Drake L7 linear amplifier RF Deck #2 only, unpowered walkthru, this 1 is clean, I Likkie.
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- Опубліковано 18 лис 2024
- Drake L7 RF deck. This one looked great but had some internal issues. The band switch was bad and is a known problem with the L7's. The L4's used a much more robust band switch. Since I had deck number 1 going with a good band switch and all the Ham bands active and working, I decided this was going to be my sacrificial lamb and it has been modded up a bit.
Since the band switch was bad, this one has been monobanded. It has been mono'd on both the Input and Output side. 1 variable Input coil set to 10-15 meters with variable tune and load on the variable input coil, 1 output fixed tank coil with variable tune and load caps for the output. Also, the obsolete 120v bias scheme for cutoff has been replaced with cathode resistance for cutoff, and last the operating bias is using a variable Bias PCB bought off Ebay. The Bias can be adjusted from 3-30v and normal class AB1 bias is about 9.5v with stock plate voltage. Can't wait to play with this one. - Наука та технологія
Very clean layout. It seems more thought out. 😎
Clean layout, short connections, good components, that is why the Drake L4b and L7 are considered among the best 3-500z boxes made.
G'evening bro 🤠 . I've been a little sidetracked lately. My wife and I just moved 2600 miles from Idaho to Florida. On the flip side of that coin I just picked up a new to me Galaxy DX 959 radio & a 2 tube "no name" linear that was made by Chris aka Stickman outta MD before he passed away a few years ago & it should be plenty for what I want to do with this galaxy 🙃 ..
Sounds like a nice driver.
Question, I recently purchased what looks like a blackcat JB12 modulator, it has 8 diodes in the power supply and my issue is that the bleed resistors are getting very hot and want to smoke at only 60 volts. The caps and resistors are new and the tube tests good, any thoughts?
You have something very very wrong. The bleeders go across the High Voltage capacitors and should have about 350v across each bleeder/cap. They run warn but should not get hot. Do you have the right resistance (ohms) on the bleeders? On some Blackcat JB-12 and JB-150 schematics the bleeder resistor is mis-labeled. Th schematic has 10k resistors where the actual resistor needed is 100k. Using Ohms law, a 10K across that cap would pull about 11 watts which is what sounds like your problem is. Use 100k resistors, at least 2 watt, but I personally go with 3 watt flameproof resistors.
@@tramdr Would a 100K, 5W white rectangular ceramic resistor also work?
sure
@@tramdr FYI, I installed the 100K 5 watt ceramic high power resistors in the JB12, no smoke or discoloration but they do get hot?
Maybe a little warm but not hot. You got them in right, in series across each cap and not in parallel?
“Mono banded for 10 through 15 meters” you might get it to work on 11 meters but that’s illegal.
Doc, do you recommend grounding the grids on an L4B?
It will load for 10-15 meters including the Ham WARC 12 meter band. Yes, ground the grids directly, get rid of the 120 Bias, use a dropping resistor in the cathode and a diode string for operational bias and enjoy.
@@tramdr Thanks Buddy.
i have some really clean stuff.
You do? Cool, show it.