Jerry -
There are four schematics for the TR-4C. What is the s/n of your unit?
Actually Pin 6 actually goes through four resistors to get to the 60V
bus, R61, 62, 63 and 64. The RF GAIN control, R113, goes to ground from
the junction of R62 and R63.
R61 is on Board 10, which is the board with the component side up
against the front shield of the Carrier Oscillator section. The rest
are on Board 6, which is just behind the ZERO and ANTI-VOX pots. You
'really' need my CD! :-)
Give me your s/n and I can at least get you the correct schematic.
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
<www.k4oah.com>
Jerry Semones wrote:
I am restoring a TR4CW and have it working except for the AGC. I have
swapped out all of the tubes but I still don't have any AGC action.
While the S-meter does indicate signal strength there is no delay in
the movement. I have measured the voltage and resistance on the 12AX7
AGC tube with the following results:
PIN VDC
1 -.1
2 -51
3 -49
4 0
5 0
6 +1.17 (should be -0.16)
7 -51
8 -49
9 6.3 (fil)
Pin 6 which is the plate of the 12AX7 measured 1.2M to ground but
should be 2.2M according to the manual that I downloaded from the
internet. My schematic copy is not too clear given it's all on one
page in the download. It appears that pin 6 goes through 3 resistors
in route to a -60V source but I can't find that source on my
schematic. Can someone telll me where to find the source of the -60V
feeding pin 6 of the 12AX7?
Thanks & 73' to the group
Jerry K4FJK
2
3
4
5
6
7
8
9
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