[Drake] T-4XB Problem

[Garey Barrell]

Larry -

TUNE and CW generate power in two different ways.

TUNE is actually SSB, and is generated by converting the mic stage into an audio oscillator.  This tone is fed into the 
Balanced Modulator, similar to whistling into the microphone.

CW is generated by shifting the Carrier Oscillator UP about 800 Hz to place it within the LSB filter passband.  The 
Balanced Modulator is unbalanced by applying a DC current to the diodes in the BAL MOD, allowing the shifted CAR OSC to 
pass through.

It is NORMAL to have to increase the GAIN control considerably for CW.  Some transmitters almost full CW on higher bands.

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73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>

Larry Yates wrote:
> I am posting this for a friend of mine, Tom Webb, W4YOK.  If anyone has incurred this problem before and was able to solve it please let me know or you can email him at: sam9lives1 at verizon.net.  He has been struggling with this problem for a while now.
>
> Thanks,
> Larry Yates
> WA4PMA
>
>
>
>
> T-4XB PROBLEM
>
> Turn transmitter on.  Turn Function switch to "Tune" and tune up normally.
> Power output is 90 watts, normal.  Switch to X-CW and close the key.  Power
> output is 20 watts.  After 20 minutes, power output is normal 100 watts.
> Power comes up gradually, no matter whether key is open or closed during
> interim. Plate current starts out low, rises to normal.
>
> All tubes have been replaced with NOS tubes.  All tube voltages are correct
> both before and after warmup.  All resistors in the final circuit have been
> checked.  Problem occurs on all bands. Dummy load or outside antenna.
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