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#1
03-12-2015, 12:53 PM
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Resistor Puzzle
I am wondering if my schematic is wrong, I am working on a Sylvania chassis 336mu 1954. I am working on the audio section checking voltages. I am checking a 6W6GT tube. The sech, shows a value of 300v from transformer to pin 3 I have that voltage.Then it shows a 47ohm resistor from pin 3 to pin 6.At pin 6 I am supposed to have approx 140v, I have 300v same as pin 3. I tried another 47 ohm resistor still have 300v.the sech shows this is correct resistor.
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#2
03-12-2015, 01:25 PM
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Well, 160 volts drop across a 47 ohm resistor would imply 3.4 amps current which would be 545 WATTS! Can't be!
Check if the voltage specified has an asterisk or dot next to it.... many times the voltages shown are measured relative to a point other than ground. such as a 150 volt point, or something like that. Check for notes at the bottom of the page. Or it could be just a simple mistake.  jr
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#4
03-12-2015, 01:57 PM
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Pin 6 apparently is used as a tie point... there is no internal connection to the 6W6 from that pin.
I found a schematic for a (perhaps) similar 21" Sylvania set (ch 1-510-1) from 1953. It shows 240 volts connected to the output transformer and a 47 ohm resistor from the other end of its primary to the plate (pin 3) of a 6Y6 (same pin connections as a 6W6, 6L6, 6V6 etc.) output tube. The schematic indicates 120volts on the plate of the tube, with an asterisk/dot. A the bottom of the page it says " * Measured from the 120 Volt line". Perhaps they left out the note on your schematic... there simply cannot be a 150 volt drop across a 47 ohm resistor, unless it is glowing brighter than the sun! (and it won't do that for long)  Edit add: The resistor in the plate circuit of the 6W6 *might* be used as a fuse or to suppress parasitic oscillations. jr Last edited by jr_tech; 03-12-2015 at 02:08 PM. Reason: add note
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Linear Mode
