Sunday, Jan. 12, 2014 — Nearly 7 months ago I began having problems with the bandscope display from my Yaesu FT-2000/DMU-2000/SP-2000 HF station. The problem is (unfortunately) a common one for the Yaesu DMU board that goes inside the FT-2000 — a 455 kHz crystal filter, CF-7001. The filter goes bad and the bandscope shows a steady (and high) amplitude of noise on the display. All of the other functions work correctly — other than the bandscope.
I immediately ordered the filter (it was very inexpensive, so I ordered two), and it has been here on my office desk for most of those same seven months. While removing the old filter and installing the new one isn’t rocket science, the problem I have is finding a large enough table space on which to carefully work on the rig.
The kitchen table was void of the usual clutter today, and I had time to tackle the job. After I removed all the attached cables, I moved the big honkin’ rig to the kitchen. Nine screws secure the cover (3 on each of three sides). The cover raises up at the back and then slides back to disengage the front panel. Easy peasy, right?
The whole thing should have been easy peasy … but was not for several reasons that popped up as I worked.
TINY PARTS, BIG TOOLS, FAT FINGERS. The crystal filter is small; the pins are also very thin and very small. I was tasked with desoldering five pins, another easy task, right? For someone its is, but not me.
First problem was my vision — my reading glasses couldn’t give me sharp enough focus on such a small part; I needed a magnifying glass. I have one, of course, and it was …. well hell, where did I put it?? When did I use it last?? Damn! I’ve only torn through my desk twice since I used it last … whatever organization system existed on my desk (I use the tried-and-true “stack” method) had been obliterated. Grrr!
Of course, the filter is soldered using the lead-free stuff that takes a hotter small iron to flow than my leaded solder. I have a variable heat pencil iron that goes to 50w, but even that really doesn’t flow it really well … and hence my problem. I had to keep my 50w pencil in place on top of the solder wick and wait … and wait … and wait for the solder to flow. Of the filter’s five pens, three unsoldered cleanly; the fourth took a lot of time, the fifth one was a bitch. There are only three electrical connects; two of the pins are simply to hold the filter down. In the process of trying to unsolder the last pin, I crushed the original filter and it fell into pieces. I applied so much heat to the last pad that the solder pad lifted and stuck to my iron.
Had the stream of profanity coursing from my being flowing into the upper atmospher and converted into electrons, I believe Central Kentucky would have been the scene of the most intensely colorful aurora borealis the U.S. has ever witnessed. It is enough to say that I was very, very, VERY unhappy that my ham-fisted desoldering led to a lifted solder pad. And thanks to my lack of a magnifying glass, I really could not tell if it was a vital connection or not. Double Grrr!
With my main HF rig in pieces, I had no recourse but to cuss some more and replace the filter … AFTER I cleared two of the holes of solder, which can be quite a job when you iron offers insufficient heat to do the job. Holes cleared, I inserted the new filter.
In the commotion I found my magnifying glass and gave the board the once-over. It appears the missing pad was not an electrical connection. These appear to be plated-through-the-hole connections, so I figured I would solder the pin where the pad was missing in the hope if a connection is needed, the solder might connect with the thru-the-hole plating. (Yeah, it was a Hail Mary.)
Soldering the teeny pins was easier with the magnifying glass. My rosin core lead solder flowed well with the lower heat. I quickly soldered the five pins and set about reinstalling the board. I put the cover on and then put the rig back into the operating position as I reconnected all the cables.
MOMENT OF TRUTH. It was now or never. If the missing pad was important, I would find out soon enough. I was prepared to remove the board if it was inoperable or malfunctioning and send it out for repair. I applied power to the rig; the DMU booted and the bandscope — correctly — popped up on the screen. Woot!
The rig seems complete now that the DMU bandscope function works correctly. Frankly, I have always wished it was a faster display, but I’m used to it. And when I’m operating, I depend on the display. I use it a lot more than I thought I did — not having it showed me that. Should I upgrade rigs, one of the things I’m going to want is to have a rig that can use an outboard monitor for such a display. I loved the on my FT756PROIII, but I wish it was larger. Still a very good rig, BTW.
Enough for this segment … 73 es GN de KY4Z … dit dit!