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FR-101 Anti-Flicker Modification


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If you're on this page, you obviously own or are interested in the Yaesu FR-101 / FL-101.  There have been several requests regarding this modification on the Fox Tango Forum and we finally found it. This modification is nice because the FR-101 is more then just an amateur receiver. The FR-101 will tune all major shortwave bands and it can be annoying if the display sits there and flashes at you while you listen just outside of the ham bands or a short wave band. I will give you the instructions as I have them from Fox Tango Newsletter May 1978. It looks simple enough to do, basically cut one trace and add a wire to +5v supply. But don't rush off  to grab that Ginsu knife just yet!

Let me give you the mod first then I'll explain. A Letter was sent to Yaesu back in 1978 by a Fox Tango member as apparently in an earlier FT newsletter it was reported there was a KIT from Yaesu to do the Anti-flicker modification. That was incorrect, there never was a kit from Yaesu for  the Anti-Flicker modification.  So no kit is necessary nor  was one ever made to do this. The only thing you will need is a good knife, soldering station  and a very small covered piece of wire,  to do the modification.

As Per: FT May 1978 Page 32
The simple procedure to stop the flickering took less then 15 minutes to complete.
Here are the instructions: isolate pin 6 of Q3, SN7400, by cutting the pad on the
bottom of the board. Connect the pad (Not pin6) to the +5v supply at pin 14 of Q3.
**Now I don't know if you're confused after reading that like I was, so let me try and
simplify it for you. Because I was just a tad bit confused at first when they were referring
to the so called PAD, what pad.... I was thinking the pad at pin 6 of the I.C. that's not

First remove the four screws holding your display pull out each screw
half way at a time, if you try pulling one screw up too much while the others are
tightened down you can pop the "C" clamps on the other screws and the long screw
will fall out of the counter, I speaking form experience.

Unplug the Yellow coaxial cable with the RCA connector from the side of the counter
then carefully remove the TWO multi lead connectors holding the board in your rig.
Be careful and use a good light because there are two plastic clips that secure each of the
two black connectors, the black clips will break off if you're not careful. It won't be
the end of the world if you break one, as the plug will remain secure without them
but it would be nice if they remained in tack.

Pull off both top and bottom covers of your display board so you can see what it is
you're looking at from both sides. This display circuit board is PB1426A,
locate I.C. chip Q3. (Q3 is a type SN7400 I.C chip.)
It sits just forward of the large HC6/U crystal oscillator and the chip you are
looking for runs parallel with the rear of the counter.
Turn the display board over use your Exacto knife or a
sharp scalpel. Carefully cut the trace at pin (6) six of Q3
Don't cut it too close near pin six, cut the trace itself which lays
in the middle of the chip, see the pictures I posted in the
photos section of Yahoo Groups under the album labeled (Flickermod)
The trace you want to cut is shown at the tip of the knife. Cut this trace.
Then run a small wire over to pin (14) fourteen of Q3 from the PAD in the
middle of the chip on the trace that you just cut.
Don't run the new wire over to pin 6
The new wire you will install will run from the pad which sits
in the center of the chip over to pin #14 of Q3.
On pin 14 you will find a 2.2K ohm resistor in a plastic cover.
This 2.2 K ohm resistor at pin 14 goes directly to the 5vdc supply.
Double check your work under a magnifying lens for neatness.
Replace your covers, install the two plugs in the receiver, Don't forget
to install the Yellow Coaxial cable in the side of the counter or it will
not count. Tighten down all four screws, but not excessively tight.

The modification works, if you look at the photos you will also see the
display on my FR-101 reads 7.516 without the modification the display
would have started flashing once the dial hit 7.5 Mhz with an annoying flicker
indicating out of band operation.

I will try the same modification on the YC-601 counter and get back with you later
to see if it works. NOTE: If you submit a modification to the Fox Tango Forum,
PLEASE TEST IT FIRST and make sure it works. We do not have the luxury of having
a technical committee, so it would be nice to know without a doubt that all modifications
and projects work properly before you submit them to the forum.  It may just save us
a few headaches down the line.

Lastly: If you should need a replacement display lamp for your YC-601 counter or
your FR-101 display, the Nixi-Tube displays are still available from Yaesu of Anaheim
California under the current part number of G6090044 (Part number current as of  Jan. 2004)

Carol L. Maher W4CLM
Fox Tango International Web Page



Be careful when removing your counter, you will need to disconnect the YELLOW

coaxial cable with the RCA connector and two black multi-lead connectors.

Removal of display board PB-1426A from the FR-101 Receiver.



Cut the circuit board trace on PB1426A that comes off of Pin 6 of Q3,

It is best if you cut the trace in the center as shown in the photo

Cut trace from Pin #6 of Q3 going to the pad in the center of the I.C. chip.


On the bottom of the display board PB1426A you see the new RED

wire installed from pin 14 of Q3 to the pad at the center of the I.C. chip.

 Install a jumper wire from 5 Vdc at pin #14 of Q3 going to the Pad in the center.


Your display will no longer flash.


Without the Flicker modification the FR-101 & YC-601 display will flash once you go above 7.5 Mhz

Now we have a nice steady display which is no longer flashing or annoying to look at.

 All photos Property of Fox Tango International & W4CLM.





A little more information about your display

VFD Display Tubes

Digitrons !

NEC Vacuum Florescent Display (VFD) TUBES

NEC LD8062 & Futaba DG10S1

Commonly know as VFD tubes.

 The YC-601 digital display and the FR-101D digital receiver of the mid 1970s use the NEC LD8062

and the Futaba DG10S1.  The VFD NEC LD8062 was also found in some early four function calculators

 which may some day provide a source for spare parts for your counter should the supply of LD8062 dry up.

 We do have a few new pieces if you are in need of one, but they do not come cheap.

The same NEC LD8062 VFD display tubes being used in our YC-601 digital display

were also used in a Toshiba BC-1217 calculator in the mind 1970s

Toshiba BC-1217 calculator (Circ. 1974)




The Futaba VFD DG10S1,  10 mm high full indicator reading.

The DG10S1 is a digital indicating tube with 8 mm high numbers.

 It can represent the numbers 0 - 9, as well as a comma left above and a decimal point down right.

You may find this VFD in the Yaesu FR-101D digital receiver display unit.

Symbols: Numbers 0-9, comma announcement on the top right, decimal point right down
Number height: 8 mm
Diameter: 9 mm
Height: 35 mm
Base: 12 Wire cousin
Nominal Voltage: 15 V
Cathode stream: 2.0 mA

Jan / 2006  From Futaba

 Re: VFD DG10S1

This is a VERY obsolete part. I was not able to find a spec due to itís age. If you are looking for replacement parts, they just donít exist.

 If you are trying to fix a unit of some sort, Iíd first suggest that you check the power supply and drive signals because the VFDís are very robust.

If they havenít been broken, they may still be OK.  (Unless theyíve been on 24/7 for all these decades.)

 If you have any questions, feel free to call of email me directly.


Nick Price Senior VFD Engineer

Futaba Corporation of America

847 884-1444  Email:





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