You never know what is inside...

Discussion in 'Amplitude Modulation' started by W7TFO, Mar 20, 2021.

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  1. KC2ZFA

    KC2ZFA Ham Member QRZ Page

    sand ? is that an example of early solid-state technology ?
    WQ4G and WZ5Q like this.
  2. W8KHK

    W8KHK Ham Member QRZ Page

    A recent quote from you, Dennis: "I still can't bring myself to mix silicon & tubes, just me."

    It appears that has just been disproven!
  3. W7TFO

    W7TFO Premium Subscriber QRZ Page

    LOL, OM.

  4. WZ5Q

    WZ5Q Ham Member QRZ Page

    Yes, I was pleased to see that auxiliary winding when I got the big reactor. I shouldn't need to modulate the RF Driver as I am using a pair of low mu Triodes in Push Pull for the RF Finals and they tend to do very well at modulating positive peaks with excellent modulation linearity. If I have issues and do need to modulate the RF Driver Stage, then the Push Pull 35TG's will be using around 250mA @ 2Kv so I think the auxiliary winding should handle that with no issues.

    The degreaser and epoxy was my plan. I did not think about wrapping the lead with extra insulating material. Thanks for that idea. I have some thick mil Kapton Tape that might do the trick, or maybe something Teflon.

    Yes, that was my intention. I do not like to ground the core of old Mod Iron or Reactors due to the age of the winding insulation. It seems that is the most common failure with the older Iron, leakage or shorts from the windings to the core to ground. Yes, isolation from ground is dangerous, but I feel it's necessary for the preservation of the older Iron. A proper high voltage lockout string, placards, a Jesus Stick, and Common Sense help with that danger.
  5. K5UJ

    K5UJ Ham Member QRZ Page

    Same here. I never subject old iron to rack mounting, instead letting it rest on ceramic floor tiles. Any operator who's dumb enough to stick his hands into a live hot rig should stick with plastic radios & solid state leenyars.
    K4KYV likes this.
  6. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    For those who are paranoid about forgetfulness or someone else being injured or killed by touching the floating transformer in the highly unlikely event that it just happened to have recently developped a short to core, affix a conspicuous reminder directly to the piece of iron, not to touch it because it may be hot to ground. Chances are, floating it will prevent the insulation breakdown that would have made it dangerous to touch in the first place.

    Another thing that may happen, which would not be particularly dangerous per se, is that due to the residual capacitance from the transformer case to ground (if the insulation is in fact really good), it may accumulate enough charge to give someone a jolt if they happen to brush against it. The worst that would likely happen would be to startle the person and cause them to reflexively jerk back and damage something or injure themselves. It would certainly serve as a reminder that "hey, this thing might be hot with HV".

    That has never worried me, since I always treat floating transformers and other components exactly as I would if the case were hard-wired directly to the +HV, and try to avoid whenever possible, having to insert a hand inside the cabinet while the +HV is on. That's another reason why all my transmitters completely kill the +HV during stand-by periods, unlike some commercially-made and homebrew transmitters and leen-yars that keep the full +HV on all the time, even in receive mode.

    I have seen photos of the interior of high power commercially-built broadcast and communications transmitters that showed large transformers and reactors mounted on tall ceramic stand-offs.
  7. KA4KOE

    KA4KOE Ham Member QRZ Page

    Well, sand is mostly silicon. Good call!
  8. K0IZ

    K0IZ Ham Member QRZ Page

  9. W7TFO

    W7TFO Premium Subscriber QRZ Page

    No printed circuit boards there.

    Nor Poly-chlorinated biphinols.

    Mineral oil.

    K5UJ likes this.

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