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Recent content by Shockwave

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    Maco 300 pumpkin face 1 driving 4 8950 Problems with red plating and have to constantly retune after one minute of no keying

    I've seen that happen with a few of the old red door knobs that they used in Heath kits. There're not as good as the tan colored ceramic ones. I'm sure they didn't use anything quite as good here either. Not that it's required.
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    Maco 300 pumpkin face 1 driving 4 8950 Problems with red plating and have to constantly retune after one minute of no keying

    "Constantly needing retuning after a minute of no keying", sounds like a fixed value capacitor across the tune or load, is shifting in value as it heats. Not even sure if there is one padding that variable, but it is one of the few things that cause that symptom.
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    TX Star 250 dx SWR ? (Something lost it's value ?)

    You're not going to like the answer. Your amplifier is oscillating. That is a typical problem with smaller Texas Star amplifiers, due to their bias circuit design, sharing an RF contact on the relay.
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    Lets talk about replacements for 6lf6 tubes

    No, in fact I've seen one brand like RCA, produce both the single and double versions.
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    Lets talk about replacements for 6lf6 tubes

    Those 3 amps of filament current, also give the 6KN6, a whooping 1.5 amps of peak cathode current! It has the widest oxide coated cathode of any sweep tube. I bought sleeves of these tubes years ago for $4.99 per tube. I've been using them ever since in every application from a single tube grid...
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    Either amazon transistors suck, or I am an idiot...

    I think the problem has to do with the DC biasing on your first single-ended transistor driver. Since it is single-ended and NPN, I don't think it should be powered from the same split rail Supply that is feeding the complementary symmetry outputs. If I suspect what is happening is correct, your...
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    What's inside a 4CX250B tube?

    Not a good idea to crack that BEO ceramic insulator. Any dust particles from the cracked insulator, are highly toxic if inhaled.
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    High Voltage hijinks, National NCL2000 style.

    With sockets changed and bias reset, it's not hard to get this amp to run inexpensive 4X150A / 7034 tubes. About $50 each for NOS. Even though this version of the tube has 150 watts less dissipation than the 8122, the anode radiator is the same size and there is no noticeable drop in output...
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    Stryker sr-94hpc

    You'll need a real peek reading watt meter in order to see the 45 watts PEP. Output power is not the problem with that radio. Being able to receive anything through the noise in the mobile environment, is the problem. The radio has no noise blanker, just a mislabeled automatic noise limiter.
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    Golden Falcon Base Amp - 10 tube

    Use a volt and ohm meter, to start checking for filament voltage and open filaments in the tubes.
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    FrankenMaco, back from the undead.

    I've been testing everything from 4CX250B, to 8877 on and old Precision tube tester, with an external socket board and a 15 amp filament Transformer. With a bigger filament Transformer, you can test a 10,000 tube. All that's required is a known good tube, to determine the correct load value. If...
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    Palomar 300A questions

    Nomad has you on the right track. This has nothing to do with the switch, it is the relay this switch is operating. This relay may come back to life with use or flipping the switch a bunch of times. They are difficult to remove the cover and clean without damaging.
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    Clean Texas Star Sweet 16 for sale.

    I'm glad everything worked out as expected, and everyone is pleased. Nice work on the restoration.
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    New 32 pill is a dog :(

    This is not a correct diagnosis. When bias does not turn on with a transistor, it works under less stress in class C.
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    Clean Texas Star Sweet 16 for sale.

    My pleasure Ranch. Glad to see it go to someone who appreciates its 1990, all original factory work. Please let me know once you've had a chance to test it. I want to insure it arrived in good operating condition, as well as physical condition.