[ARC5] GRC-9 Update - II

[Robert Eleazer]

I found that the B+ power supply I built for my RT-70 over 30 years ago had inadequate power quality to run the new GRC-9 solid state LO and thus had to recap it.  This morning I found that with a B+ supply of 104VDC there is 8.5 VDC at pin 3 of the LO tube and that is adequate to run the LO.  Output at 2.41MHZ is about 40 MV.  So the original power supply for the GRC-9 receiver should do the job.

And as Mike Morrow suggested, there is not a 500 KHz frequency shift as a result of powering the LO with 13.5 VDC at the input rather than through the 33K resistor.  When I moved the wires around I must have been measuring at different spot, such as at the tuning cap.

By the way, the GRC-9 has a 270 ohm resistor (per schematic, 230 ohm by color code in the set) installed in the main B+ line.  I found this resistor measured at well over 500 Ohm.  I have seen older carbon resistors increase in value, although rarely by over 100%.  I paralled it with another new resistor to get it back to the correct value.  I'll be checking all the resistors in the set for such excursions.   

73's

Wayne
WB5WSV        

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