Need Info on Yaesu FTdx-401 Series Radios

Discussion in '"Boat Anchor" & Classic Equipment' started by AF9J, Sep 24, 2011.

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  1. AF9J

    AF9J Ham Member QRZ Page

    I went to a little swapfest this morning to pick up a Lakeshore Industries Phasemaster II (mid 50s SSB transmitter, that was made in my hometown of Manitowoc, WI). While I was there, I spied a Yaesu FTdx-401 at one of the tables. As you may know, Sue's FTdx-400, used to belong to me, so I have a bit of a soft spot for these older Yaesus. Throw in the fact that I'm interested in a slightly higher powered, classic radio, for casual ragchewing, when condx. are only so-so, and I was interested in it. Well, I bought it, after haggling with the guy selling it, for $140 (he didn't want to drag it back home with him, since the 'fest was winding down, so he accepted my offer). I've fired it up, and like did with my Tempo One, it's baking in receive mode on the radio table. So far so good. The T/R relay was sticking at first, making receive a little weak, but exercising the relay a few times, has improved things quite a bit. Ditto for the band switch, and the AF Gain/volume knob. The receiver has great audio, and is pretty sensitive. I need to get my hands on a manual for it (the guy who sold it to me, took my address, and told me that if he could find the manual, he'd mail it to me).

    Here's where things get weird. I've known about the FTdx-401 for a couple of years (I almost bought one off of eBay back in 2009). I've always been under the impression that they were SSB/CW rigs only. The BAMA and Fox Tango group FTdx-401 manuals confirm this

    FTdx-401 photo

    But, while the front panel on mine says FTdx401, its mode switch is like the radio that was its successor - the FT-401B, in that it also has AM capability.

    FT-401B photo

    Those of you have way more experience with these FTdx era rigs - do I have a transitional (between the FTdx-401 and the FT-401B) rig? I'm trying to figure out which manual to download (FTdx-401 or FT-401B) if the guy who sold me the radio, can't find the manual.

    BTW, here's the link to an FTdx-401, that looks like mine (it's a "rights reserved" photo, so I can't directly link it)

    Attached Files:

    Last edited: Sep 24, 2011
  2. VE1PEW

    VE1PEW Ham Member QRZ Page

    I have the same radio you have. The manual that came with mine doesn't show am on the mode selector but the switch is there for it. If you have trouble finding a copy of the manual let me know. I can photocopy mine and mail to you. I also have the full schematic with my manual.

  3. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page

    The FTDX 401 is a bit rare. It was sold between the FTdx-400X and the FTDX 560 in 1969 and 1970. It will run 125 watts of controlled carrier AM (that's pushing it) and it tunes up exactly like it's predicessor. Don't know why the manual doesn't show an AM position on the mode switch but tune it up and you will see.

    Very nice find by the way.
  4. K4ZOT

    K4ZOT XML Subscriber QRZ Page

    What memories the FTdx401 and all the 1969/70 Yaesu rigs bring to mind. I bought my first new radio after college in 1969. It was a rather rare FTdx560. It had 500 watts and was very much sought after by the CB crowd. The mod to AM required cutting one wire. If I remember correctly it had a very short life on the radio market - like a year before the FCC banned it.

  5. AF6LJ

    AF6LJ Ham Member QRZ Page

    Can't believe I missed this thread back in September.....
  6. AF9J

    AF9J Ham Member QRZ Page

    Hi again people! Basically through over the phone discussions, Sue and I sussed out this radio. Through some further research, I found out this is a transitional radio, that was made before Yaesu introduced the FT-401B. It's often called an FTdx-401B. Its circuitry is the same as a standard Plain Jane 401's (it took not only going through the schematics of an FTdx-401, but also the schematics for Sue's FTdx-400, and the FT-401B [the only other radios in this series that had AM capability], to confirm this), BUT, it has a small additional PC board (mounted to the front panel behind the meter, with a long standoff down to the main circuit board for support), that seems to be for the purpose of providing AM capability. Neither the FTdx-400, nor the FT-401B have this circuit board. So, it was probably a cheesy, quick and dirty add-on to give the FTdx-401, AM capability, without having to make too many revisions design and production-wise, to the radio.

    If you remember Sue's thread asking why Yaesu wired up the voltage regulator tubes for this radio series in such a dumb way, it was based upon my FTdx-401. Basically, after cleaning the radio internally, and baking it it for a few days, to see what would fail, I fired it up for the local Vintage SSB net. As I was finishing tune-up (I had good plate current from the finals), my receive audio died. Ditto for current to the 6KD6 finals. Cleaning the relay contacts (they were a bit on the dirty side) didn't help. Further trouble shooting turned up that R49 (a wirewound resistor) failed. R49 leads directly to the voltage regulator tube, so what probably happened, is that a piece of crude probably got in the regulator tube socket while I was cleaning things up in that area of the radio. When I was tuning up, voltage went up. The crud arced, and a spike took out R49, due to the voltage regulator tube being wired in a stupid sort of parallel manner, instead of in series, like it should have been for that voltage section of the circuit. Everything else checks out fine - it's just that one resistor that failed.

    Since work is closed until Jan. 3, I plan to replace the failed R49, and re-wire the regulator tube, to take care of the wiring glitch, I hope to have the radio on the air in time for this year's New Year's Day Zed Net.
  7. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page


    AF9J you want to sell me your rig, you don't know why but you must sell it to me......You must sell it, you must sell it.
  8. AF6LJ

    AF6LJ Ham Member QRZ Page

    That's Cute. :)
  9. N4TG

    N4TG Ham Member QRZ Page


    I bought a new FTdx-401B From Freck radio in Asheville NC - will have to look at my logs to see when I bought it. Also had the remote VFO. Sold them in about 1984-85. The only problem I had was a bg wire wound resistor in a voltage regulator circuit burned up - sounds like the same problem here.

    Bought a FT-401B on ebay a while back but don't have it on the air yet - was not packed correctly and the input 120VAC fuse holder was broken off in shipment. Have a replacement holder but have not put it in.

  10. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page

    Thanks but did it work??
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