On Saturday, November 7, 2015 at 8:25:39 PM UTC-6, Jeff Liebermann wrote:
I just repaired an old MFJ-269 antenna analyzer. This time, the 4
diodes around the RF connector were NOT blown. Instead, it was crappy
SMT soldering for the components surrounding the diodes. The solder
joints looked ok before I resoldered them, but were obviously a bad
connection because several resistors just fell off the board when I
touched one end with the soldering iron, indicating the other end was
not properly soldered. With the resistor removed, the PCB pad looked
like it had never been soldered. If you don't have good soldering
tools, a steady hand, and a good microscope, DON'T try this as you'll
probably make a mess, as I did before I realized what was happening.

Because the various parts on the RF board were not originally making
good contact to the PCB pads, the calibration is off. The display
reads about 12% too high for impedance and dead on for reactance. I'm
debating if it's worth calibrating.
http://www.w8ji.com/mfj-259b_calibration.htm

Now working on an MFJ-259A, which looks like the usual blown diode
problem:
http://802.11junk.com/jeffl/MFJ-269-repair/

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snip..

Hi Jeff & the list,
I found your post while looking for potential solutions to the problem I'm having with my MFJ-269. It seems to work fine below UHF. Activating the UHF portion, I see "Increase Frequency" in the display, which is usually followed by "Voltage Low .2Volts". I wonder if you've seen this problem before and if you might share any insight as to the usual cause of it.

Thank you,
Robin K4IDC