02-04-2022, 05:27 PM
Let me see if I can untangle your mystery.
The tube socket in the middle of the pic, the 7pin one is the 6A7 not the 78. The 78 uses a six pin socket. The 47,000 ohm is pretending to be #19 which is fine as long as it's with in spec. The loose end goes to chassis gnd.
You could have wired at pin 3 of the 6A7, #20A, ungrounded side of #19, and the left side of #22.
On the 78 (IF amp) the cathode and suppressor grid probably are connected together. If you measure the resistance from pin 5 the the chassis you should about 200 ohms. The later models have the suppressor grid grounded separate from the cathode. The 78 cathode is connected to the 6A7 cathode so they could use just one resistor vs two.
The tube socket in the middle of the pic, the 7pin one is the 6A7 not the 78. The 78 uses a six pin socket. The 47,000 ohm is pretending to be #19 which is fine as long as it's with in spec. The loose end goes to chassis gnd.
You could have wired at pin 3 of the 6A7, #20A, ungrounded side of #19, and the left side of #22.
On the 78 (IF amp) the cathode and suppressor grid probably are connected together. If you measure the resistance from pin 5 the the chassis you should about 200 ohms. The later models have the suppressor grid grounded separate from the cathode. The 78 cathode is connected to the 6A7 cathode so they could use just one resistor vs two.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got it!
Terry
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