Carey,
I had the same issue with my T4X; it turned out to be the AC-4. As
Richard mentioned, use a scope or have a ham with a spectrum scope watch
your signal on key down. I installed the Heathkit shop PS kit since it
was long overdue anyway.
73, Mike W4DL
On 8/12/2012 12:00 PM, [email protected] wrote:
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Today's Topics:
1. hum in audio (Carey Lockhart, KC5GTT)
2. Re: hum in audio (Richard Knoppow)
3. TR4C Project unit for Sale (Pinholster Chris)
----------------------------------------------------------------------
Message: 1
Date: Sat, 11 Aug 2012 11:43:35 -0500
From: "Carey Lockhart, KC5GTT"<[email protected]>
To:<[email protected]>
Subject: [Drakelist] hum in audio
Message-ID:<6D2942AC77AE492DA2CE6D7BE329BAD5@careyflex>
Content-Type: text/plain; charset="iso-8859-1"
Hello All
I have developed a hum in the audio of my t4x. on am it completely wipes out
the audio and pushes the output up. on ssb it is there but not near as bad. you
can actully understand the audio. i have checked power supply voltages and all
is well. before i started poking and hacking i figured it was best to seek your
opinions.
Carey
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Message: 2
Date: Sat, 11 Aug 2012 10:00:27 -0700
From: "Richard Knoppow"<[email protected]>
To: "Carey Lockhart, KC5GTT"<[email protected]>,
<[email protected]>
Subject: Re: [Drakelist] hum in audio
Message-ID:<4962B628DC544DCC8F1AFF5FE836287D@VALUED20606295>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
----- Original Message -----
From: "Carey Lockhart, KC5GTT"<[email protected]>
To:<[email protected]>
Sent: Saturday, August 11, 2012 9:43 AM
Subject: [Drakelist] hum in audio
Hello All
I have developed a hum in the audio of my t4x. on am it
completely wipes out the audio and pushes the output up. on
ssb it is there but not near as bad. you can actully
understand the audio. i have checked power supply voltages
and all is well. before i started poking and hacking i
figured it was best to seek your opinions.
Carey
Make sure this is not power supply hum by checking the
supply with an AC meter or scope. There should be little
ripple. However, I suspect that you have an audio hum due to
a loose ground. The hum will be worse in AM because in AM
mode the side-band filters are bypassed. The audio goes to
the modulator which connects directly to the output tubes so
there is much more low end. If the hum is from the audio
stage there should be none in CW. Begin with the microphone
and its cable and connector and if not there with the
connector in the transmitter. One standard bit of voodoo in
much old equipment is to go through and work and tighten all
the screws. Very often ground connections are made through
them and they become slightly corroded in the same way as
the contacts on switches do. Working them will clean the
connection and often get rid of pernicious problems.
--
Richard Knoppow
Los Angeles
WB6KBL
[email protected]
------------------------------
Message: 3
Date: Sun, 12 Aug 2012 08:43:21 -0400
From: Pinholster Chris<[email protected]>
To: [email protected]
Subject: [Drakelist] TR4C Project unit for Sale
Message-ID:<[email protected]>
Content-Type: text/plain; CHARSET=US-ASCII
To those interested in a TR4C project.
I powered up this TR4C today using one of my AC4 power supplies. All the tubes including
the finals appeared to light up. I got sound but from the headphone jack. I wouldn't
attempt to try the transmitter except on a modified heathkit AC4., which I do not have. I
consider the unit as "lights up but non working".
The outside cabinet looks like it was repainted. There are decals on the
various jacks and side controls. The inside I would consider rough and dirty. I
think the unit could be refurbed. It might be a nice project.
I am attaching a website with some pictures I took with my iphone . The serial
number is visible in the rear photo.
I am pricing this at $150 as is, plus actual fedex shipping cost to your
location.
I am in Belleair Beach Fl 33786. If you have any questions you can call me at
727 409-9492
Chris Pinholster K4WIN
http://albums.phanfare.com/isolated/Lgk1ewt4/1/5706677
------------------------------
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