Monday, July 29, 2013 — It’s lunchtime here in Kentucky and I just finished a phone call to Yaesu in bright and sunny California. The problem that prompted my call? My Yaesu DMU 2000.
Hi, my name is Jim, and I’m a bandscope addict.
And as most addicts discover, you never know the full depths of the addiction until you quit — cold turkey. In my case, quitting wasn’t a decision I made … the DMU made it for me.
The DMU actually did not just up and die — but its bandscope function became useless, thanks to the design of Yaesu’s scope board (the part that installs in the Yaesu FT-2000) that places a DC voltage on the output of the bandscope crystal filter. Apparently, this design flaw accelerates the filter’s deterioration; what you wind up seeing one day (as I did a couple of months ago) is the photo at right — a “noise floor” that goes halfway up the walls on the bandscope. Only the loudest of signals pop through the top range of the noise, and there’s damn few of those that I can see. All of the other functions, from the audio scope to logbook and more, apparently work as designed. The only function that was useless was my precious bandscope.
I should blame Icom for my addiction, beginning with the Icom IC-746PRO (a minimally useful bandscope), I moved on to the IC-756PROIII, which had a beautiful bandscope that I fell in love with. I have both rigs still, boxed up with care and in storage. I continue to threaten my FT-2000 with replacement if it doesn’t straighten up and fly right, hi.
The DMU 2000 was part of the package deal I got when I bought the FT-2000, along with matching speaker. The bandscope was a bit of a disappointment because of the display’s speed — it just seems to lag real-time. I love the larger size and the other features, particularly access to the menu settings. There are aftermarket devices that can improve the bandscope function, but I have learned to make do with the factory features of the DMU 2000.
At least until a couple of months ago.
It took me a while to understand what the heck was going on with the display; at first, the “half a screen of noise” thing would eventually dissipate, though it didn’t look like the resulting wave forms matched anything that was actually happening on the band. I googled “DMU 2000 problems” and ran across several web pages and YouTube videos by hams with the identical problem.
The culprit is a 455 kHz crystal filter in the scope board. Thankfully, the filter is not an surface mount component, and it appears to be simple job to unsolder and replace it. Today I looked up the part number in the service manual and order two — I decided to keep one as a spare since this one only lasted seven or eight years, hi.
The filter was only 71 cents, the smallest order I’ve ever placed by telephone. I’m looking forward to getting the part and getting my bandscope functional again. It is an easy fix to a fairly common problem. I’ll let you know how it goes.
73 es CUL … de KY4Z … dit dit
My mother passed away and in her things I found her father’s telegrapher’s key. He was employed by the Northern Pacific Railroad in Minnesota. It is an Electro-Bug manufactured in Fresno, CA. I began researching this and found your posts related to Electro-bug. I am interested in selling this item but am not sure where to begin. Can you give me some direction? I would appreciate it very much.
Thank you.
Sharyl Pyrdol