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TOPIC: The Deaf Yaesu VX-series

The Deaf Yaesu VX-series 1 year 11 months ago #434

The Deaf Yaesu VX-series -
This all started last year at the Pakistan Jhal Magsi Desert Rally 2014 when my VX-R7 went deaf on both main and sub bands. Got back home and started research which lead me to the problem identification that there seems to be a failure mode in some Yaesu VX-6R, VX-7R -- and maybe the VX-5R handheld radios -- where they lose almost all sensitivity in receive. This problem is caused by failure of the 450kHz ceramic filter LTM450FW.

If you're not comfortable with working on parts this size don't proceed as you will encounter smd components very close to the filter solder points. A good soldering iron with a VERY GOOD de-solder pump is required.
I searched high and low for the filters but could not find them in the local market here in Pakistan. Thus turned to web and found them on alibaba. The irony was that I needed only 02 but the shipper sells 20pcs a lot... so I got them ordered by a friend of mine and today they came all 20 of them :D

There are six screws that attach the back of the radio to the front. Remove the battery pack, remove the screws, set aside.Exercise caution while separating the radio halves. There is a gasket that makes the radio water-tight. It will take a little bit of effort to separate. There is a flex cable attaching the three circuit boards inside. When the halves separate you don't want to damage this cable.

IMPORTANT: To remove the AF board from the radio you will need to pull the two knobs off the top, remove the flex cable, remove the screws from the four corners of the board, remove the nut from the volume/channel knob and remove the spanner nut from the headphone jack. You do not need to remove the screws on either side of the headphone jack. When the necessary fasteners have been removed the board will lift up and pull out easily.
Desolder the old filters. The filter is a 5-pin device, in/out and three ground. The three ground pins will take a little bit more effort to desolder. A Metcal 700F tip and pump-type solder sucker are my preferred tools. Clean up with additional flux and solder braid.
Solder the new part in place. Clean up any flux residue, inspect for any junk like solder balls or bridges and re-assemble.

The radio, back in action. Hard to tell here, but I'm receiving the local radio station which has an extremely weak signal at my workbench.


Blog Post
courtesy:TIMOTHY J CZERWONKA - WO9U
pages.cs.wisc.edu/~timc/e/vx7r.html
Geoff Williams - VK3ZGW:
date: Fri, Mar 21, 2014 at 1:25 AM
subject: VX7R work around
Fix my VX7R recently and it now works fine.
The pcb does not lend itself to fitting an additional component as there is no room on the board and also the connections to the filter comes from both sides. So I fitted the dc blocking capacitor to the filter itself. I've attached a copy of what I did in case you wanted to add it to your web posting on this problem.
VK3ZGW blocking capacitor notes

For more details on why the filters fail please The Mysterious Case of the Withering Filters

images.jpg


IMG-20150417-00042.jpg


IMG-20150417-00043.jpg


sm_vx7r-open.jpg


sm_vx7r-oldfilt.jpg


sm_vx7r-test.jpg


sm_vx7r-finished.jpg


File Attachment:

File Name: VX7R_IF_filter_fix.pdf
File Size: 53 KB
When All Else Fails !!
Last Edit: 1 year 11 months ago by Simple Ham'er AP2CJ.
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The following user(s) said Thank You: Abdus Samad AP2-02-621

The Deaf Yaesu VX-series 1 year 1 week ago #440

Very useful article for hands-on! Out of many, the reason you receive local radio station, may be 1- the filter was over-heated while soldering 2- impedance mismatch because of faulty component like low value capacitor (ceramic especially) or a resistor 3- also look for shields & open circuit before you place a trap. Ceramic filters are very susceptible of change in their electrical properties due to aging, temperature, mechanical handling, humidity and other environmental changes. Always use ceramic low leakage and temperature controlled soldering iron, quality solder flux with wrist grounding band to safeguard against static damage. Clean the worked area with solvent to remove any flux and solder burs.
Good luck!

Abdul Wasay Farooqi
AP2WF
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