From: Garey Barrell 
Subject: Re: [drakelist] DRAKE R-4C restoration - S-meter may be not deflecting
 sufficiently

> between the two receivers.
> The AGC time constant selection switch on front panel of the R-4C =
> operates normally.
>
> For reference, the Xtal calibrator signal is :
> S9 on 7000 kHz,
> S9+10 on 7025 kHz,
> S9+5 on 7050 kHz,
> S9+10 on 7075 kHz,
> S9+5 on 7100 kHz.
>
> The 80m noise level at night is around S6/S7 and the strongest 
> stations would not deviate more than S9+5.
> On the STBY position of the Function switch, the S-meter deviates to 
> S9+35dB.
>
> 3. What has been learnt from the documentation about the AGC and 
> S-meter settings :
> There are three possible adjustments :
> a) The "zero setting" of the S-meter, R-32, on the rear panel, which 
> should be adjusted for S-3 with a 1 microVolt RF generator input.
> b) The "bias setting" of the AGC, R-55, which should be adjusted for =
> S-1 with no signal at the input.
> c) the "sensitivity" adjustment of the S-meter, R-36, which should be 
> adjusted for S-9+60dBs with a 30 milliVolt RF generator input.
>
> The original settings have not been modified. Except R-36 for test : 
> at full range of the adjustable, the maximum possible S-meter 
> deviation obtainable will not exceed S9+30 on the strongest stations 
> (i.e. broadcasting stations on 40m). NB : after this test, the setting 
> has been put back to its original position.
>
> 4. What has been measured :
> The plate voltages measured are all OK with respect to the Instruction 
> Manual, page 5-4, Voltage Chart.
> According to Instruction Manual, page 5-4, Table 5-2, voltage chart, 
> the AGC input on grid 1, should be within -1 to -1,5V.
> Practically, this is actually observed.
>
> According to Instruction Manual, page 4-2, section 4-8 S-meter, the 
> AGC line should swing to -40 V when the when the mute line is isolated 
> from the MUTE line.
> Practically, I observe that the grid 1 of V3 swings to -13 V and, the =
> grid 1 of V4 swings to -22 V.
> According to Instruction Manual, page 5-9, figure 5-3, schematic 
> diagram, the power supply should generate -70V for the operation of the =
> AGC circuit (Q7 2N3877) whereas this circuit is marked as supplied 
> with -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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On Behalf of Garey Barrell 
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