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I’m not sure if those small yellow and green things are. I have one here, but going to have to get a magnifying glass to read. Really fine print. The diodes are 1N5420. I have some here from Arlyn. Bypassing B+, yes. I try to use 2-3 per transistor. Feedback resistors- yes, parallel 100ohm...

Before going any further. The DEI that were in it, did all 4 blow? If not, was it a transistor on each 2 pill section or were both transistors bad on one side? Trying to understand if maybe there was a problem before you changed devices. Also, when you checked voltage, think you said it was...

By the way, the 6-8” long wire from brass cap to output is a bad idea. Lead should be much shorter.

On the diode for biasing. I think they used 1N5408. Try replacing with 1N5420. Will forward bias 0.475v roughly. Much better than the 0.65V roughly. They are turned on so hard, acting like a switch.

I believe the bias is switched on when keyed. Uses caps and chokes to block DC and AC. Depending where at in circuit when keyed. I don’t like that design. Rather use a 3rd pole on relay.

I can’t tell what cap you have across input transformers, but it should be 470pf or 500pf. Not 330pf. Not sure if those are 2879 or 2879C? Should take around 230-240pf to tune input once caps across input are changed. If 2879HG, then needs about 170pf to tune output. If HG2879C needs about...

I’m sure if you call up Chris, he will make it right.

On a lot of the tube amp stuff, I try to use a Hi Q input circuit. Something like a 5 and sometimes higher (11M) stuff. Won’t do anything for IMD, but it really helps on the harmonics.

Actually I just talked to Chris. Nope, he’s not making anymore of the BMT stuff. My bad

He’s also still making the BMT line.

Just a heads up, should be 500pf across the input transformers. If not, it will never Tune flat. Also, if you can tune flat with trimmer. I also try to overcouple by about 20pf. Seems to clean up signal some.

Might wanna double check bias voltage as well. Since that amp just uses resistor network, sometimes they fail. Think 1.8ohm or something similar. Also the HG are a little more finicky when biased. I did one where I used a smaller value like 1.2 or 1 ohm 2W if memory serves.

Yes the HG2879 is very fragile. Broken many of the tabs just lifting the legs to check device. Don’t forget when using HG devices they have to be matched or they will not play well. Overdrive and overvolting will kill them quickly. Once the device tests down to about 6 or below, they tend to...

I built a monobander using 2 of the rd100’s several years ago. Did well, a pair with 20w pep drive is pushing it. Saw just over 200w pep. Input was a little touchy, was only able to get down to 1.2vswr. Yes it has temperature controlled tracking. Did a little testing with. Worked well, but when...

Check bandswitch. Amazing how those cook when driven with a trashy radio. Could be bad cap, but with all of them reading high. I’m betting on harmonics arced bandswitch. Seen it many times

I had one recently I had to convert. It was beat up bad. Ended up mono banding it. I ran a high Q input in hopes of cutting down harmonics and hopefully prolonging the life of the parasitic chokes. Had about 660pf of total capacitance on input Pi. Lol. Bandswitch was smoked completely. Pulled...

The DEI and HG have to be matched. Not by batch number but by gain or hfe.

XForce is no longer. Not since late last year. Zapco/ Arlyn is out of the game.

Or remove transformer and install 3 switching supplies.

Since your using on sideband. Really the power supply needs to be regulated to keep signal linear. Same with bias. It should be regulated and include temperature tracking.