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Looks very much like lightning damage to me. That board would normally only have low levels of RF drive on it. However, in receive, a lightning strike works it way right back to that input connector with the fried choke. Looks like the keying board took most of the energy discharge first...

Cool. You'll probably notice the Maco tubes, look identical to the GE, because they were all made by GE. Someplace on each tube, you are likely to see the 188-5 code. That indicates manufacture at the GE, Owensboro Kentucky tube plant.

The red wires coming off of the relay are short enough to not make much difference at 27 MHz. I would leave them alone. However, that coax being unshielded is way too long and it passes right by a very critical area on the input tuning for that final stage. That needs grounding at both ends. I...

I've seen this problem before when I experimented with $1.27 TO-247 MOSFETS in a 170 volt line powered linear. The best thermal tracking could not respond fast enough to the temperature changes occurring inside the transistor die. If thermal tracking is intact on the RT-5 finals for the RCI 69...

The problem is the Ranger RT-5 finals. Biasing a switch mode MOSFET into the linear region for clean SSB use is somewhat tricky. They are instable enough to be very dependent on temperature compensation in the bias circuit. Sometimes the diode or thermistor used to sense the temperature, is not...

One other thing I noticed is the RG-8 coax left its shield completely ungrounded. This is bad because it will radiate output power, right back into the input circuit the coax passes by. Ground both ends. Also, do you know what happened to this amplifier? That keying board is so fried, I can't...

If the capacitor let the smoke out, there is a likelihood that the diode feeding it is also shorted. Check with your meter to make sure the diode only conducts in one direction before installing the new capacitor. The positive side of this capacitor is your DC output to run the relays.

If you can only find AC in this amplifier, you've found the problem with the original keying circuit. The amplifier must have DC to run its keying circuit. As I took a moment to look at your picture, I can confirm the reason why you have lost dc. Look at the small gray electrolytic capacitor...

Unless you had a situation of severe receiver overload, such as somebody parked in your driveway transmitting, these diodes would never have enough RF voltage across them to even begin to conduct or rectify in the recieve mode. They do have some internal capacitance so they are acting as nothing...

That's the first time I've seen an input attenuator labeled as a Clarity switch. Do some positions produce distortion?

Did anyone notice something is different about that one transistor driver stage? I only see one Broadband Transformer being used? I'm assuming that's on the collector of the driver transistor as the output matching device. What are they doing on the input? I really can't make it out well from...

1) Neutralization takes place through a separate circuit in the amplifier. It is not a function of the tube. In others words, there is no such thing as buying a neutralized tube. 2) This is entirely up to the operator. The tube can handle more abuse and drive. The amplifier cannot. If the tube...

There was a time when an 811A tube, could handle a little bit of cherry red on the plate. The problem is, they haven't made a real 811A in about 50 years. This new garbage that they make with the same part number, where they strip the six radiator fins off of the side of, causes a plate to grid...

I think you're confused between plate dissipation that I am referencing, and rated output power for a given class of operation. I will admit, I made a mistake on the 811A plate dissipation, it's only 45 Watts.

Only when they run out of spectrum to auction off to the highest bidder or, run out of existing services to abolish in order to make more money.

Yes. That will prevent overdrive.

If you don't overdrive it, it won't be a splatter box. However, you will need to use an antenna tuner with it in order to get that input SWR manageable. As long as the output Tunes properly without the load or tune control all the way to one side, it shouldn't be too bad.

Nomad, after reading your posts for many years it dawned on me that you are are entitled to a big "Thank You" from this forum. I've seen few people put as much effort in as yourself, to answer other people's questions. You do it consistently and provide the correct answers. I'm pretty sure we...

You're making progress however, don't stop here or the tube won't like it. The -35 volts is where you want the 8417 bias in transmit. The -24 in receive is actually biasing the tube harder in RX. Bypass the existing bias contacts on the relay and connect those wires so the tube always sees the...

If the original D&A tubes with the double strapped, black anode cap are still good, they are far superior to anything you are likely to find in the Varmint. About the only exception would be if the Varmint had Amprex 6LF6 tubes made in Holland. That particular plant made the most reliable 12...