Sunday, November 09, 2008

Fixed my MFJ-269 antenna analyser

MFJ-269.jpgI purchased an MFJ-269 antenna analyser more than a year ago and I've never been happy with it.

When it came home the display jittered all over the place and the needles fluctuated wildly. I sent a movie of this behaviour to Andrews where I purchased it and they gave me the address of their repairer so I could ship it directly to him for warranty repair.

When it came back it was certainly better (he said he'd replaced a faulty chip) but still exhibited some odd behaviour, sometimes on power up the power voltage would display values other than around 12V, often 25V or so, then the display would jitter wildly and the impedance meter would wobble.

The SWR looked pretty right and the frequency display was OK so I have been able to use it although with a lack of confidence.

Over the weekend I plunged in and decided to look for the dry joints I've read about. The board itself looks to be wave soldered and looks fine, but their is a flat cable from the main board located at the top of the device under the battery holder. The connections on this cable looked obviously dodgy - I resoldered it and noticed that one of the connections appeared to bubble as I heated it.

closeUp.jpg


The good news is that it has now been reliable for a series of measurements over a number of days. While I recommend this device for the price and functionality, my experience is that the construction leaves a lot to be desired.

Of course, I'm not sure if the bad soldering was by MFJ or the warranty repair service, when it was brand new I wasn't inclined to pull it apart and possibly void my warranty.

I'm looking forward to tuning up an Off Centre Fed Dipole (OCFD) in the week ahead.

Update

Just had another incident of strange behaviour, when switched on the voltage displayed 25V instead of 12V and then readings were erratic. It certainly seems better than it was but this is still not a trustworthy device for me.

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