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Henry 2K4, checks B4 powering it on?

Discussion in 'Amateur Radio Amplifiers' started by W0GUS, Jan 13, 2019.

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  1. W0GUS

    W0GUS Ham Member QRZ Page

    Greetings Ladies and Gentlemen,

    I recently got a fantastic deal on an old Henry 2K4. What a monster!!!
    It needs a new chimney for one of the tubes, and I have no idea if the tubes are good or not.
    (not even sure what brand they are, they are not even from the same manufacturer I think)

    Everything in the RF deck looks very good, except for tarnish on the silver plated components.
    Everything in the power supply section looks good as well. Instead of the usual 4 or more filter caps
    this thing has one massive capacitor. It looks good, no leaks or anything.

    Now, since I don't have a variac, let alone one for 220V, do you think it's safe to just plug it in
    and turn it on? It hasn't been powered up for "years" according to the previous owner.
    It has a lot of protection circuits in line, so if there is a short or something it should NOT even power up
    I wouldn't think, but I don't know much about Henry amps other than they look like their built to
    last forever.

  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'd power it up without the tubes installed, first. Make sure the anode caps for the tubes are not near anything and can't touch anything, and only power it up with the covers in place. If the amp has a CW/SSB switch, power it up first in the CW position which should be a lower voltage tap on the HV transformer. If that all seems okay, turn it off, switch to SSB and turn it on again. The plate voltage meter should indicate and let you know the power supply is working. Check to see the blower is spinning smoothly and pumping air up past the tube sockets (you can feel the air even through the top cover).

    Turn it off, wait for the plate voltmeter to drop to zero and install the tubes and chimneys, re-seat covers and see what happens.

    One weak link in a lot of the old Henry choke-input amps is the choke and its resonating capacitor which is wired across the choke. The big oil-filled filter caps can last a very long time.
  3. AD6W

    AD6W Ham Member QRZ Page

    Everything WB2WIK said, plus this: if it has been stored anywhere it can absorb moisture, that choke will have moisture in it and will probably fail. I had one do this that was a good working amp before I stored it in a a garage a few weeks and then tried to bring it up. Best to remove the choke and bake it first, or at least store the amp in a warm dry room for a few weeks in before hitting it with high voltage.
  4. AC0OB

    AC0OB Subscriber QRZ Page

    I still have a 2K-4 and when I bought it it had originally been stored for many years without being powered up.

    The original Amperex tubes lasted for years.

    I would seriously consider an inrush protector such as the before turn-on.

    The RF choke for the Final's is mounted horizontally so I doubt it will have any moisture problems, but dust and fuzz bunnies can be problematic with about 3500 volts floating around.

    Clean all dust with a vacuum cleaner and as Steve said, make sure the blower rotates freely and supplies enough air. One thing i discovered early on is that there are two covers over the RF deck that can reduce air flow. I cut out a larger opening in the aluminum cover closest to the tubes to increase air flow.

    The power supply can be improved by replacing it with capacitor filter system which also reduces a lot of cabinet heat.

  5. W0GUS

    W0GUS Ham Member QRZ Page

    Thanks for all the information! I looked at the Ameritron inrush protector, but it is rated at 10A/240 after inrush protection and the specs I found on the 2K4 state 15A/230V which I assume is maximum current draw. I do not intend to drive it that hard so the device will probably work OK for me, yes?

    The blower spins freely, and I have vacuumed out all the cabinets and given them a good blow out with compressed air. The larger opening you cut out, was it just round enough to open up the chimney output or did you make it larger than that?

    Sorry for all the questions, but I'd like to get this right the first time. I am really looking forward to getting this wonderful piece of history back on the air.

    73 de WØGUS
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I wouldn't bother cutting the exhaust opening of the interior cover plate any bigger; that might be a feel-good thing, but 3-500Zs cool almost entirely by radiation and not convection and the forced air blown through the chimneys is almost entirely to cool the filament pins under the sockets, and a little bit to cool the anode seal (top pin) -- it only takes a trickle of air to do this exactly right. The glass interior elements of the tubes don't benefit in any way from air cooling, and the glass used is good to >3x the pin seal temperature rating, so it doesn't really benefit from the air, either.

    I'm not sure what the inrush protector would do; the 2K-4 already uses a heavy-duty relay to power the primary and has a choke input filter which limits inrush current quite a lot; I wouldn't bother with this.
  7. W1QJ

    W1QJ Ham Member QRZ Page

    I agree no in rush needed with choke input.
  8. AC0OB

    AC0OB Subscriber QRZ Page

    The tubes are cooled by both radiation and forced convection (blower).

    The top cover plus the grill closest to the tubes do impede air flow.

    I cut the opening slightly larger than the combined area of the chimney openings. For the top cover I replaced it with a perforated decorative bronze grill and also cut round holes in it above the chimney openings. Since I have two curious grandson's, I took 1/16" stainless screening and covered the holes with it and used 6-32 brass screws and nuts to hold it in place. Those screw-nut combos also had Loctite applied during assembly for obvious reasons.

    Good air flow through the 3-500Z bases is necessary to keep the filament pins from overheating and crystalizing the solder connections just below the ceramic tube sockets. (Been there for a re-soldering job:eek:). Any resistance to flow from above results in a back pressure that reduces total air flow.

    In addition, recirculated hot air is kept to a minimum.

    Last edited: Jan 15, 2019
  9. W0GUS

    W0GUS Ham Member QRZ Page

    OK, something is just not right here with this thing. I tried checking the big 100 watt resistors but they all show open, and I get nothing when I try and power the amplifier. No clicks, no fan, no nothing.
    Do I have to remove the resistors from the circuit to check them?!?
    Both fuses check good, and I have 240 volts at the terminal strip on the bottom of the amp, the magnetic interlock on the PS cover works, and the two fuses check good, and the RF cover is on and the shorting strip for the HV is not making contact.
    What would keep the amp from even trying to power up? ??
  10. W0GUS

    W0GUS Ham Member QRZ Page

    Ha ha ha ha, the joke is on me! ID 10 T error.
    The switch on the front panel which I thought was an Operate/Standby switch is the On/Off switch.
    There is no standby switch I guess. Anyway a good 3000VDC show on the meter, fan runs strong,
    I'll put the tubes in tomorrow and apply a bit of RF into my cantenna and see what happens!!!
    KA5UUN likes this.

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