[Boatanchors] S38 pilot light
k4oah at mindspring.com
Wed May 29 09:47:49 EDT 2013
The tapped filament in the 35Z5 was _specifically_ for a pilot bulb, a #47, to be in parallel with one section, (PIn 2 & 3). IF this bulb
is missing, that section of the filament is overloaded and will open up, eventually. MANY 35Z5's met their death because the pilot bulb
burned out and theowner of the radio decided they could see the dial well enoughwithout a trip to the repair shop. Which came shortly
thereafter, to replace a 35Z5 with an openfilament section, surprisingly between 2 & 3. This is all explained, along with paralleling
additional resistors for increased current requirements, in any RCA tube manual.
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
Moulton, Robert M - (rmoulton) wrote:
> Thanks for the replies all
> The switch is now on the hot side as I believe it should be, plus I added a fuse for safety before the switch.
> I will need to check the voltages again, but I believe I measured 120V after the resistor for the pilot and at the pilot light socket w/o the bulb installed. I will measure across the resistor and from the #2 and #3 terminals on the 35Z5.
> Can anyone explain what is going on in this tapped filament circuit? At least a far as a properly operating one goes...:)
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