Eddy,
The first thing I would try is substituting another tube. Some tubes seem to be more sensitive to changes in voltage than others. I was able to cure a drift problem in a Collins 310B transmitter by changing the master oscillator tube. Barring that, you could try regulating the filament voltage, but check the DC voltages as well to see if they change with your line voltage. There is more than one possible source of drift. A somewhat noisy and expensive solution is to run the receiver from a ferroresonant transformer that will give you a more constant AC voltage in spite of line variation. There are usually a number of them for sale on places like eBay. 73, Bob AD3K From: drakelist-boun...@zerobeat.net [mailto:drakelist-boun...@zerobeat.net] On Behalf Of Diane and Edward Swynar Sent: Thursday, December 30, 2010 1:11 PM To: drakelist@zerobeat.net Subject: [Drakelist] Drake R-4 PTO Heater Regulation Hi Guys, Per chance, does anyone reading this have any recollection as to the QST / "Hints & Kinks" edition which made reference to regulating the 6.3 heater volts of the 6AU6 VFO tube in the Heathkit SB-300/301 receiver...? I have the very same malady, I'm sure, plaguing my R-4 receiver. The station with the Drake Twins is located right between the sump room & the forced air electric furnace of the basement: whenever either (A) the furnace, or (B) the sump pump, or (C) the well water pump kicks in, the CW station I'm listening to will slowly start to drift a second, or two, after said device starts. Once the unit kicks off, the CW signal will return to "normal", again, after the prescribed second, or two. I suspect that unregulated heater voltage is affecting the PTO frequency, just as it did in the referenced Heath receivers... The "cure" in that instance (per that now-forgotten "Hints & Kinks" piece) was the incorporation of rectifier, small electrolytic capacitor, & a zener diode at the filament supply of the VFO tube... Ring any bells with anybody...? ~73~ de Eddy VE3CUI - VE3XZ
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