N6QW could not resist dabbling with a Yaesu radio as this is a first for me-- read on about my experiences with one of the early FT radios. Email me at FTdx-100.

In looking at one of the popular auction sites the older Yaesu radios seem to command a price nearly 1/2 of what they cost originally. So that tells you even today the older Yaesu radios are very much in demand. Even with ham radios, market forces are very much at work. There also appears to be a virtual endless supply of parts and assemblies available not to mention a very active reflector on the Yahoo Groups forum. Frequently "Tech Specials" are up for auction for prices that would seem to be more inline what a good working radio should cost. Could there be an opportunity to pick up a "not working for parts only' radio and bring that dude back to life? Read on about the restoration of a FTdx-100 that was acquired as "not working".


News Flash.......I am happy to report than on January 16, 2013 at 1753 UTC, that I had my fisrt QSO with the FTdx-100 on 40M SSB with W7POE, George, located in Burien, WA about 50M from my QTH. The signal report affirmed that the FTdx-100 was working and "putting out the juice". Thanks George.

A second contact on 1/16/2013 was with WA7BFN/M7, Duff who was mobile in Spokane, WA on 40M SSB. That was at 2315 UTC. Duff commented on the nice sounding audio.

The third contact on 40M SSB at 0145 UTC on 1/17/2013 was with VA6POP, Vasile, located in Calgary, Canada. Again a very nice signal report. We are on a roll here.

The fourth contact was with W6FDR, Mel on 20M SSB at 1630 UTC on 1/17/2013. W6FDR provided a really good input on the mic gain setting and was familiar with the 6JM6 final tubes. He cautioned about being careful to limit the "tune -up" time as these tubes while having a tremendous power sensitivity were real marginal on plate dissapation. That is sgae advice for any sweep tube amp!

The first DX contact was on 20M SSB with EA3JE, Lou in Barcelona at 1738 UTC on 1/17/2013. Lou was beaming over the north pole -- my report barfoot was 5X8.

On 75M SSB I worked VA7TV and VE7CUL on 1/18/2013 at 0020 UTC. These stations were just across the border from me at about 100 miles distant.

My FTdx-100 is alive!!!

The above photo is what the Yaesu FTdx-100 is supposed to look like -- factory fresh as it was in the late 1960's. This radio came out several years before the introduction of perhaps the most popular Ham transceiver ever, the venerable FT-101. Shown below is my FTdx-100 that was purchased on eBay for $64 including shipping which was $42. So you can well guess what a $22 transceiver that is about 45 years old would appear up close and personal. I hope you all can see the beauty behind all of the dust, dirt and grime! Maybe I am trying to make myself feel better after spending $64.

My game plan is to document what I did to put this fine example of early work by Yaesu back on the air. Mind you this was a hybrid radio which was mostly transistorized using Germanium transistors; but vacuum tubes were used in the driver and final amplifier. A note here about the finals which are 6JM6's which appear to be available today for around $4 each. Perhaps this may be a substitute, with wiring changes, for some of the finals which are nearly "unobtanium". When I test the transmitter section I will know more about this "Golden" find.

This radio was really advanced for its time. It could be controlled by an external VFO as well as crystal controlled and has three slots to add crystals so other parts of the spectrum could be used --like the WARC bands. As a bonus it had an RFA later called a Clarifier by Yaesu.


This is the FTdx-100 as received!


Next we have photos after a bit of clean up using a product called Super Clean.

I used a small paint brush to clean a area and then using another paint brush flushed with water. The knobs were removed and dunked in a small conatiner of Super Clean. Some work with a tooth pick removed all of the grime.


Caution when working on this radio! There are lethal voltages present in the radio that can kill you. This radio was built in the late 1960's, in Japan, so many of the failsafe features we expect in our current products were not law or practice at that time. In the upper left hand corner on the top chassis is a power transformer and several electrolytic capacitors connected to terminal strips. On one of those terminals is 150 VDC for the screen voltage of the Final amplifier tubes. You would never know that as it is not marked or protected.

Later you will see my caution about powering up the radio. I also want to state that all initial work be done with only +12 VDC connected to the radio and that the normal internal power supply be bypassed. All alignment of the receiver stages as well as the low level transmit stages can be done with +12 VDC. The reason for this is that you will need to probe with a DVM, or Oscilloscope as well tracing circuits -- inadvertently touching +12 VDC is not catastrophic but touching +500 VDC may kill you.


The actual restoration process is one that I have used for several projects including, Drake, Heathkit and Ten Tec.

Step 0. This is the getting prepared part which includes having an adequate workspace, good lighting, proper tools and test equipment. Trying to fix one of these radio requires being able to diagnose what is wrong and that only happens when you have analytical tools at your disposal.

Before undertaking any kind of restoration invest in an Oscilloscope (or have access to one) such as a 60 MHz dual channel, a better than average DVM, a frequency counter and an accurate signal source. The signal source can take the form of many of the DDS kits that are available for around $50. Tools include a temperature controlled grounded soldering iron of at least 25 watts. I also have an LC meter that I bought from AADE --about $100. This has proven invaluable in finding problem components.

While we are at it one of the most useful tools I have in the lab is a roll of aluminum foil. I get the cheapo type as tat works very well. When working on this as well as other old radios there was a sequence to the build so as the builders completed the radio some of the last things to go in were the wiring harnesses. This was done to prevent buring the wires while parts were installed. But the problem is that the very small cap or resistor that needs replacing is sitting right under this multicondcutor cable that will get "torched" or maybe "scortched" is a better words because no matter how careful you are, the soldering iron is attracted to those cables like powdered iron filings are to a magnet. Enter the aluminum foil. When I am working in a tight area such as I just described, I cut up various strips and piece of aluminum foil and wrap it around the wire bundles and/or other components. The aluminum acts as a heat shield and prevents the direct contact with the soldering iron hot parts. A simple tool and it saves your radio.

Step 1. Resist plugging in a power supply and firing it up! That is exactly what you will do is "fry the radio" and that is exactly what firing it up means!

Step 2. Get an instruction manual from the Boat Anchor Manual Archive and one exists for this radio and the later model the FTdx-150. When you download the manual note that the schematics are in pieces. A little work that you learned in Kindergarten about matching shapes, cutting and pasting will produce a full sized schematic about 2 foot by 2.5 feet and that is really good for trouble shooting. I mounted my schematic on a piece of cardboard so I can hang it above the bench and quickly follow the signal/circuit path.

Believe it or not but a company in Australia who was the first to sell the radio in VK land actually cretaed a 3 page "Here is the symptom, this is the problem and this is the fix". The company was called Bail (since out of business) and was run by two ham brothers, both SK . Here is a link to those pages.

Step 3. Do a detailed examination of the radio from top to bottom AND take digital photos of all of the sections and areas. You just might have to go back to find out how something was originally installed and that is when the photos will be worth their weight in gold. Observe any broken wires, leaking capacitors, broken parts, controls that don't move freely etc. Keep a detailed record of these observations as this will serve as a check off list of what needs to be fixed, replaced or further evaluated.

Despite doing this, I missed a broken wire, well it was not so obvious. After going through the power up sequence explained later, I did hear noise in the speaker but no signals. I turned on the crystal calibrator and tuned the dial. I could tell the calibrator was being turned "on" but it was way off frequency and very faint.

I then thought I should check the VFO output. There was none and it did not appear as the VFO was "tuning". So I immediately panicked that the VFO was shot. A light bulb went on and flashed "hey dummy" does the VFO have power. Dah, it did not. I checked the on board regulator and found there was +7.7 volts which meant it was way too high, another problem. But nothing on the VFO. I traced the VFO power source wire to the "Select Switch" which sits in the upper right hand corner. That is when I spotted the wire that came from the regulator was not connected to the switch. I soldered it back and the VFO came alive and I could hear the calibrator signals at the proper locations.

A word about the quality of the Ftdx-100 build, actually two words. It sucks! Yaesu simply tacked soldered the wires to the controls and PCB pads. The red/white wire from the volatge regulator to the VFO was not put through the eyelet on the switch but simply tack soldered to the top of the switch contact. It may have just come off and was not evident. Another problem is that the manual speaks to adjusting various inductors etc as a part of the alignment process. This is a near impossibility as all of the inductors had wax poured into the coil forms once the initial factory alignment was done. This will undoubtedly impact any further alignment. Accessibility is another quality issue. No DFM here (Designed for Maintainability.) While I may know what has to be done, gaining access is not possible. The IF amp transformers are buried in a metal box and have the wax over the adjustment slugs. A later photo shows these items.

Step 4. Did I mention that you should not fire up the radio as yet.

Step 5. Look first at the power connections to the radio. This is where I observed a problem with the FTdx-100 documentation. Originally the FTdx-100 must have been sold with just the AC power supply components installed and an add on kit, which appears was intended for user installation, installed the components for using 12 VDC as the power source. These additional components were nothing more than a DC to AC switching inverter that are switched into the primary of the power transformer when the DC cable is installed. The changeover from AC to DC was done with how the power plug was configured. The additional components installed in this radio looked like it was done by a ham in a very cold garage, with poor lighting and a Radio Shack 100 watt soldering iron. All of these connections will need to be cleaned up as it appears there may be a few cold solder joints. So that has been added to my list of things to fix.

Here is the documentation problem I mentioned. In the manual from BAMA there is a single page which shows the DC to AC inverter install yet the main schematic does not show that --so you absolutely need the single page with the DC to AC inverter install as that shows the pin numbers to the Cinch Jones Power plug. The problem: The pin numbers shown on the diagram are the pin numbers as marked on the bulkhead connector and can be seen from the underside of the radio.

As an example one can bypass the power supplies in the radio and simply connect +12 VDC to what is identified as Pin 1 on the schematic and the ground connection to Pin 7. So far so Good! [Connecting +12VDC to just the receiver section is part of the process which will be explained later.] See below for the magic decoder ring of the power connections.


I have a mating Cinch Jones 12 Pin connector which I plan on using for testing and for power off of 12 VDC once I have completed the restoration. Now when I plug my Cinch Jones connector into the Bulkhead Connector --guess what? Pin 1 on the Bulkhead Connector is actually Pin 3 on the Cinch Jones mating connector which also holds for Pin 7 on the Bulkhead is Pin 9 on the Cinch Jones. Had I wired up my Cinch Jones Connector per the wiring diagram I would have fried the radio!

When I took my Cinch Jones Connector and held it above the Bulkhead connector with the connector pins facing inboard the same number sequence was evident Pin 1 on the Bulkhead was where Pin 1 was on the Cinch Jones. Yaesu did not "mirror" the connections so there would be a proper power cable install. I just wonder how Yaesu kept that straight? So let this be a lesson!!!

Step 6. Now that you have the power wiring sorted out fit up a Jones connector with + 12 VDC to what is marked as Pin 3 on the Cinch Jones Connector (Pin 1 on the Bulkhead Connector) and Ground to Pin 9 on the Cinch Jones (Pin 7 on the Bulkhead Connector). Don't power this up yet! As the second piece you need a variable DC power supply from 0 to 12 VDC at about 500 ma. Oh, don't have one of those -- then get one as it is a critical piece of the restoration process. Don't go out an spend a lot of money -- now is the time to homebrew one. Buy an LM317 1 amp adustable voltage regualtor and look on the Internet for the voltage calculator programs. With about a handful of parts you can build an adjustable supply that simpy connects to your shack 13.8 VDC supply. So Ok you are too busy to look up a circuit, see below. Don't power the radio up as yet!

Once again all alignment of the receiver as well as the low level transmitter stages can be done with 12 VDC and bypassing the internal FTdx-100 power supply. Most likely you will need to make many measurements and troubleshoot problems and with only 12 VDC to worry about it can be done safely! See the diagram below for wiring of the Cinch Jones Plug for the initial testing and alignment.


Step 7. Start by looking at several key locations where you can measure voltages and signals. The additional effort is to take the schematic and do an Easter Egg hunt of just where are the cicruits actually located on the mainboard. For instance the +6 VDC regulator which powers the VFO, the RFA and the heterodyne oscillators is located along the left edge of the radio sort of right behind the front panel. Yaesu never showed a pictorial of "what is where" on the chassis. The area between the two metal boxes is the + 6 VDC regulator and you can see the small pot that adjusts the value to 6 volts. See the photo below.

That said I was not able to make it go to 6 volts and about the best I could get was 7.7 volts. When I was doing the initial transmitter testing the CW note sounded awful --it was like a chorus of birds chirping all at once. In looking at the voltage on the VFO during the keying sequence THERE WAS NO VOLTAGE REGULATION. Two minutes with a soldering iron and I installed a 78L06 TO-92 style regulator and the problem was solved. The install invoved nothing more than connecting the input pin to the 12 volt pad on the mainboard regulator. The center terminal was soldered to ground at a convenient location and the three wires that were formerly connected to the mainboard regulator were unsoldered from the pad and soldered to the output pin of the 78L06. It was done manhattan style and is a solid install. Just think, if Yaesu had three terminal regulators back in 1967? I think the regulator cost all of about 50 cents and has dramatically improved the frequency stability.

That said when testing the power output from the transmitter was all but a few watts --so more effort is required for the transmitter. Most likely the final amplifier tubes were "flat" which proved to be the case. But I am getting ahead of myself and the only reason for digressing is that I would heartily recommend making the + 6 VDC regulator change before powering up the radio as then you will be starting with a known quantity.

Step 8. Repair any obvious broken wires, etc. In my radio some person had removed the dual pot that controlled the RF Gain and the AF Gain. The pots and the knob were included with the radio but all I had was a bunch of loose wires sitting behind the panel. See the sketch below, of how this should be reconnected in the event that you experience this same joy. The loose wires included two shielded cables which I suspicioned where the audio controls, which they were. But there were four wires left. This was an Easter Egg hunt. I was absolutely sure about three of the wires but still have some questions about the 4th. I did make an educated guess about this wire and the RF Gain control seems to work fine --but there is that lingering question.

The Schematic shows a 470 Ohm resistor connected to the high end of the RF Gain pot and this resistor on the other end is connected to several other parts of the circuit including one of the relays (there are 4 in this radio). My theory is that this resistor is grounded on transmit and this essentially cuts off the receiver RF amp so you are not pumping RF into the front end of the receiver.


Step 9. One of the reasons that I have been so adamant about not powering up the radio from the "git go" is to recognize that very likely this jewel has not been powered on in a very long time. As such the electrolytic capacitors need to be "reformed" and you can read about that on the Internet. The reforming process involves very slowly applying DC voltage to the capacitors so that the internal process of reforming can occur. Hitting the radio with full voltage can result in blowing many of the electrolytics --that you don't want to do! After assuring yourself that all broken wires have a home and that you wired the power plug correctly so that you are bypassing the Ftdx-100 internal power supply connect your variable supply to the radio and use your volt meter to initially set the output to less than 2 volts. Apply that to the radio and let it set there for about 15 minutes. Next increment the voltage by 1 volt every 15 minutes or so, meaning it will take a couple of hours to reach 12 volts. I noted that at about 6 VDC I started hearing the typical noise you will hear from a speaker. Earlier I had mentioned that after doing this I still did not hear anything other than noise from the speaker and that is when I found the hiding broken wire. So it is wise to go through a process where a circuit is not working to first check does it have any juice (ie voltage to the circuit).



Step 10. Once you have the receiver working you are now ready to tackle getting the transmitter powered on --notice I didn't say fired up. There are two pieces to this step. The first is to address the high voltage power supply by replacing all of the electrolytic caps in the supply. I have made it easy for you in that the table below identifes the caps and the Mouser P/N replacements. The total cost of replacements for these is less than $30 USD. So if you are questioning spending another $30 --you must ask if you even want to continue with the project. I spent effectively $22 for the radio so it was a tough decision but I also reasoned I could reuse the caps for other tube type restorations. BTW there are several ebay lisitings for two of the caps (the 150 Ufd @ 500 VDC) -- I see where the price being asked is about the same for all of the caps. These two jewels can be had for less than $10 at Mouser. Caveat Emptor! In most cases the values specified are the same as the original as to Capacitance value and in several cases it is more. That is not a bad thing AND the voltages specified give a safety margin --as most service in the USA is higher than 110 Volts --so that is also important as the resulting DC voltages will be higher!

As was done with the reforming of lower voltage electrolytic caps, the same process must be done with the HV caps. For this process I have a 0-120 VAC Variac which enables me to slowly apply AC voltage to the radio upon initial application of AC power to the radio. The Variac I have is enclosed in an aluminum box that has a standard duplex outlet installed in the box. I plugged the FTdx-100 AC power cord into one of the outlets and my DVM, set for AC, into the second. I started at 5 VAC and let that sit for about 15 Minutes and then every 15 minutes incremented the voltage by about 10 VAC. So we are again talking about a several hour process. At about 60 VAC I started hearing hissing in the speaker. At about 85 volts the radio was working in the receive mode. Again simply plugging the radio into 120 VAC after it has been sitting idle for a long time places great stress on the electrolytic caps and they blow!

The second piece is replacement tubes. The 6JM6 tubes are avaialble at Antique Electronic Supply (www.tubesandmore.com). The price is around $4 each for the 6JM6A --get a matched set which adds about another $5. So you can get a new set of matched finals for less than $15 which is also the cost of a single 12BY7 driver tube. So it is another $30 for this piece. But I am still under $100. Undoubtedly this jewel was abandoned and stored in some garage, or other dank, dark place most likely because someone "flattened the finals" ( the olde FTF syndrome).

The next section is to highlight identified problems and the resolution

+ 6 VDC Regulator InOp
Bypassed and used a 78L06 three terminal regulator
So Far
Low Power Output (8 Watts)

Ordered new final and driver tubes (6JM6 and 12BY7). I installed just the final tubes (6JM6, matched set, of Westinghouse tubes from tubes and more, $13.10 including matching). Boom --75 Watts on CW on 40M. The new tubes got the power output up into the normal range. The IC was over 200 Ma which is what it is supposed to be --so another positive sign. Still lots more work.

The input power as specified by Yaesu is 120W PEP so power output greater than 1/2 of that is good (50% efficiency). After some tuning of the various circuits, I see about 80 Watts on 80/40M, about 65 Watts on 20/15M and about 50 Watts on 10 Meters. Yaesu does say that the output will be less on 10 Meters. Still not bad for a $13.10 investment. Initially I did have a problem with power output just on 20 Meters as it was only about 40 Watts. I traced that to a dirty switch contact and once that was cleared up the output hits 65 Watts. In case you are wondering, I have made literally hundreds of DX contacts running this same amount of power or less on several of my homebrew radios. The Ftdx-100 power output is quite adequate for barefoot operation as well as driving that QRO amp.

So Far
RFA in Off Tx not = Rx

There is a difference in transmit and received frequenices with the RFA circuit. In looking further at the RFA the way I suspect it was intended to operate is the following: There is a varactor diode in the VFO circuit that is biased to a certain value which is set for the transmit mode. The bias voltage is sourced through relay RL-301 and in the normally closed mode is connected to the voltage on the receive side. Thus when the RFA is "OFF", the bias voltage in receive should the same as in transmit. There are two small trimmer pots connected with the RFA. VR101 is located lietrally in the lower left hand corner of the FTdx-100 with the radio chassis side up and the front panel toward you. This pot sets the range of RFA. Under normal conditions the RFA will give +/- 5 KHz above and below the transmit frequency. I found that by adjusting VR101 that range could be as much as 50 kHz. So you must be careful when adjusting that pot. Now the manual states that the RFA should be limited to +/- 5 kHz AND at the center position will be the same as the transmit frequency.

My initial assessment was that the FTDx-100 with the RFA "OFF" was actaully transmitting and receiving on two separate frequencies. [Actaully when I was initially running 8 watts on 40 Meters, on the flat finals, and tried to break a QSO to get a report --I was advised that 1) it was off frequency and 2) it sounded like crap! So I took some measurements using on +12VDC applied to the radio. I put my HP frequency counter on the VFO output which typically is in the 8.0 MHz range and I keyed the operate switch. The VFO went down in frequency by about 3 kHz. I then repeated the process only this time (RFA OFF) put my DVM on the port where the RFA voltage enters the VFO box. Sure enough the voltage changed --which it should have been the same. There is another pot VR302 which is only active in transmit and enables one to set the voltage level on transmit and thus the transmit frequency. So I thought this should be easy. Readjust the transmit voltage level so that with the RFA "OFF" it will be the same in receive as transmit. Well the range of adjustment on that trimmer never gets you to where you need to be. You can sort of find where the RFA pot is ON that will get you close to the transmit frequency.

Another observation is that the voltage level on either transmit or recive is not totally exactly repeatable. There is a further clue in the 3 sheet troubleshooting guide from Bail (linked earlier) where it mentions the frequency shift and one cure is to switch the two relays RL-301/302. It sounds to me like this has always been a problem. Later you will see where I cleaned the relays but finally resorted to purchasing two new relays.

So here is my two step cure. The first thing I will do is to hardwire a fixed voltage of 4.0 Volts to the RFA port on the VFO. This will enable me to get the radio aligned and fix some other problems. Thus temporarily the RFA will be defeated. I just may tap into the 6.02 Volts fed to the VFO with a voltage divider --literally no current just volts.

Step 2 is to build a new RFA circuit on a small cicruit board using SMD components including an SMR relay connected to the PTT circuit. It will mount right on top of the VFO enclosure using the 4 mounting holes that fasten the top to the VFO box. The heart will be an LM317 regulator with precsision resistors to set the 4.0 Volts and it will also use the original RFA pot on the panel. I think it would be neat to have a RFA and don't want to lose that functionality.


Heterodyne Oscillator

Can't tune the output to 0.2 Volts --have to retrace the wiring. This was resolved by first identifying which trimmer is which. Yaesu does not provide a convenient road map of parts locations. The switch contacts were cleaned up and that finished the job
So Far
Mic Gain (resolder a cap)
Can't access mic amp circuits -- uninstall some parts to gain access. I did find the one problem capacaitor which was identified in the Bail trouble shooting document and hit it with a soldering iron.
So Farar
Capacitor Replacement

Purchase new caps but most likely will have to remove the back panel. I did replace the caps, in fact all of the additional components for the Bias supply and the Screen Supply for the 6MJ6's. See the earlier photo.

I attempted to replace the HV capacitors and some of the lower voltage caps that are used with the DC to AC inverter. While I do have the caps in hand it will be a major undertaking involving a significant dis-assembly, de-installation and rewiring. The caps involved sit in the middle of the radio right at the back edge of the chassis. Major wiring/cable bundles sit over top of the area where the capacitors are soldered to a sub-assembly circuit board. There is absolutely no way of unsoldering the original capacitors without removing the power connector and associated wiring as well as the accessory plug.

I thought if I could remove the back panel with all of the wiring intact I could simply slide it out of the way. I attempted to do that and that appears to be possible but the lead length in some cases is too short and so while not as dramatic as a complete removal it is nonetheless a daunting task. Since I did reform all of the capacitors and the output appears to be OK --- If it ain't broke don't fix it, is sage advice.

Partly done.
Dirty Relay Contacts

I noticed an intermittent operation on RL301 and RL302. These are plug in relays, P/N AE3422 were in the radio but that is not the number on the parts list. I completely disassembled them and cleaned all of the contacts. That seemed to help but I still notice an occassional problem. New replacement relays are available from Kens' Elecctronic Parts [269-345-4609]--about $18 each. The part number to order is 401013-S. For the $18 you also get a socket and the wire spring hold down clip. They are installed in the radio and work perfectly. It turns out this relay is used in other Yaseu radios as well as Kenwood radios.

The actual TR relay as shown on the schematic is a DPDT. What was installed in my radio, and I believe it to be OEM, was a 4PDT. One set of contacts is arranged to switch the antenna bewteen the receiver (NC) and the transmitter (NO). The second set as shown on the schematic has the NC contact connected to the accessory plug as is the NO contact. There is no continuity from these contacts to ground. I suspicion some "idiot" tried to turn the power on an external linear and burnt up the contact. The third set had two wires connected to them with the center leaf grounded and the other was to a wire sticking out the back panel. These also had no continuity when switching to transmit --the idiot tried that again. The 4th set were untouched and I merely connected the center leaf to ground and the NO contact was connected to an RCA jack I installed in an extra hole in the rear panel. I now able to switch in line (notice I didn't say turn on) an external linear amp, an SB-200. Works perfect and I get about 750 Watts PEP with the amp.

So Far
Semiconductor Devices
I have a stock of NTE160 transistors which are HF Germanium Transistors and these seem to be like "Panty Hose" as they have been used in the RF and 1st Mixer and seem to do a very good job without any circuit changes. Ouch --they are now about $7 each --that is not what I paid several years ago. I have since purchased some Russian HF Germanium Transistors and will test those in the circuit. They are far less expensive and so may be "Pant y Hose #2" as one size may fit all. The SK3006 is another pantyhose candidate.
NTE160 works FB.