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  1. C

    GI46b linear, persistent AC hum on modulation.

    It’s not mine or it would have a grid and plate current meter. I had to temporarily install a plate current meter outside the deck so I could get an idea of what going on. I did install a fuse inline with bias circuit. It now has a glitch too on B+. The one thing I never see on Russian...
  2. C

    GI46b linear, persistent AC hum on modulation.

    Well new tubes arrived and installed. Amp sits at 2kv at idle. Drops about 300v when loaded. Took about 19V of bias. With a pair being driven, seeing about 1750pep into dummy load. Pulling 600mA at full output. ( I had to temporarily install a plate current meter to see what was going on)...
  3. C

    27 power wires on my amp, come on, really?

    The one aspect of using real copper 8awg, not copper clad wires. Also You can put 4-5 of the 1/2” x 1/2” 43 ferrites on each lead inside amp to help limit RF from exiting amp through power leads. Anything less and it’s not even worth doing since coupling is not the best.
  4. C

    27 power wires on my amp, come on, really?

    Curious as to what sized wire was used? Usually if 8AWG wire is used. Each wire is perfectly capable of carrying 50A. 12 x 8awg wire would be able to carry 600A.
  5. C

    ECA 1102 filament transformer

    I had to order proper resistors, using a pair of 10 ohm @50w in parallel on each leg. Will give me 5ohm at 100w. I measured current draw on each leg. 1.9A. So I rounded up to 2A. I figured my wattage dissipation to be about 20W. So with 100W rating I have lots of headroom. I’ll be using...
  6. C

    ECA 1102 filament transformer

    anyone ever use one of these. These were used in the Henry 8k amplifiers. I picked up a couple a few years ago and just got around to using one. The ones I have seem to run high on voltage. My line voltage is 249vac so I put on 250V tap. I was getting 8.5vac at tube. Each leg on contactor...
  7. C

    Strange

    Also worth mentioning, don’t use dielectric grease. Use Naolox or something similar. This is a conductive grease that prohibits corrosion.
  8. C

    schematic for fatboy 2 x 2879

    Also worth mentioning, sometimes you can find RMC / Mallory ceramic capacitors on eBay. I have bought several over the last few years. Usually N750 or N1500 @3kV rating. They work great in 4pill / transistor sections. Never had one fail yet. Tedss.com has some decent stuff if you spend the time...
  9. C

    schematic for fatboy 2 x 2879

    Which 2sc2879’s are you referring to? HG, RFP or Toshiba? Different values on the HG versus the Toshiba. Also what transformers are being used? Fat boy was using comp ( 5/8” x 1.25”) but lately they have been using the smaller 1/2” diameter 61 material. Usually 1.25” but I have seen some 1.5”...
  10. C

    So why do people in the "builder" world put down the MRF455 and 2SC2290

    I looked on RF Parts website a few days ago. Did not see any type of 2sc2879. Not the RFP brand, not HG or Toshiba. Not even listed as sold out.
  11. C

    4 pill hg 2879c output capacitor value

    Good luck trying to get a datasheet for the C version. I went to their website and couldn’t find one. As to the regular HG 2879, they basically copied the Toshiba specs. Yet it is a different animal.
  12. C

    4 pill hg 2879c output capacitor value

    4 HG 2879C, so many building with, using different turns on combiner or different sized ferrite and material. Different wraps on transformers or different size transformers. Multiple answers to that. What Shockwave suggests is easiest. Takes out the guessing. But I will say this. Using comp 61...
  13. C

    So why do people in the "builder" world put down the MRF455 and 2SC2290

    Guys spend too much time looking at wattmeter.
  14. C

    GI46b linear, persistent AC hum on modulation.

    Shockwave, it didn’t help that the shaft coupler for Tune/ plate cap spun without turning shaft on variable capacitor. Also the load cap was a air variable that only went up to 100pf with a 100pf doorknob in parallel with it. The Tune cap by the way only went up to 38pf. Granted you have some...
  15. C

    GI46b linear, persistent AC hum on modulation.

    Yes, they both are in scrap pile. I have ordered more. Neither one hi pot tested over 1kv.
  16. C

    GI46b linear, persistent AC hum on modulation.

    ChrisNomad, about how much bias did that 46B need. I’ll have to hook up a temporary plate current meter on this one so I can get 50-100mA of idle current per tube when amp is keyed, but no drive. The one I have here had about 15v of bias, but they used 1A diodes. I’m currently waiting on new...
  17. C

    Ameritron AL-1500 Upgrade

    Yeah, I understand the cost part. Only reason I ask, I have seen the AL-1500 transformer used for homebrew. Plate voltage was idling at 4,100+. Less than 50v headroom on each cap seems like it’s cutting it kinda close. That’s all.
  18. C

    Ameritron AL-1500 Upgrade

    Nice capacitor bank. Though I wonder why they didn’t use 500V caps for a little more headroom?
  19. C

    Toshiba 2SC2290B

    Does anyone remember what the date code was when they started making the 2290B? It’s been so many years ago that I do not remember.
  20. C

    Palomar Magnum TX2250HD - Help

    What radio are you using to drive this?
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