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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

    Well today is the first day I have had a rest from my allergy, whatever it is, I think it's dog hair. :) The cleaning of this radio is taking longer than expected because of this but I was able to get back to it today. The front panel was removed and cleaned which provides more room to get at the main circuit board and clean and inspect parts. The front panel dial and assoiated peaces were cleaned and set aside.


    With the front panel out of the way cleaning can proceed.
    The VFO is going to have to be pulled so the gear train can be cleaned and re lubricated.
    There is a bunch of dirt and dried grease, more on that later.

    It looks like I'll be replacing the cathode current meter shunt.
    Looks like it got a little toasted.

    The shunt is the little component coming off Pin-2 of the tube socket there.
    Looks like a coil on a ceramic coil form, and you can see it got a little hot at one time.
  2. AF6LJ

    AF6LJ Ham Member QRZ Page

    Friday I disassembled the VFO gear train and cleaned all the peaces. There was a considerable amount of dried grease but nothing too hard to remove. the peaces were set aside for reassembly. I should take the time to make note of the over rotation mechanism used to protect the variable capacitor from damage. The VFO dial gear has two pegs that engage in a spring loaded latch that us used to limit rotation of said gear thereby stopping the variable capacitor before damage can occur. Note of the position of the dial gear at full capacitance was noted and a reference mark was made on the dial gear for the purpose of assuring the gear will be properly clocked at the time of reassembly.


    I know some hate split gears, they really are not so bad, if you have small hands :)
    If you don't have small hands now is the time when your boyfriend or girlfriend who does have small hands and mechanical aptitude really pays off. ;)

    The VFO was reassembled and a cotton swab soaked in 3 in 1 oil was wiped across the inner surface of each split gear before the sections were mated and clocked in order that the right amount of tension can be applied by the springs.

    The spacer for the dial gear, holes in both plates and the tuning knob shaft support / torque adjust... were dabbed with a small amount of grease. The dial gear spacer and the two gears were installed along with the tuning shaft were installed. The tuning shaft support was temporally installed. The gears are rotated until the referance mark is in it's proper location and the setscrews on the VFO shaft coupling are tightened.

    With all the gears in place the tension springs were reinstalled.
    The dial gear limiter arm is reinstalled next.
    The tuning shaft support was removed and the front gear plate was installed. Then the tuning shaft was permanently installed (knock on wood)
    The tuning shaft was rotated to make sure rotation was smooth.
    The drive works much better than it did when the radio showed up here. :)
    The last step before VFO installation is the installation of the spring that is a part of the dial gear rotation limiter.

    I can relate to how much some hate springs and reinstalling them let alone taking them out in the first place. With a peace of wire to hold one end and a pair of tweezers the spring went back in on the fifth try or was it the tenth, I don't remember.

    One other thing I forgot to mention; the VFO had one washer under the back mounting foot and two washers under the right side mounting foot. No doubt this was done to make it sit level. Anybody who has seen how an American radio of this vintage will find this radio rather unique in one aspect the chassis..........

    The chassis is not one single peace of punched and bent steel spot welded together at points with compartments mounted and sometimes spot welded to the top of it (PA VFO etc...) this radio's chassis is made up of discreet peaces each side of the bottom apron is a separate peace. The power transformer and filter choke, caps and VR tube sit on a plate that is screwed down with screws and star washers. the right hand side of the radio chassis, the part that contains the bandswitch, preselector, and associated components is a plate screwed down the the chassis frame also., all the shields on the underside are held in with screws and star washers. The most complex peace of sheet metal in the radio in terms of bends is the PA cage. Something a high school student could visualize and bend up in metal shop. I don't think I would have used star washers on the printed circuit board, that is more of a flat washer, split washer combination application.
    I did find several of the screws holding the main PCB in place loose.

    Stay tuned more to follow.
  3. KC2TAU

    KC2TAU Ham Member QRZ Page

    Your patience and attention to detail are an exceptional example. I am looking forward to seeing the finished product. Keep up the great work.
  4. AF6LJ

    AF6LJ Ham Member QRZ Page

    Right now I am on another project for a friend. I will return to my work on this after the first of the month.

    If you haven't seen it yet go look at this thread, it concerns something I found I have to correct before I power the FTDX-400 back up.
  5. KM1H

    KM1H Ham Member QRZ Page

    Sue, if you need some resistance wire for a shunt let me know the value and I'll send some. I have several different Ohms per foot.

  6. AF6LJ

    AF6LJ Ham Member QRZ Page

    Thank You Carl;
    I'll do that as soon as I determine if it is in fact damaged or just lightly toasted. :)

    I plan on putting my ammeter in series with the shunt to see how close the the cathode current meter reads.

    I have the voltage regulator mod to do yet...
    As soon as I get another project finished I'll be back on it.
  7. AF6LJ

    AF6LJ Ham Member QRZ Page

    Well now that Thanksgiving behind us I can settle down to some serious work on the FTDX-400.
    Today I did the voltage regulator mod, so that the radio will be safe to power up the next time that happens.

    An orange wire was added to Pin-5 of the VR tube socket...
    Then it was routed up to R-49 one of two wirewound resistors mounted on the left chassis wall.
    The small orange wire was removed and in it's place the new wire was attached.


    After that the old orange wire is followed over to where it resides on the main PB board sheer it is snipped off.
    The reason this mod is done this way has to do with the routing of that small orange wire seen in the above picture connected to pin one of the VR tube. That wire actually connects to all the loads this voltage regulator feeds. So if we remove the short orange wire and replace it with a longer orange wire going back to Pin-5 of the VR tube we then connect the voltage source to the VR tube through that pin. Now when the tube is pulled from it's socket or develops an intermint connection it less likely to float up to it's source voltage. The one thing I will do in this case is also ground pins four and two of the VR tube they are redundant cathode connections and should also be connected. to further ensure that the VR tube circuit won't fail.
    (Kick me I just thought of that)

    For a better view of where this is......
    The skuzzy stuff on the PCB is ether the flux left on the board or some kind of conformal coating. I think it's flux. because the board has a solder mask on it. Denatured alcohol makes it look that way, you can wash it off but it takes large quantities of solvent and I've better things to do than chase that stuff all over the radio.

    While I have the diode board up, it's a good time to replace all the diodes with new ones since in the very near future there will be new caps in the power supply.

    Stay tuned. :)
    Last edited: Nov 25, 2011
  8. AF6LJ

    AF6LJ Ham Member QRZ Page

    One of the reoccurring themes in this radio and most likely others of of the FTDX family of the sixties and early seventies is "when all else fails throw parts at the problem". When you look at the power supply this is vary apparent.


    C-95 is in paralell with one section of C-603. I have decided that is going to get replaced with a single 100 microfarad cap, which will unclutter the underside of the radio a bit. C-92 will be replaced also since they make much smaller electrolydics these days. Three section electrolydics are not that easy to find these days but I am going to look for one to replace C-603 with.

    The diode board looks a whole lot cleaner now.

    Resistance checks all indicate everything is good and when I get the front panel back on (very soon) I will be able to turn on the radio with a high degree of confidence all will be well.

    I'll get the radio back together and in January I'll make a another parts order from Mouser or wherever pending the location of a suitable replacment for C-603.

    Counting the other irons I have in the fire I should have the FTDX-400 back together before the New Year's Day Net.
  9. KQ0EA

    KQ0EA Subscriber QRZ Page

    Wonderful work!
  10. W5WPL

    W5WPL Ham Member QRZ Page

    WOW You forgot more about this stuff than I'll ever know.
    Very impressive Sue.
    Thank you for sharing this with us.
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