Tuesday, September 15, 2015

FT-1000 MP Mark V Field: Mods for IMD and Key Clicks

There is a long tradition in ham radio of making modifications to commercial equipment to add features or improve performance. It is often viewed as worth the risk of (potentially) lowering resale value if those mods mar the equipment or deter buyers that want a "pure" unit, for the increased utility or mere pleasure of it. Since there are few of us who can design or build a modern transceiver from scratch, it also can be an opportunity to place our personal stamp on  the equipment, if only to show we can do it.

Unfortunately it is also true in too many cases that equipment is sold with fundamental design flaws. There is no incentive for the manufacturer to act when the market doesn't react. That is, if sales proceed according to plan and customers are not complaining, why take on the expense of recalls and factory mods? The truth is that few hams will notice or care.

In the case of the FT-1000 MP Mark V Field I purchased last winter there are two particularly nasty problems: key clicks and excess IMD (inter-modulation distortion). Yaesu did eventually fix the key clicks issue in late models (about 8 years after the rig was brought to market) and never did deal with the IMD problem. It isn't as if Yaesu didn't know about the problems. They appear to have chosen to ignore them.

Lucky for us that there are so bright lights within the ham community who care about these issues, and have the technical ability to find and solve these problems. Those of us eager to transmit clean signals and have receivers up to the demands of the toughest QRM during contests and DXpeditions are thankful these people exist. In this case we can thank Tom Rauch, W8JI. His intensive effort to solve the problems of this otherwise excellent rig are appreciated by many.

Many however neither know nor care. If you don't believe me just listen on the bands. When someone in a CW QSO reports they are using an FT-1000 MP all you need do is tune to either side of their signal. Every time I've done this there were key clicks. For the stronger signals these extended several kHz from their centre frequency. This is not good.

Dime versus 220 Ω SMD resistor from the IF board
Danger lies ahead

Assuming you are like me, and you want to benefit from the solutions W8JI and others provide us, it is not always clear sailing. Sometimes the difficulty of successfully executing the mods is understated. Modern electronics is full of tiny SMD (surface mount devices), masses of cable harnesses and connectors and tightly fit boards and enclosures that make access and interconnection quite challenging.

Some of the challenges with which I am most familiar include:
  • Eyesight: My vision is no longer perfect as it was in my youth. This is true for many of us. Component miniaturization makes it difficult to see well enough to avoid disastrous results. My case isn't helped by the out-of-date eyeglass prescription I am currently using. A hand held magnifying glass helps or, better, a magnifying plate with its own stand to keep both hands free.
  • Soldering: Temperature control and tip selection on our irons is important to proper removal and attachment of circuit board components. The risks are solder bridges, lifted traces and even damaged solid state devices. With an ordinary iron you'll need to be especially careful to avoid damage.
  • Wiring harnesses: Tightly bundled wiring harness and the connectors they plug into must often be moved or disconnected for the required access. Labelling or a pre-disassembly photograph are helpful during reassembly.
  • Fitting: Modified boards must withstand re-installation without component leads touching chassis metal or other exposed components, and not pinching or disturbing fragile wiring harnesses and connectors.
  • Lost hardware: We all drop screws and retention clips, and even SMD components. They're small and our hands are big. Use magnetic tool tips and angle the equipment so that dropped hardware doesn't slide to where it cannot be readily retrieved and can cause damage when power is turned on.
The following is my story of making the W8JI key clicks and IMD mods for the FT-1000 MP. Things did go wrong. I will at least tell you now that in the end I was successful. Perhaps you can learn something from my experience. You should refer to the W8JI article for the reasons and details about the mods.

Interestingly I started this mod in late July. I put it aside until late August when conditions were rotten and I had a few spare hours, finally completing it a few days before publishing this article. For 6 weeks the rig sat uncovered in the shack with wires poking out the side. When the mood would strike me I'd move it to the workbench and continue. This approach may seem odd, but then I don't operate much during the summer so there was no need to rush.

RF board connection for the key clicks mod

This is the most difficult step of the mod because of the difficulty accessing the underside of the RF board. The board is under the fan and power amplifier, and it is encumbered with almost solid, thick wire harnesses with connectors galore. Many of these must be removed before the board can be flipped over.

What I soon determined was that I had two distinct strategies to flip the RF board. But before I describe them, I want to draw your attention to the above photograph of the area (taken after the mod was complete). Compare it to the picture on W8JI's mod page. There is an important difference.

My variant of the FT-1000 MP is the Mark V Field. It does away with the external high-voltage DC power supply, replacing it with an internal AC supply (or operation from an external 13.8 VDC supply) and a power reduction to 100 watts. The metal enclosure to the right of the RF board is the power supply. Other versions of the rig don't have this internal power supply.

The AC supply boxes in the RF board. The board must be slid toward the supply so that the connectors protruding out the rear of the chassis don't impede lifting of the board. With these constraints there is little room to manoeuver the board, requiring more wire harnesses to be moved out of the way. So now we come to my options:
  1. Disconnect a large number of the connectors so that the wire harnesses can be pushed out of the way.
  2. Disconnect a smaller number of connectors but sever several of the plastic cable ties that bundle up multiple wires.
The first option requires taking copious notes and photos, and great care to avoid damaging wires and connectors. The second option is quicker and less complex but requires care in the re-bundling of the wires to avoid stressing wire terminations and to properly route and seat the bundles. The latter item is necessary or the fan unit will not seat properly or risks catching a wire with the fan blades, all due to the tight packing imposed by the power supply. (Of note, the fan in the Mark V Field has a higher duty cycle, even when only receiving, due to the heat produced by the power supply.)

I chose the second option, though I can't say whether that was truly the best. Be thankful if you do not have the Field version when you undertake this mod. The soldering, routing and testing of the one wire for the mod was comparatively trivial.

Soldering the wire to the underside of the RF board was the simplest step in this part of the mod. The adjacent blurry photo shows the care required to avoid solder bridges. The photo is actually of the IF board wire, but the idea is the same.

IMD mod on the IF board

This is perhaps the easier of the two mods. All one has to do is: turn over the IF board, remove an SMD resistor and solder in a new resistor. While the board is exposed a wire for the key clicks mod must be attached, which will be used later.

The IF board is easy to get to. It's on the bottom of the chassis and only requires the removal of 6 screws and unplugging a few multi-pin ribbon cables. Everything else can be easily moved out of the way as the board is lifted and turned to expose the bottom side. I used needle nose pliers to safely lift the screws, with the Phillips screwdriver still holding down the screw to keep it from slipping away. Some care is needed to unplug the ribbon cables so that they are not kinked or subsequently tangled when the board is lifted.

So much for the easy part. The 220 Ω resistor (R2046) should be removed with solder wick or similar device since there is no easy way to lift the SMD component from the board when the solder on one side is heated. I couldn't find my roll of solder wick (it's hiding somewhere!) so I moved the iron quickly between sides of the resistor until it slid off the board. As we'll see, this may have been a poor choice of technique.

My first attempt to solder in the new 220 Ω resistor did not go well. I got too much solder on the lead to the old SMD tab which was then difficult to remove. Holding the lead down onto the tab while I soldered overheated the tab and it lifted from the board. You can see the ugly result above. The other end solders onto the junction between R2049 and Q2016. The resistor end of the foil trace is the safest place to make the connection since it is easier to access and there is no risk of overheating the transistor. Again, I made a mess.

When I was done I slid a short length of tape under the resistor to prevent the leads from accidentally touching any other exposed conductors. I then remounted the board, applied power and confirmed that the radio still worked. However all was not well. When moved back into the shack I discovered that while it received fine the noise blanker didn't work.

The next day I took it all apart again and checked my work. The resistor lead to the old resistor pad had separated. After checking with an ohmmeter that there were no other obvious problems I resoldered the resistor to the pad and made sure it was secure and had continuity. This time when I tested the rig the noise blanker worked.

Key clicks mod on the IF board

With the IF board back in place it was relatively straight-forward to add the circuitry for the key clicks mod. The only important decision is how to mount the circuit, so that is stable and at no risk of contacting the chassis or other components. Happily there is enough room to entertain options.

I chose to use a spade lug as the principle support. The lug also serves as the ground connection, by being secured to one of the screws holding the IF board to the chassis. Bits of black electrical tape prevent unwanted contact between components, wires, circuit board and chassis. W8JI suggests using a small terminal strip, which I could not quickly locate in my junk box. On his web page he shows another way, with the whole assembly freely floating and encased in heat shrink tubing.

The schematic on W8JI's web page does not label the components, and shows variable resistors which allow tuning the circuit for best key clicks suppression (adjustment of waveform ramps). For my own use I hand drew a labelled schematic.

As simple as this mod is, I still managed to make a wiring error. I discovered the error while testing the mod. Using a second receiver I confirmed that key clicks were reduced, but there was some key-down hash and key-up residual carrier energy. Checking my work I discovered I'd connected the IF board wire (top of schematic) to R2 instead of R1.

After correcting the error I was pleased to see that the mod worked as expected. I then replaced the lower half of the chassis. The top was left uncovered until I decided whether to retie the cable harnesses passing between the fan and the RF board.


I don't yet know if the IMD is improved since that will require a more comprehensive test. I do know from recent contests and DXpeditions that I could elicit audible IMD products within a few kHz of exceptionally strong stations and, one time, in a pile up of American stations calling K1N on Navassa Island.

The receiver testing by Sherwood Engineering shows this rig not measuring up to the best with regard to IMD. However I don't know if this is with W8JI's mod. He claims narrow spacing IMD improvement by at least 10 db, and perhaps as high as 20 db. If true that would put this receiver closer to the best. That isn't bad for a 20 year old rig that can be economically purchased on the used market.

Key clicks are far easier to test. No special equipment is desired unless want a precise measurement. Before the mod it was easy to hear key clicks on a second receiver. Use an attenuator and dummy load to ensure that the receiver is not overloaded. I ran full power from the FT-1000 MP into a dummy load -- transmitting a series of dits -- and had no antenna attached to the KX3, on which I listened. The signal strength was over S9 but well within the receiver's dynamic range.

After the mod the audible key clicks almost entirely vanished. As W8JI says, this is not a perfect cure so there will be some residual clicks that a careful measurement will discover. It is however perfectly adequate. I no longer need to feel uncomfortable about using this rig in a CW contest. Don't hook up an unmodified FT-1000 MP to an amplifier or a big antenna until you do this mod! I guarantee that if you don't you will be noticed. Be considerate of others, and protect your reputation.

The one that got away

While I was busy modifying the rig I had the idea of adding something new, for computer-assisted contesting. Quite a few contest and other rig control software support computer keying via a serial COM port. In particular, the RTS and DTR pins of an RS-232 interface. Since these pins are unused on the FT-1000 MP CAT (computer aided transceiver) serial interface I wanted to add the switching circuits for PTT and CW keying onto the same interface.

This turned out to be more difficult than I expected. The DB9 connector on the rear of the chassis, along with the sockets for PTT and CW key, are mounted on circuit boards. That is, they are not chassis-mounted sockets. Adding the circuitry therefore requires lifting and flipping the associated boards to access the points where wires need to be soldered. This would not be easy considering the host of interconnecting cables that would have to be disconnected to accomplish the task. The added wires should also, ideally, have connectors themselves to allow the boards to be more easily removed in future.

I reluctantly decided not to bother. The mod would in any case be of questionable use when operating multiple radios, such as for SO2R contesting. The better and more forward looking approach would be an external keyer such as the USB WinKeyer which is supported by most software and is emulated by some other commercial keyers.

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