When cooling it pulls in, disconnects the starting capacitor
> and
> the unit runs normally.  No one but a ham would ever know there was a
> problem.
> Looking at a generic schematic
> (https://www.achrnews.com/articles/93735-potential-starting-relays) I don't
> see
> how this can happen.  Clearly, there is more to this.
>
> Unfortunately, Trane (American Standard) guards their schematics like gold
> in
> Ft. Knox and I've been unable to find one for further troubleshooting.  I'm
> open
> to any and all ideas.  Links to a complete schematic would really be
> appreciated.
>
> Wes  N7WS
>
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