I am using my brain again and it might get me into trouble. Thought I would check with you guys before I burn up a tuning eye. I have a Zenith 11S that I have completely recapped and then some. It works great except for the new tuning eye. I subbed in a newer 6E5-tuning eye I found on Ebay for the missing socket and 6U5 eye tube. It came with a schematic on how to correctly wire in and it does glow a bright green as expected but…… it does not close when on a station. It barely moves when I go off and on a station. I have a 1Mega ohm resistor in place just like the radio eye called for originally but wonder if I should go to a lower resistance to make this particular tube react better to on off channels. I know the eye tube can close because I shorted across the resistor briefly and it closed nicely. I also have been through the chassis setup many times with no issues found. I even removed the can to check out the IF can wires to make sure all was well. I receive many stations and don’t see an issue with the tuning. Wonder if anyone else has had this problem. I also noticed Zenith liked to write M for resistance on all there schematics for Kilo ohms. Is this the case with this jumper resistor? Thoughts? Thank you for any help. Joe

What do we think about using a 1/4 watt resistor instead of a 1/2 watt? Just read a past post and thought maybe this would make the eye work. The resistor is no longer internal. I used a regular tube socket to connect the new version eye tube. It works great, as long as everyone keeps there hands off of the pin tabs. Haven't done it yet but bet it will scare you at least.

Changing the resistor wattage won't change anything.

The eye tube closes based on the automatic gain control voltage. Check that - if the AGC isn't working, then neither will the eye tube.

Do you notice that for very strong stations, it's difficult to turn the volume down all the way?

:What do we think about using a 1/4 watt resistor instead of a 1/2 watt?

I am learning more about AGC. With tracing lines off of the schematic I am guessing the problem could be associated with a bad 1232 RF tube or the 6A8G tube. Here are some more clues to the puzzle. The local and distant switch hasn’t been tried yet. It that works I can assume that the 1232 tube is good? The 6K7G is recently store bought and I have swapped it out with no difference in eye tube feedback. SO that leaves me with the 6A8G tube along with the dual 6V6 tubes. I have been through that power amp section thoroughly. All caps and resistors are new. Even the bar ohm resistors have been replaced with exact resistance 5W resistors. Not much left so that is why I am leaning towards a bad tube. Don’t see the 6Q7 det amp or the 6J5 inverter having feedback to the first two tubes or back to the 6U5. Aim I correct in assuming that these are out of the AGC loop? Again, it is a Zenith 11S-474 that has been recapped w/ most all resistors swapped. Works great but tuning eye won’t close, just glows. Thank you for any help. Joe

I think you'll need to troubleshoot this in a systematic manner. Best not fall in a spiral of replacing parts.

With a voltmeter, you need to find out why the negative AGC voltage isn't getting to the eye tube on stronger signals. The AGC bus connects to the 6U5 grid. It originates from the 6Q7 detector diode. The AGC voltage also goes to the grid of the 1232 (via the local distance switch) and the grid of the 6K7 (via R8). Trace out the AGC circuit to see how it works - and where the AGC voltage is being lost.

Also, the 1-meg resistor should be inside the 6U5's tube socket. Mounting it remotely might cause funny behavior due to the capacitance in the connecting cable.

:Also, the 1-meg resistor should be inside the 6U5's tube socket. Mounting it remotely might cause funny behavior due to the capacitance in the connecting cable.
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Lewis