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Correction to V2 analysis: Pin 5 is the AM detector. In AM, the radio uses V2 as the AM detector and as the first audio amplifier, but only in AM. I also added some more paths for the sidetone path.

Analysis of V2: Pin 1 should be 0 if there is no key plugged in or a key is plugged in and the key is keyed. In key up position, this pin should be negative SOMETHING (in RX) because this is the grid

Claudio, I have a box of vintage semiconductors that I've recently inventoried, and in it are several 2N5109 transistors. I've had these parts on a shelf for 20+ years, so I'm confident they're not

I got back to the TR4C today. I disassembled, completely cleaned and inspected the mode switch, found a couple of bent fingers and straightened them and cleaned the switch fully. I did get the AM Mode

I’m at a place called CPC in HAUPPAUGE, NY. Been here for close to 3 years working from the 3T’s to the 9T’s. T stands for Tesla. I’ve been doing RF for over 34 years at different companies

I see you know your way around! I worked on NMR instruments, specifically the Varian XL-100, back in grad school, early 1970’s. This was the first 100 MHz instrument! Of course it did not image

I can probably try those experiments that you just mentioned possibly tonight when I come home from work. I work on drivers and power amps all day long that go into MRI UNITS. Mark

There’s always a first! BTW I just bought another TR-4CW but it has the RIT. It should be arriving soon. So when I get it I will definitely see if that one does it too! Mark

I would not suggest live-pulling of the Jones plug! That could be a significant safety risk. I meant that you should, with a clip lead or similar, short the wiper to grind before you pull the AC mains

Also to pull the jones plug off of the back of the rig to turn off the rig I feel is not a good idea. Mark

Also to short out the wiper to ground as I am pulling out (whichever plug) you would not hear anything the reason being is that the little mouse sound, squeal sound or whatever only last for a

So unplug the jones connector and not the AC cord. if I would to remove the Jones connector on the back of the unit I believe you completely shut off all voltages going to the rig. If I just

OK, two more things: DO the same test but, as you unplug the power supply, short the wiper of the AF gain pot to ground. Also, try normally shutting the radio off with the switch but in the AM mode

OK Gary I turned both gain and volume up to full blast and unplugged the rig and it does not make that noise. Mark

I forgot, the AF Gain pot is also the power switch. It’s been around 15 years since I last saw a TR-4, 4, 4C etc. So obviously the issue lies in the AF stage. It would be an interesting diagnostic

Thanks for those kind words John. Initially when the rig was acting up I was so so close to just tossing it! But the more I started troubleshooting the more I started learning about this rig,

You don't turn your radios off from a power strip? "Mark N2DMI via groups.io" <markkiziuk1@...> wrote: -- 73 -Jim NU0C

You only hear the sound when you turn the rig OFF! Varying the AF gain doesn't make sense.

And that's how I sound after you get a couple of beeahs into me... Steve Wedge, W1ES Time flies like an arrow.? Fruit flies like a banana. Sent with Proton Mail secure email.

... "and don't drive like my brother!" Barry - N4BUQ