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The thing to look for is the plates on the Plate Tune control. The "twin peaks" rule is that in one 360-degree rotation of the knob you should see TWO positions with a peak on the meter. They might be close together, or 180 degrees apart. What counts is seeing two distinct peak positions of the...

And they couldn't protect airbases in Florida from hurricane season? What's wrong with this picture? 73

I would check for a resistance reading from each pin of the tube socket going to the chassis. Just sounds like a fault in that department. Maybe. Should be no DC continuity from any of the five mike-socket pins and the chassis. An analog meter may show a brief "kick" of the needle but no...

The underlying intent of a "Jewel Box" amplifier is to bias the tube beyond cutoff. Serves to attenuate the carrier and exaggerate the modulation envelope. So long as the tube is biased to cutoff, theory says you shouldn't need to shut down the screen. We do it anyway. Get a tube hot enough and...

I must be getting old. That thing gets heavier every time I hoist it off the shelf. My relay has two black wires. One goes to the upper fuseholder, or in my case circuit breaker. The other one goes to the lower-most screw on the barrier strip. The back corner of the cabinet is just too crowded...

Does this amplifier have a name on it? Might be worth knowing who to stay away from. 73

Who says? 73

Not so different from seeking a new door handle for a 45 year-old car. It's a dealer part, but the dealer no longer stocks it. That selector was used in a half-dozen brands that hired Uniden to make their 1978 SSB CB radios. A used one is probably your only hope. Biggest aggravation with that...

A second source named Liteon makes, or made an equivalent. The red one is "LTD-482PC". Used to get them from Digi-Key decades ago, but it's no longer a stock item there. Specs are attached. 73

Yeah, me too. 73

Hey, that's what a warbly SSB radio needs. A DDS. I bought one of those or one like it and haven't tried it out yet. Want to try it with a tube radio. 73

If it's exactly the same, I'd have to guess the relay doesn't actuate when you key the mike. If you can see the relay armature click over when you key the mike, that means the transistors are getting the radio's drive power and putting out exactly the same power the radio feeds into them...

My experience points to excessive RF circulating currents. Maybe. Seems like that 'fuse' link should handle the tube's DC current. Running the amplifier peaked incorrectly is what I blamed it on most times we saw this. Big hazard there is with amplifiers that parallel four or six tubes. The...

Pretty sure that one uses RF transistors that mount by a threaded stud that pokes out the underside of the heat sink, each secured by a nut on the outside. That one is famously prone to fail from excess drive wattage, or high antenna SWR. Clobbers the two RF power transistors. Finding...

Rock on! Congratulations. Gotta love it when a plan comes together. 73

That is the oldest version, with three relays. This model puts the final tubes on standby in "Low" mode. Has a separate Tune and Load for Low side. The third relay, seen between the two sets of tubes directs the output of the driver tubes directly to the antenna for Low side and directs it into...

More like disinfotainment. 73

We call this the "blown fuse" syndrome. The 8950 tube seems to be susceptible to this sort of failure. This one was. Learned to eyeball that thin link from pin 3 to the cathode at the center of the tube before even bothering to put it into the tube tester. 73

Adding a capacitor from the audio signal to ground will cut the highs. Might or might not help the "nasally" sound. Might try larger values than .01 for the series cap and see if the tone is better balanced. It's like pin-the-tail-on-the-donkey, but without the blindfold. 73

Well, there's a problem. A switch transistor will always require a finite period of time to make the transition from on to off, and vice versa. If this switching time is short enough, it can amplify RF. The shorter that time, the higher the frequency it can amplify. The higher the power...