From: "Dick Harms PA2DW" 
Subject: RE: [drakelist] Fw: TR7 Mike Gain


"Dick Harms PA2DW"  made an utterence to
the drakelist gang
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Hi Bill,

I had eactly the same problem with my TR7, but I also noticed that the ALC
was rather slow in action. I found this on the internet, written by G4ALG:

"Examination of the TR7 ALC indicated an attack time of 10ms and the delay
time constant was very long. Only leakage currents and the bias current of
the op amp U1601 would discharge the ALC capacitor C1611. This not only
makes the delay time constants long, but also quite unstable with
temperature and life and variable from unit to unit/
     An 82k ohm resistor was added from the cathode of CR1603 to ground.
This resistor may be added by removing the bottom cover of the TR7 and
soldering it between the CR1603 end of R1617 and the ground end of R1615 on
the top of the ALC board. It is not necessary to remove the board to make
this addition which leaves the attack time at 10ms but gives a delay time
constant of 92ms.

     On the air tests now show approximately equal average power outputs
from the TR7 and the 32S-3. DX stations now report that there is little or
no difference between the two units. Some small additional improvements may
be obtained by utilizing a dual time constant similar to the 32S-3. "

It improved the audio on my TR7 drastically, so its well recommended. It
only requires a 82 K resistor!



Best 73 es HNY!

Dick/PA2DW

  -----Oorspronkelijk bericht-----
  Van: owner-drakelist{at}www.zerobeat.net
[mailto:owner-drakelist{at}www.zerobeat.net]Namens Bill Carpenter
  Verzonden: maandag 3 januari 2005 12:40
  Aan: drakelist{at}www.zerobeat.net
  Onderwerp: [drakelist] Fw: TR7 Mike Gain



  ----- Original Message -----
  From: Bill Carpenter
  To: drakelist{at}www.zerobeat.com
  Sent: Sunday, January 02, 2005 8:52 PM
  Subject: TR7 Mike Gain


  I love my TR7 SN 7398 and use it quite a bit.  I replaced the muddy
sounding cartridge in the 7077 mike with a Heil HC-5 element and reports on
audio quality are much better now.  I was surprised that the output of the
mike did not improve.  I still need to run the mike gain at about 3 o’clock
to light the ALC led and get full output on SSB.  Since the HC-5 is low
impedance I wired it through the transformer in the 7077 so it would match
the stock high impedance input of the TR7.  Is it possible to wire the mike
a different way to increase output?  I have heard that later TR7 models have
a second low impendence mike input and maybe that would solve my mike gain
problem?



  Thanks and 73,



  Bill NZ0T

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Hi Bill,
 
I had eactly the same problem with my TR7, =
but I also=20
noticed that the ALC was rather slow in action. I found this on the =

internet, written by G4ALG:
 
"Examination of the TR7 ALC indicated an attack time of =

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