Yaesu FTDX-400

Discussion in '"Boat Anchor" & Classic Equipment' started by AF6LJ, Aug 18, 2011.

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  1. AF6LJ

    AF6LJ Ham Member QRZ Page

    We shall see what's going on tomorrow after chores.
    The Dishes never got done after dinner last night.
    Shame on Me. :eek:
  2. AF9J

    AF9J Ham Member QRZ Page

    You can usually get them off of evilBay pretty cheap. As you know I want one of the "evil" Swan 350s - a 350A, or a 350B. Yeah, I know, the 350s with the external power supplies run cooler, but I ain't gots much more room for radios & power supplies on the operating table! :)

    Swan 350A

    Swan 350B - ugly enough to actually look cool!
  3. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    now U got a radio that i DON'T HAVE!!! Have fun with it!
  4. AF6LJ

    AF6LJ Ham Member QRZ Page

    That was one of the radios I didn't see in your collection. I may need to tap some of sage radio knowledge of your's especially since I found an interesting problem that may be challenging, more on that later.

    As things stand now;
    I've opted out of placing another set of 6KD6s in the radio for now, instead I found that the 6LF6 is a reasonable substitute and has a tad more plate dissipation. They both are configured for EIA tube base 12GW and there are only a few minor differences in specs. The set of tubes nutralized on the first try using the same method I used on my Tempo-One. The radio does two hundred watts peak envelope power on forty meters. And could do more before four hundred watts DC input is achieved. Maybe two sixty on a good day with the line voltage is high, and the feedline is dry. :)

    We are not done yet though I have an expedition to go on tomorrow in the garage to see if I can find some more tube shields. There is also this matter of not being able to get the seventy five meter driver plate coil to properly peak.
    I have two theories on that problem;
    First I think the PA grid coupling cap may be going bad, it's a suite case mica cap and like the others in the PA compartment it looks like it spent more than a few hours in the heat.
    The second theory is I could have a weak 6GK6 driver measuring the cathode voltage is a good sign of the health of any tube that employes self bias as the driver in this radio does during transmit. Cutoff bias is applied during receive by way of the grid.

    I made a few measurements while composing this post and the 6GK6 cathode voltage is fine so is the cathode resistor. The Screen voltage is about 20% low which maybe okay more investigation is in order.

    Will post more late tonight or tomorrow.
  5. VK3ABN

    VK3ABN Ham Member QRZ Page

    I also have an FTdx401 but it is slightly different to the one in your pix. Mine has no AM function and no CW filter. The serial number is 302006 which may explain the difference. The unit is my original from the 60's and I haven't used it for years as I now use an FT7B. After having read your article I fired it up and, although the RX is reasonable, much as it was when I obtained the FT7B, there is no output from the TX. I'll look around a bit and let you know what I find.


    John (VK3ABN) Melbourne Australia
  6. AF6LJ

    AF6LJ Ham Member QRZ Page

    Look forward to hearing how you progress on that.
  7. AF6LJ

    AF6LJ Ham Member QRZ Page

    Making progress, I have managed to get full power on eighty and forty with a little careful alignment.
    Full output is defined as our hundred watts input to the PA. At that input power I see slightly over 250W out.
    It's a shame Yaesu didn't have access to 6LF6s when this radio was designed, as Steve pointed out there was a power war going on back then and the slightly higher ratings may have helped them out. :)

    The ten meter mixer coil was seized and had to be chipped out, thankfully I have coil slugs that fit those coils.

    With documentation being poor, one of my next steps will be to identify a few of the undocumented coils.
    Some located in strange places (pictures by tomorrow). For this task a grid dip meter will come in handy, god thing I have one. :) It beats trying to guess what they do. There are a number of traps located in the radio, I'm not surprised, both the 400 and the 560 use a somewhat odd conversion scheme.

    At this point I'm confident this radio isn't a lost cause, and I can go forward with confidence.

    More tomorrow.......
  8. AF9J

    AF9J Ham Member QRZ Page

    Way cool Sue! :cool:
  9. AC0VI

    AC0VI Ham Member QRZ Page

    These are the kind of threads that I love to see here, good job Sue!
  10. AF6LJ

    AF6LJ Ham Member QRZ Page

    I shall keep this one updated :)
    More news tomorrow.
    Stay Tuned.
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