Hi again Stephen,

Here's another long one to read in your spare time. You can publish my works not copyrighted, make some money to finance your boat anchor restorations. Those big vacuum caps command big bucks proving once again Amateur Radio is a rich man's hobby except for us, champions at the sport of Dumpster Diving. Phil K2PG, Tubewormius Splatasaurus, invented New Jersey Mud Diving... a long story in itself.

I thought the project was finished, I now see not. Thinking back to my daze hanging around WERA and observing how the RCA BTA1R 1KW operated at 1/2 power behaved here's the scoop on the 4-400As. There were 2 in parallel RF FPA modulated by 2 P-P, the modulators glowed because the DC voltages were in normal operation while the audio voltage was half. The finals operated at the 500W output level (BC transmitters are rated and operated at specified RF output) didn't glow which prompted me to tell Bob the CE to swap them when the BTA500R was operating every other month. It BTW used 4 4-250s and all glowed. So the bottom line is such tubes should show color when operated at their normal operating voltages. Since I only saw them in CCS plate modulated Class C service at WERA (also ICAS in a Collins 20V as the K2PG 160M transmitter) I can't say anything about Class AB2 SSB/CW service with only a 20% duty cycle, but likely with a couple of WA1HLR atomic YYYAAAYYYLOOOs they'd glow momentarily. (;->) Timtron is living proof that genius and insanity go hand in hand.

Yep, that white film is barium oxide, it used to be silver barium metal flashed on as the getter. You're right, the seals are broken and air entered the rarefied neon or argon atmosphere. Since there's no way to test them I know of my test was if they light up inside the cathode cylinder they're good. Ah yes the 5U4 full wave vacuum rectifier the previous owner used in place of the stock 5R4. My best guess why they were in so much Amateur gear is they were dirt cheap JAN (Joint Army Navy) surplus, but the 5U4 common in TV sets is actually rated higher than the 5R4. I was awash in tubes I scrounged, tested, and sorted, I could afford destroying them in my power supply with the output shorted. ('->) It doesn't matter when a tube was made, unlike electrolytic caps and carbon composition resistors they don't go bad in storage. Old Timers will tell you that 1957-1959 was the highest sunspot peak and the best DX in radio history. FYI 1957 was IGY, International Geophysical Year that saw a massive spike in what today is known as Earth Science, good reading if you can find what's left of scientific papers from the studies.

"Also pondering the 160m mod in the back of my mind."
Are you pondering what I'm pondering Pinky?
Uh, I think so, Brain, but we'll never get a monkey to use dental floss.

Electric Radio, in the Victorian age it was the age of coal and steam. Naturally G1AVQ like all other radio hams built stations along the Radio Steampunk design, and this one is fully operational. Here's where things get sticky, I don't know if you're building in another Frankenstein Laboratories where I built an ATU for a friend out of parts from a 10KW AM transmitter, or if your grandfather was Sweeney Todd The Demon Barber of Fleet Street. (;->)
"I am thinking that my plate choke L7 needs another 25-50 uh or so."
Why?
"Its a National R-175A I am told"
If it looks like the picture you were told right.
"and apparently if I can find a way to add some more turns in line with it"
Not on that form, there is no room, and the tab on the mounting bracket is where the plate bypass cap goes. That's where Johnson effed up again with a single 500mickymike (that's what we called them before puffscofarads came along) TV doorknob, it should be .001uF at LEAST.
"enough to cover the extra L"
If you think it's necessary you can sky wire (remember there's high voltage here, hi) a 50uH single layer solenoid wound choke in series. In a way I miss the old days when I had scads of them and other salvageable parts clipped from discarded TV chassis.
"keep it shorted with a relay until needed, would be the goal."
Relay not needed, shorted not needed, this is not a resonant circuit, just 2 chokes in series. (145uH + 50uH = 195uH) I lost count of the finals I built up to 100W using 1mH 3 pie & 2.5mH 4 pie RF chokes, they're good up to about 900V or so and wasn't concerned about distributed C in low power low frequency circuits. The R-175A choke is a revised version of the R-175 choke. The revision has made the reactance of the choke high throughout the 6 meter band as well as the 10, 15, 20, 40 and 80 meter bands. The R-175A choke is suitable for parallel-feed as well as series-feed in transmitters with plate supply up to 3000 volts modulated or 4000 volts unmodulated. Inductance 145uH, distributed capacitance 0.6 pf, dc resistance 5 ohms, dc current 800ma, voltage breakdown to base 12,500 volts.

You're right, you will need more coupling capacitance, perhaps another 500 puff TV doorknob. (;->) Here voltage is less of a consideration because the circuit is designed to match to a 30-600 ohm load, 50 ohms if you have a 1:1.5 or less SWR at the output terminal. Here is where RF current rises sharply, not having a BSEE I can only guess somewhere between 5 and 10A. This is why there are several small values in parallel to distribute current between them like I used to replace the exploded cap in an ATU. Right again, at SW2 to keep them all together. I absolutely ABHOR butchery, adding another switch on the front panel is butchery, changing SW2 to a 6 position shorting type ceramic rotary switch is a neat and clean job, but a bit more difficult than at first glance. Another of Johnson's bad habits was double front panels with everything mounted both on the front and on the sub panel behind it. Yeah, either way you'll have to disconnect everything from the front panel and remove it to get at the sub panel behind it. (:-<) <groan> Another idea is your relay (preferably ceramic insulated for low loss if you can find one today) operated by a switch on the rear chassis skirt, far less obtrusive than cutting a hole in the front panel. Mounting the switch on the front introduces problems of its own like a bowed in panel unless you mount it the same way as everything else and it still requires removing the outer panel. Bearing in mind we're dealing with fairly large circulating current here I'd use a DPST NO relay with contacts rated at 10A and wire the 2 sides in parallel, that should do it. With the rotary switch set with all of the caps in circuit you'll have to experiment with the value of the extra loading cap so the variable tunes up at or close to center rotation, it's good to have a little wiggle room on each side. From Warren's Hints & Kinks, an air variable of known maximum capacitance connected temporarily makes taking a good guess at the final fixed value easy. A lyric from KC & The Sunshine band says it all, "That's the way (uh huh uh huh) I like it.". Irony has it that when that amp was made before KHz it was KC, so let the sunshine in. (Another stolen lyric from The 5th Dimension.)

"The relay connection may be a little tricky"
Not at all, it's eminently practical, it only takes a small hole drilled in the chassis to mount a 115VAC relay and some 14ga bus wire to connect the contacts, then wire the coil and switch to the mains hot and other side of the coil to the chassis. If the mains input is wired correctly with neutral to chassis you'll get 115V from hot to chassis regardless if the transformers are wired for 115V or 230V primaries. Unfortunately there is no DC of the correct voltage or low voltage AC available, so if the relay buzzes flip the switch and it should quiet. AC relay coils are shaded pole like small motors, but the armature doesn't always land solid.

"but as long as I remember to engage it first BEFORE keying up, that ought to greatly diminish the potential for sparks, flames and or smoke...."
The rationale of a killjoy. (;->) That would not allow for an interesting sign on, "With a flash of flame, a shower of sparks, and a puff of smoke KA2PTE is ON THE AIR! Hello CQ CQ CQ, hello CQ, how are you today? CQ CQ CQ...". The only thing missing is The William Tell Overture, you may recognize that as the intro to The Lone Ranger radio play and later TV series. QSL Kimosabe?

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