From: "stephane.mazzoni" 
Subject: [drakelist] DRAKE R-4C restoration - S-meter may be not deflecting
sufficiently

-100V (?!)
Practically, I observe -69V supplied to this circuit. All 1N4148 diodes =
(CR1, CR12 and CR13) of this circuit have been checked and found OK.

According to Instruction Manual, page 5-9, figure 5-3, schematic =
diagram, the power supply should generate +150V for the plates.
The plate voltages should be according to Instruction Manual, page 5-4, =
column 5.
Practically, I observe that the voltages checked are OK.


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Subject : DRAKE R-4C restoration - S-meter may be not deflecting=20
sufficientlyReference : S/N 18518 DRAKE R-4C "4-position mode=20
switch"Dear friends,I've corrected the
dial gear problem. =
here comes=20
another one :I've investigated a lot on this receiver during this =
week-end=20
and would like an advise for diagnosing and correcting the S-meter =
sensitivity=20
which I found insufficient.Best 73s and thanks for your=20
suggestions,Steve.___________________________________________=
_____1.=20
ContextThis R-4C (4-position) is equipped with the AM filter, the =
two 250=20
and 500 Hz CW filters and the 4-NB noise blanker. It is combined with a =
T-4XC=20
S/N =3D28513 and an MN-2000 matching network.The antenna is a =
FRIETZEL=20
Conrad-Windom wire antenna type FD-4.All wafer tracks and sockets as =
well as=20
all pins have been fully cleaned.I do not have the chance to get =
access to=20
any RF generator or lampmeter, =3Dhowever I can make comparisons =
with a=20
KENWOOD TS-930S.2. What is observed :Even
with the strongest =
signals=20
heard on 3,5 and 7 MHz bands, the S-meter would not go higher than S9 + =
10 dBs=20
on the strongest signals (i.e. broadcasting stations on 40m).On the =
other=20
hand, the actual sensitivity seems to be good on all bands with respect =
to the=20
TS-930S rx : i.e. the smallest signals that can be heard on the TS-930S =
seems to=20
be also audible on the R-4C.A difference of more than  20 dB on =
S-meter=20
readings is experienced =3Dbetween the two receivers.The AGC =
time constant=20
selection switch on front panel of the R-4C =3Doperates =
normally.For=20
reference, the Xtal calibrator signal is :S9 on 7000 kHz,S9+10 =
on 7025=20
kHz,S9+5 on 7050 kHz,S9+10 on 7075 kHz,S9+5 on 7100 =
kHz.The=20
80m noise level at night is around S6/S7 and the strongest stations =
would not=20
deviate more than S9+5.On the STBY position of the Function switch, =
the=20
S-meter deviates to S9+35dB.3. What has been learnt from the=20
documentation about the AGC and S-meter settings :There are three =
possible=20
adjustments :a) The "zero setting" of the S-meter,
R-32, on the rear =
panel,=20
which should be adjusted for S-3 with a 1 microVolt RF generator =
input.b)=20
The "bias setting" of the AGC, R-55, which should be adjusted for =
=3DS-1 with=20
no signal at the input.c) the "sensitivity"
adjustment of the =
S-meter,=20
R-36, which should be adjusted for S-9+60dBs with a 30 milliVolt RF =
generator=20
input.
The original settings have not been modified. Except R-36 for =
test : at=20
full range of the adjustable, the maximum possible S-meter deviation =
obtainable=20
will not exceed S9+30 on the strongest stations (i.e. broadcasting =
stations on=20
40m). NB : after this test, the setting has been put back to its =

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