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Reintroducing the Yaesu FT-75 / FT-75B (Circ 1971)

Oh do you remember these?

The Year is 1971, The President of the United States is Richard M. Nixon and the Vice President is Spiro T. Agnew.  Cigarette advertisements are banned from American television, the Ed Sullivan Show goes off the air,  the Apollo program: Apollo 15 astronauts become the first to ride in a lunar rover and women gain the right to vote in Switzerland.

And the Honda Z600 sedan was invading our shores world wide

The Honda 600 was the first "mass market" car sold by Honda. The N600 sedan was introduced to the US market in 1969, and the sportier Z600 coupe followed in 1971.  The Honda 600 sedan (N600) and coupe (Z600) are small cars - just over 10 feet long, and weighing about 1300 pounds. Powered by a two cylinder motorcycle engine with 36 cubic inches and 36 horsepower.

OH Yeah, we were talking about Radio weren't we?

So lets see if we can do a little mobile operation with the FT-75

Photos from the original Japanese FT-75 owners manual.

The FT-75 is show going mobile, under the dash in the Honda Z600

So what exactly is the FT-75?

Introduced in 1971 as a compact amateur band transceiver that would operated from 3.5 to 28 Mhz SSB and CW modes.

The FT-75 is a hybrid high frequency transceiver that sports a single 12DQ6B final amplifier tube driven by the popular 12BY7A driver tube as found in many of the Yaesu products during this time. Specifications for the FT-75 vary because it was originally introduced in Japan to meet JARL specifications the single 12DQ6B final is rated at 20 watts. However later the transceiver was reintroduced as the FT-75B sold elsewhere in the world the FT-75B is rated at 30 watts P.E.P input power low or 100 watts input power if it is set up for high power by use of the matching FP-75 AC supply or the DC-75B mobile supply.  In order to achieve the higher power over that of the original FT-75 the new "B" model used two 12G-B7 final amplifier tubes.  The FT-75 transceiver is an interesting piece of equipment in that it is crystal controlled, while at the same time it uses a VCXO front panel control.  For those of you too young to know what exactly a VCXO is; it's called a Variable Crystal Oscillator. Thus would the VCXO will allow for a frequency shift of several KHz above and below the actually crystal operating frequency frequency, much like a fine tune or ~RIT~ Receiver Incremental Tuning control found on modern transceivers.

Another unique feature of the FT-75(B) mobile transceiver is that there are no final amplifier tuning controls that can be accessed by the operator from the front panel while driving, other then the VCXO on the front panel there are a bare minimal of controls for volume and squelch control.  The transceiver is a hybrid, part solid state with tube type final amplifier stage, the tuning controls (Loading and Plate tune) are accessible from the rear panel and and once set should be left alone.  One advantage of the FT-75(B) is that it is pre-tuned and allows for quick QSY, has an effective noise blanker and squelch circuitry.  This makes it an ideal transceiver for simple and safe mobile operation as well as for home station use.

FT-75 Shown with the FP-75 power supply

AUTO-TRANSFORMERS
 For 100, 117 or 240 Volt, 60 Hertz Applications

Although primarily sold as a compact mobile transceiver, the FP-75 desk top power supply was sold as an option to use the transceiver in base station operation.  One thing the casual user in the United States should be aware of is that theFP-75 power supply that was originally intended for use with the  FT-75 transceiver was not intended for export, thus the power supply is set up for 100 VAC / 60- CPS  that is standard house current in Japan.

FP-75 AC Speaker Power supply   Note: The 100 VAC primary winding as used in Japan

In order to over come this problem and still use the original 100 VAC transformer installed in the power supply from Japan, I wired together two transformers to make what would resemble a make-shift auto transformer.  I was lucky in that I had a disassembled Yaesu FP-4 (12 VDC) power supply and saved the transformer.   After all that is what hams do, save STUFF! So the old transformer finally came in handy for something.  The FP-4 was an export version power supply from Japan, as such it had more then one tap on the primary side of the transformer, 100/117/220 VAC windings. Using the transformer for its primary only, applying 117VAC to the typical primary winding that would be used in the United States, yielded not only the secondary AC voltage of 20 VAC (NOT USED) but the primary side would also yield all the other voltages as per the primary winding usual inputs such as 100VAC and 220 VAC, that could now be used to step up or step down our voltage.  Special transformers are usually called  AUTO-TRANSFORMER and can be used for this type of application, the drawings below have been provided to give you a BASIC idea of my the fixed primary tapped auto transformer that I used and it's comparison to a Variac or variable autotransformer.

Much like a Variac, but using only the fixed primary windings of our transformer we

 can effectively drop our voltage to the required  100 VAC/60 cps as it was used in Japan.

The secondary winding of our transformer is not shown however it still exists but will not be used.

Auto-Transformers
 For 100, 117 or 240 Volt, 60 Hertz Applications

Auto-transformers are frequently used to convert local power line Voltage to some other Voltage value needed for a particular piece of equipment.  Most often, this conversion is from 117 Volts to 240 Volts, or 240 Volts to 117 or in this case to the required 100 VAC.  Unlike an Isolation transformer, auto-transformers use common windings.  Such transformers like this are often employed in custom designs or when converting industrial / military equipment between various operating voltage systems. In our configuration shown above a 3 amp fuse was installed between the 1st and 2nd transformer to protect the power supply should we have any high currents develop in the additional transformer windings.

It's hard to believe but this is how I found C3 of the high voltage power supply filter capacitor hanging loose inside the FP-75.  Apparently the H.V. filter capacitors developed a problem at some time in the past and someone decided to replace it.  The capacitor was hanging loose and the wiring was crimped NOT EVEN SOLDERED.  Also found the HV wiring to the power transformer secondary twisted around the transformer contacts and those were not soldered either, unbelievable.  So for God's sakes gang, if you're going to do a repair take your time and do it right and above all solder your connections.  Especially when a repair involves high voltage, do it neat or don't do it at all.

First order of business was to make the power supply safe to use so we removed the jury-rig capacitors.  Cleaning up the basic power supply would make it safe to use again, not blow fuses or be of a danger to the operator.  Later we installed the second transformer in the auto-transformer configuration as explained above.

Our power supply is now fully repaired with a second transformer installed using the 100VA winding of the first transformer feeding it over to  the original Japanese transformer with a 3 amp fuse for protection between the 1st and 2nd transformer.

Show side by side the FT-75 and FP-75  with cases removed (right)

FP75 Schematic

This FP-7B was recently sold on EBay with the mobile DC-75 multi-vibrator power supply.

FT-75 VXO Frequency Card for your convenience

Now here's a net little chart for your FT-75(B) frequency listing.   Most likely if you own an FT-75(B) this little gem is long gone! This card came in a little plastic protector and is originally the size of a credit card to carry along with you in the mobile so you could keep track of what frequencies were installed in each channel location.  If you're an FT-75 owner you might find this a to be a handy little chart to print out list the channels / frequencies you have installed in your transceiver on this chart.  In the VXO box, put in the number as shown on your VXO front panel for the exact crystal frequency.   The VXO will allow you to shift the crystal operating frequency up and down a couple of kilo hertz, this way you will know exactly where you are on the band.   The variable crystal oscillator shifts frequency of crystals slightly and the markings on the front panel do not have any frequency significance.  The original credit card sized chart I have here has a place on the back of it showing the serial number of the rig as well as a place for  your call and name!  Leave it to Yaesu to come out with all these little goodies, along with a portable log book and alignment tool that came with the rig to adjust the PA stage.  And several  little plastic  boxes to hold your extra crystals.  All in all, with all the original advertisements and documentation that came with this transceiver it was a great find for the Yaesu collector.

Lets take a closer look inside the FT-75(B) transceiver

So compact, so sweet!  They don't make them like the use to!

A look under the bonnet of the FT-75, Top cover removed.

Power amplifier stage upper left corner.

FT-75 PA cover removed reveal the single 12DQ6B PA tube and 12BY7A driver.

Note the tube clamp on our horizontally mounted 12DQ6B final amplifier tube, used to hold the tube in place for mobile operation.

  A closer look into the PA shows the final amplifier and the tuning controls

(Loading and Plate tune) accessible from the rear panel, and once set up they should be left alone.

Still installed and in good condition the original factory installed Toshiba tubes.

FT-75 Final Amplifier Compartment single 12DQ6B

12DQ6B installed in the FT-75

FT-75B Final Amplifier Compartment (X2) 12G-B7

  12G-B7 installed (X2) in the FT-75B

Looking from the top side of the transceiver we see the Transmitter Coils, Receiver RF coils for each band.

RF front end circuitry, Audio Amplifier and 9 VDC regulator.

A few points of interest here is the AN212 audio amplifier IC is installed in a metal TO3 type transistor case. This particular audio amplifier was later replaced by the AN-214 flat pack audio IC that we commonly see in most Yaesu products produced through the 1970s.

  The AN212 audio I.C. was also used in the early FT-2 Auto VHF FM transceiver

The AN-214 audio I.C. was used in the later model FT-75B replaces the TO3 type AN212

PB-1149 ~ Looking from the bottom side of the transceiver we see the IF board, note the I.F. frequency of 5173.9 KHz and the use of the SSB crystal filter XF-51A, I don't believe this particular I.F. center frequency and crystal filter were used in any other Yaesu product.  On this board we have our I.F. amplifier stages for our receiver, squelch amplifier, AGC amplifier, and transmit I.F. stages along with our SSB crystal filter XF-51A as shown above.

PB-1152A Microphone amplifier and 1st SSB oscillator circuitry.

It is interesting to note how closely the construction of the Yaesu FT-2 Auto VHF transceiver (Circ 1972~ left)

 looks in comparison similar to the FT-75 (Circ 1971/72) of the same time frame.

I was lucky in that the original owner of the FT-75

saved all the original Yaesu advertisements from 1971 shown above

The FT-75 can be used with the option FV-50C VFO.

The FV-50C VFO was also an option for the FL-50 / FR-50B HF combination.

It's funny to see the cigarette lighter and tobacco product in the advertisement.

Download the FT-75B owners manual PDF format here.

Download the FT-75 owners manual here (Original Japanese) **not yet uploaded**

One of the more interesting things about this acquisition was all the documentation and paper work that came with the transceiver that was originally purchased in Japan.   Now you might not be able to read Japanese but you still might find this interesting.  The "Yaesu Musen Journal" December 25, 1971 carried a review for several new Yaesu products, one of the products was the introduction of the FL-2100 linear amplifier and the FT-75.  Down load the FT-75 review here, it's in Japanese  it's still fun to look at even if you can't read it. 

Finally in an effort to teach a little along the way,  I always like to throw in a something interesting about the Japanese language when I can find it.  I've already pointed out in past on other club web pages that the word "MUSEN" is the Japanese word for wireless. So it's was at one time known as Yaesu Wireless Company, today the company is known as Vertex Standard.  The commercial end of the company has always been known as Vertex Standard, but even at this time the company still retains the name of Yaesu for it's line of amateur equipment.

An interesting thing about the Yaesu Musen Journal No. 8 is the date.  How could I be sure it was printed in 12/25/71~ ? Well the back cover of the Journal shows the date in Japanese, but you can't find the year 1971 any where, at least it's not written in a way that westerners would recognize it.   You will see several numeric characters on the back page of the Journal and you'll recognize the numbers 12 and 25.   The Japanese character GETSU is shown right next to 12 and this is the character for the month, the Japanese character NICHI is the character for the day and is right next to the number 25 indicating the 25 day of the 12th month.  But here's the real challenge where is the year?   You see 46 ?  Humm.. but 46 what?   The Japanese use a numbering system for their traditional calendar that is completely different from that of the Gregorian calendar which is the most widely used calendar in the world.  The traditional Japanese calendar however is based entirely on the reigns of its emperors.  So when looking on the back of our Yaesu Journal we see number 46, this indicates the 46th year in the reign of Hirohito taking the official name of Showa it means ("Enlightened Peace") the Showa reign lasted for 64 years until 1989.  After the death of Hirohito in 1989, Hirohito was succeeded by his son, the Emperor Akihito which then began the reign of Heisei.  If we look at the back of the Yaesu Journal it shows the the number 46 next to the Japanese character  (Nen or Toshi) indicating year. Thus the Journal was published December 25th in the 46th year of Showa or (1971) for more information on the Japanese calendar see: Japanese Years here.  

All that having been said! Lets look at one last thing.

The original warranty card that came with the FT-75

The date shows 47. 3. 15 

 I believe this is the date of manufacture, and not the actual date of sale.

Again the 47 year of Showa (1972) the third month March and the 15th day.

The original ~ 35 year old boxes!

There's a good reason for that warranty only being valid in Japan,

when you consider the FP-75 with its 100 VAC transformer as noted above.

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