Repairing a MFJ-259B Antenna Analyzer

November 29, 2014

I’ve had an MFJ-259B antenna analyzer for a while, and for the most part it’s been pretty good. However, in the last few months I’ve seen it intermittently give me really high SWR as opposed to normal SWR.

Usually, that means there’s a break in a transmission line somewhere, but I kept seeing it on different lines. Curiously, it usually went away when I touched the antenna connector.

I wondered if I was adding capacitance or something to the system, but finally I realized it happened when the feedline cable pulled down on the analyzer. It was just a break between the antenna connector and the analyzer.

I took the analyzer apart, re-soldered the SO-239 and I was back in business.

Here’s what I learned when I took the antenna analyzer apart:

  1. Take the battery cover off first (two screws on the bottom)
  2. Next, unscrew both sides (four screws on each side)
  3. At this point, you’ll have access to the battery compartment. Take out the two top batteries and the two bottom batteries (don’t need to take out the rest).
  4. You’ll see four screws that hold the battery compartment to the analyzer. Actually, that’s a lie – only the two right-side screws hold the battery compartment to the analyzer. The left screws are screwed into Delrin insulators. Don’t unscrew the left screws or the insulators will drop off and you’ll have to look under the table for them. Just unscrew the right screws (top and bottom).
  5. At this point you can move the battery compartment to the side, and get easy access to the SO-239 connector. Don’t lose the lock washers that are under the screws.
  6. I suspect they used lead-free solder to solder the connector, which is more prone to cracking than 60/40. I upped the heat a little and mixed in some 60/40 solder to make it more durable.
  7. At this point you can put the 4 batteries back in and test with a dummy load and a good cable. I did this and verified my problems with mystery SWR were gone.
  8. Put things back together in the reverse order that you took them apart.
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Signal out of range on Soyo Topaz S

November 25, 2014

I recently upgraded my monitor from an old Sharp 12″ to a Soyo Topaz S. Things seemed to be going well with the new monitor until I rebooted my Ubuntu Server (which was on 12.04 LTS). When I did that, I got the message “Signal Out of Range” from the monitor, and I couldn’t see what was being displayed.

According to a number of sources, this was because my monitor was being detected incorrectly and choosing the wrong resolution or colour depth. Lots of articles explained that you can change the mode in the config file /etc/default/grub.

To start with, I booted SysRescCD with the option gfxpayload=640×480. This got me to the point where I could see the file system, do an fsck (I’d gone 327 days without one) and mount my root drive in /mnt.

Naturally, when I did that, I discovered the file /mnt/etc/default/grub didn’t exist. That’s because I had upgraded originally from 8.04 LTS and that had never upgraded my grub to grub2.

But at least now I could ssh into my server again. I updated, then upgraded to 14.04.1 LTS because hey, the server needed it anyway. Immediately after doing that, I saw an error with every command, “no talloc stackframe at ../source3/param/loadparm.c, leaking memory”. The quick fix for that (as described in this ubuntuforums thread) was to run pam-auth-update and remove “SMB password synchronization”. As far as I can tell, that hasn’t changed anything with respect to what passwords are used for my shares.

Then I followed the instructions to upgrade from grub to grub2.

After that, I still couldn’t see my screen when I booted… but I had an /etc/default/grub. So I edited it, uncommented the line:

GRUB_GFXMODE=640x480

and had a booting system again. Yay! Eventually I figured out that I could go up to 1024×768 with no problems.

After that I realized I couldn’t do anything with the grub menu. I booted into the system, but couldn’t choose the OS to load with my USB keyboard.

So the next time I booted, I had to switch “USB Keyboard Support” in my BIOS from “OS” to “BIOS”. That fixed the grub menu problem.