[Boatanchors] DX-35 help needed

[Peter A Markavage]

You need to read the circuit description. Paragraph 3: Plate and screen
voltage for the oscillator stage are derived from the buffer stage
cathode. The two 12BY7 tubes are operated in series across the 600 volt
supply and receive approximately 300 volts apiece.

Further:
Paragraph 4 Buffer: The 12BY7 buffer stage has an independent filament
supply to prevent heater to cathode breakdown as this cathode is 300
volts above the other tubes.


Pete, wa2cwa
http://www.manualman.com


On Sun, 8 Mar 2009 14:50:40 -0400 =?iso-8859-1?B?V9hRRkM=?=
<erastber at tampabay.rr.com> writes:
> 
> 
> 
> Looking at the schematic, the filament wiring for the 12BY7(buffer) 
> shows
> that pins 1, 3, 4 & 5 are tied together and go to "X" on the power 
> tranny;
> also goes thru a 47K to pin 2, thru a 470 to the switch & 40M coil, 
> thru a
> 27K to pin 8 of the 12BY7 oscillator and thru a 47K to pin 7 of the
> oscillator.
> 
> Questions:
> 
>  Why would the filament be tied to the cathode and grid of the 
> buffer?
>  Why would the filament be tied to the grid and plate of the 
> oscillator?
>  How would the oscillator get it's plate and screen voltages?
> 
> I am unable to dip the final and I believe it is because there is no 
> drive
> to the final grid because there is no plate and screen voltage on 
> the
> oscillator..
> 
> Your help and thoughts will be appreciated!
> 
> TIA
> Gene, WØQFC
> 
> Stuff for sale: www.w0qfc.shutterfly.com
> Web site: www.w0qfc.com
> 
> AF&AM #91 Lafayette CO
> 
> 
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