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

10ms and=20
the delay time constant was very long. Only leakage currents and the =
bias=20
current of the op amp U1601 would discharge the ALC capacitor C1611. =
This not=20
only makes the delay time constants long, but also quite unstable with=20
temperature and life and variable from unit to unit/ 
     An=20
82k ohm resistor was added from the cathode of CR1603 to ground. This =
resistor=20
may be added by removing the bottom cover of the TR7 and soldering it =
between=20
the CR1603 end of R1617 and the ground end of R1615 on the top of the =
ALC board.=20
It is not necessary to remove the board to make this addition which =
leaves the=20
attack time at 10ms but gives a delay time constant of 92ms. =

     On the air
tests now show =
approximately=20
equal average power outputs from the TR7 and the 32S-3. DX stations now =
report=20
that there is little or no difference between the two units. Some small=20
additional improvements may be obtained by utilizing a dual time =
constant=20
similar to the 32S-3. "
It improved the audio on my TR7 drastically, =
so its=20
well recommended. It only requires a 82 K =
resistor!
 
Best 73 es
HNY!
Dick/PA2DW

  -----Oorspronkelijk bericht-----Van:=20
  owner-drakelist{at}www.zerobeat.net=20
  [mailto:owner-drakelist{at}www.zerobeat.net]Namens Bill=20
  CarpenterVerzonden: maandag 3 januari 2005 =
12:40Aan:=20
  drakelist{at}www.zerobeat.netOnderwerp:
[drakelist] Fw: TR7 =
Mike=20
  Gain
   
  ----- Original Message -----=20
  
From: =
Bill=20
  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=20
  quite a bit.  I replaced the muddy sounding cartridge in the 7077 =
mike=20
  with a Heil HC-5 element and reports on audio quality are much better =
now.=20
   I was surprised that the output of the mike did not improve. =
 I=20
  still need to run the mike gain at about 3 o=92clock to light the ALC =
led and=20
  get full output on SSB.  Since the HC-5 is low impedance I wired =
it=20
  through the transformer in the 7077 so it would match the stock high =
impedance=20
  input of the TR7.  Is it possible to wire the mike a different =
way to=20
  increase output?  I have heard that later TR7 models have a =
second low=20
  impendence mike input and maybe that would solve my mike gain=20
  problem?
   
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