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I apologize for making 2 threads about the same issue. This is the same 2x 4cx300a amp w/ Tetrode boards I been tooling around with for awhile. Brondon 7861 suggested decreasing the Termination resistance and I'll try that next if the 6A10 diode doesn't survive. Nomad HVPS board surviving the...

A while ago, I lost plate current and found it was the single 5408 diode from B- to ground ("D-2", bypassed w/ low voltage .01 ceramic). The diode went open/No Connection. I replaced the single 5408 with two in series (same batch) bypassed w/ 2x .005 Z5U ceramics). I got zsac back but...

Heatsink isolated from coil and RF Termination Res. The 1st RF Term Res used the flange as R terminal. The R's in pic have separate leads each side of R.

50 was working rather well so I'll play with that for awhile. Waiting on two 100ohm I'll put in para for 50 at 500w also got a small heatsink w/fan. I want the roller to work it's my last-ditch effort before I replace it with something else. BTW anyone have a suggestion on how to mount these...

The 50R 250w RF resistor shorting the unused turns of roller gets very hot on 40 but much not so on 10-20. So far amp working fine roller stopped arcing. A long key-down on 40 would be too much for the heat. Larger resistor? Resister on a heat sink that is 1 x 1.25" (no fan) mounted high on...

Experimenting w/ shorting unused section of roller inductor before I replace it with some other device. 1st try yesterday: 5.6uH molded choke (1w sized-body) series connected to a 250w 50 ohm RF termination resistor w/ heatsink (TO-220 size). Seemed ok on 10 & 11 and 20 into DL with 5w AM...

This thread was a good read that brought back memories of my Golden Eagle 750. Still using 1/2 the plate transformer on an audio amp.

I was looking up Yaesu’s FT-767GX (MRF422 finals) and CoPilot’s Answer/Reply credits WorldwideDX. Nice work gents!

Thank you for your analysis. Happy day though because I have 200mA zsac again! Made lots of improvements since last tubes ran & I'm eager to setup again w/ radio & DL again. Have entirely new input section and coil arrangement to test. Cycle never ends but I'm getting better at it. I...

B-minus 5408 went short. I believe this is from the 'bang event' I described a few months ago. Wish I had found it earlier but the bright side is that it prompted me to re-do the RF Input. Hoping it's an easy fix. I thought it was supposed to go open like a fuse though. Is there a better diode...

I have lots of length and height but only a bit over 3-1/2" of width available. This is going to take some time to find a larger unit that fits, width-wise. Meanwhile, I will try shorting the unused turns of the roller with RF termination resistors. Waiting on 50R/250w part now. Perhaps a...

Sooner or later the roller inductor must go. One problem w/ roller I suspect is that it’s too small for two 4cx300’s. Before it gets replaced (looking at Variometers,UR4LL’s website has a few Russian pieces that may work HF 10-40), I want to experiment with connecting the unused ends of the...

OK, I think I get your meaning. IOW, a standard 10w 25R ww part is fine for my purpose.

I’m nearing the end of my 4cx rebuild -for this year anyway- and the resistor I’ve had between HVPS and plate choke has seen better days. It’s a single long body ww from almost 2 decades ago. After checking the W8JI website I see there is a better part for this function: RCD Part Number...

Had the Radio Shack 100mW collection as a child but it was 1973-74 that my friends & I all got base stations and by age 16, radios in our first vehicles. Suburban life was RF paradise. CB license KES4175, it cost $5 I think.

Used 2x 6 pin sockets glued together Worked thanks for suggestion.

8-Pin DIP Wire Wrap Sockets Texas Instruments found these on ebay. May not need anything though as the Can type 748 delivered today. The leads are long enough to use existing socket......I think. I'm working through the pinout conversion now. Going from AM748 with TO5-8 round can and a...

I ordered the Fairchild can. Waiting for it now. Removed tetrode boards found a cracked trace under a 220 style, 3- terminal regulator. I had tried sockets long time ago but they did not work out, kept coming loose. In a perfect world the parts are soldered in place amp sealed up and never...

Yeah, I get it now. Good idea, Fairchild can-type 748 soon.

OK, trying to avoid removing the boards and sockets. I'm at the ordering stage Think I'm going to try it. Leads look long enough. There are metal can-type Fairchild 748's on eBay for approx $10. Wait a minute, that's a double-sided male pin adapter in the pic? I never saw one before. Yeah...