Kenwood TM-V71 Filter Issue

The Kenwood TM-V71 is a great dual band mobile set that is at home in the car or the home shack. It’s packed full of great features and has a good power output of 50W on both VHF and UHF. I’ve owned Icom, Yaesu and Kenwood dual banders and I just love the TM-V71 so it’s no surprise that I snapped up an ebay bargain for a faulty one (dated 2009) when I saw it.

This issue with this particular set is well know and is caused by some crystal filters that have been contaminated. Symptoms are low sensitivity on one or both sides of the radio and clicks, pops or crunches when receiving a signal. The fix is simple and just involves removing four crystal filters and replacing them.

Four crystal filters on the left hand side.

It’s an easy job and I was going to do it but, I didn’t have to. Kenwood issued a free repair notice when the fault was identified and Kenwood UK were still honoring the notice for a specific serial number range (serial numbers starting with 903 to 003). Off the radio went.

2 weeks later the TM-V71 came back, all repaired for the cost of the outgoing postage. Keen to see what Kenwood had done, I opened the radio up and put it on the bench side by side my late 2015 model. Interestingly, the 2015 model has a slightly revised PCB that has additional capacitors on the filter inputs where as the repaired 2009 model does not. I was half expecting Kenwood to change the entire PCB in the 2009 model but they only replaced the filters so I guess the caps are just an additional precaution and were deemed unnecessary?

DC Blocking capacitors on the newer TM-V71 filters.

Just as a precaution, I’ve ordered some spare ceramic filters and put them aside incase the problem returns. If it does, I will change the filters and modify the PCB to include some small DC blocking caps just like the newer PCB.

5 Replies to “Kenwood TM-V71 Filter Issue”

  1. What are the part numbers where did you get them, what did the cost.

    73 de Geoff vk3sq

  2. Hi Geoff.

    The part numbers are as follows:

    L72-1035-05 _ TOKO A55E
    L72-1034-05 _ TOKO A50E
    L72-1036-05 _ TOKO A55G
    L72-0999-05 _ TOKO A50G

    I purchased from eBay.

    Hope that helps.

  3. I wonder, did the problem ever come back?
    I’ve always wanted to know whether the issue on a lot of these radios is due to the DC Bias voltage or the TOKO filters specifically.

    I did the filters in my D710 a while back and didn’t bother with any bypass capacitors, but I have considered opening it up and adding them. I have a later serial V71 that has the capacitors installed at the factory.

  4. Hi Dale. I’ve replaced the filters in more of these radios than I can remember and never heard of the problem coming back. My belief is that the issue is caused by a “perfect storm” of initial contamination of the filters due to not being sealed correctly and allowing moisture to enter plus the presence of DC on the signal path. If the filters are sealed and dry then the small amount of DC does not matter but when you add the contamination and moisture, bad things happen! I would guess that the later models had blocking caps added to prevent more returns if there happened to be another batch of poor quality filters in the future.

  5. I have a C111xxxx which has been amazing, and I loved it so much I got another v71a for the mobile to replace my alinco. After about 6 mo, I noticed I stopped hearing stations. Turned off SQL and I could hear stations, then noticed I have no s-meter. The serial number is 0010xxxx so I think it should be part of the repair program. However upon opening it up, it looks like it has the TOKO filters, so maybe it had be taken care of, but the issue came back, or I’m chasing down the wrong rabbit hole…

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