You have to be careful here. there are many hidden things that may be going on here. Increasing the gain of the IF amplifier to max with the pot may induce the IF amplifier to oscillate. I would reduce the gain and increase the RF generator to +10 or +20 if necessary to force a signal through.

What you must confirm is that when you see a deflection on the meter, always confirm you cange vary the level properly eg a smal increase in input yields an increase in the output and vice versa. If you overload an amplifier, sometimes you will find the change of input yield no output change. Or increasing the input may reduce the output. Always make sure increasing the input will increase the output.

You have to understand and get a feel what the circuit is doing. Instead of the VTVM, you could use an oscilloscope on pin 1 of the 12AU7 to see the 1kHz sine wave amplitude. I sometimes like to check things visually to confirm there is actually a sine wave there and I am not just measuring noise. Additionally if the amplifier is overloading, you will see the sine wave clipped. And if the amplifier is oscillating, you will see that too.

I think you need to go to +10 on the HP 8601a.

+10dBm got it. I like the idea of using the scope as an addition to the analysis and I will attempt to employ your suggestions. I appreciate all of the time you have generously provided. I might end up not being able to get this working right but I’ve learned a lot about IF signals as well as design and what engineers in the late 1940s were thinking and trying to achieve.

We have gone so far. I would like to see you finish this and make it work! 😄

Me too:yes:

Considering the level of commitment, so far, along with your spare parts chassis, there's no reason to expect anything other than complete success. Slowly and methodically it will happen. :thmbsp:

Thanks Kevin...hangin' in with it.

I put the scope on pin 1 of the video amp and I’m not getting a signal through. I tried it at +10dBm. Something in the tv hardware may be amiss. Tube testing and socket check up next. Strange that when I inject an fr signal through the tuned I see a fairly decent quality image. Sound is way off…picture on channel 3 and audio on 4.

But it was working before? I would check the generator. Is that range switch still wonky?

Yeah but I checked the output on my scope and the frequency is spot on and varies with changes as does the amplitude. The 8600 has the frequency output as stable and correct. I’ll make sure the tubes are good and seated in their sockets. If I’m getting a signal through using my video generator through the antenna please, the signal should be at V106 right?

Is the 1kHz modulation selected? The VTVM on pinn 1 of the 12AU7? What is the bias pot set to? You and see the RF on the scope at +10?

Yes, yes, -4V DC and I see it coming out of the 8601...I just don't see anything at the 12AU7. Don't spend any mental sweat thinking about this right now until I get everything checked out and make certain I'm not doing something stupid. Can't get back on it tonight but maybe tomorrow or Friday. Stand by!

Hi folks. Just a brief update. Gonna need to take a break from this for a bit. Family stuff has come up and my time priorities have shifted for the time being. I'm not talking about months, just a few weeks until after the Thanksgiving holiday. As I've mentioned before, I have a 95 year old dad suffering from dementia. He's in a facility and has taken a recent turn for the worst so my wife and I need to reboot his situation and ours to deal with his needs. In some ways, this KCS28 has been a refuge from the storms so I hope to be back on it and reactivate it in a few weeks. Thanks everyone. Just didn't wanna leave y'all hangin'!

Thanks for letting us know.

No thank you for your help and sharing your experience and knowledge…and for your patience!