Alan, great repair job and excellent video presentation with a tremendous amount of detail and clarity. TM-710 users will find this invaluable when their units go south. Thanks for detailing each step.
Great video, and very nice quality from eight years ago. I have a Kenwood tk-8360 that has gone deaf on wideband, I suspect it's the filters. This gives me the confidence to replace them, just need to find a reliable source for new filters.
Hi Alan, I had this very same problem on my FT857D. I was hearing what sounded like thunderstorm static in the HF band even with no antenna connected. I had all 4 filters replaced and caps installed like you did in your video. Problem fixed. Thanks for the video. Terry, WA0DTH
WOW! Coincidentally I just diagnosed an issue with a friend's Kenwood TM-V71AE to this same component. As I watched your video the main PCB - even the speaker location and mounting - looked identical to the V71. As you demonstrated the problem, you were showing the same issue as in the V71. And when you reached the crystal filter, I had already been there and, once the part arrives, will have done that. What's even more exciting is that you've considered the why: why did the filter fail? So the same mods will be applied to my repair, and we should have a very happy V71 owner. I'll create a small video that demonstrates the V71's issues and fix, once we get there. Thanks for your efforts in producing this material. Good show.
Many thanks, your demonstration gave me the information and confidence I needed to to repair my radio. I find your videos very helpful and informative. Thanks again for taking the time to produce this video. 73 - John.
Another great video. The problem is likely a designed obsolescence. It gives people a reason to love hardware mods. Adding Heat-shrink tubes to this mod would be a prevention measure against shorts to metal case.
Thanks for the video, it was a very clear explanation of how to use this tuner. I just received one and I'm looking forward to trying it with my FT-817ND. 73 de KB3MNK.
Is it possible to isolate the filter input and output pins with from their pads with tiny bushings allowing the capacitor to be mounted to the filter pin and connected back to trace with jumper? This way no trace cuts would be necessary. It would be nice if the pin holes could be enlarged slightly to make a little more space for the bushings.
Out of curiosity, I cracked open my used, but recently purchased Kenwood TM-V71. It appears as though a circuit design change happened at some point. DC bias blocking caps have been added. I know you show the TM-D710 in your video (and I'm talking about a TM-V71), but from what I've seen, they are essentially the same radio minus the built in TNC/APRS stuff in the head unit of the 710.
I think the moisture issues were water intrusion inside the filter cavities during washing in manufacturing. Residual humidity shouldn't be an issue. Plus, the DC has now been removed, so the driving force behind the dendritic growth is gone. So, probably no need for the coating.
This kind of failure needs three things: moisture, contamination, and metal. Conformal coating is really just a dirt barrier or insulation layer. The coating might slow down the moisture absorption but it never eliminates it. Moisture will always make it through if given enough time. The key to fixing this kind of problem is to focus on the contamination and remove it during manufacturing. Use a cleaning process that is well matched to the chemistry of the fluxes involved. Proper cleaning is surprisingly hard to do in the real world. Once you've cleaned it you can coat it to keep future contamination away from the metal. If you coat without perfect cleaning you may buy a little time but once it fails the repair is harder.
Really interesting, I have a TM-V7A dualbander that seems to come off squelch fine but you don't get any intelligent sound out of it, I'll try switching between narrow and wide and see if I have any change
i have a kenwood tm-v71 with a faulty vfo.numbers and leter are crambled.it receive and transmit well but i want to use both vfo at diferents frecuencies.i search and nothings find.
Rather than cutting PCB tracks would it be possible to suck the solder from only the input & output holes on each filter pin and slip insulation sleeving over each I/O filter pin leaving just enough filter pin exposed to solder to (the through holes appear to be quite big) then solder one end of the capacitor to the PCB land and the other end of the capacitor to the exposed part of a filter pin?
Yes, I think so - provided there was enough lead length to elevate the filter and bend the I/O leads out. If I ever have to do this again on another rig, I will try it.
Just curious, why wouldn’t a single series capacitor be enough to prevent DC current into the filters? Why two per filter? Great video as always. I appreciate how you show every step and discuss what you are planning to do. 73!
There is a DC potential on the circuits at either end of the filter. The issue wasn't about keeping DC from appearing *across* the filter, it was about keeping DC with respect to ground off of the input and output terminals of the filter.
The IF frequency is 450-455kHz, so you just have to make sure you have a low reactance at that frequency. Value not very critical. I used 0.1uF. Voltage rating I used was 25V because that's what I had.
I thought about that, but there wasn't too much room to lay them on their sides. Maybe could've done that with SMT devices between the leads and the PCB.
I have a beginners question... wouldn't adding those caps mess the frequency response of the filters (-3dB corner, Q-factor, etc)? or are those active filters?
Good question. In this case, the caps are a high enough value for their reactance to be low enough to appear as a near short circuit at the frequency of interest.
I did this modification and repair. The VFO A is now very deaf and does not report a signal. Tuning both VFOs to the same signal from my SG at -86dbm, VFO B properly opens the sq and reports the signal and demods just fine. The VFO A I have to turn the sq all way down (open at no signal) and I can hear my SG FM tone (using a proper HP testset). I wrongly assumed the left side of the filters was VFO A and I redid it.... and nothing changed, as that was fine. I assume VFO A is CF486/487, correct? What could be wrong?
Kenwood TS-2000 I have can have the same issues with having a DC bias on its filters and was a common failure.. I was reading they fixed it but with a different run of filters.. Also heard some thing about overheating of the filters when they where soldered on the board, that may have comprised the filter witch would let moisture enter them and I guess that make sense. P.S. FIRST!
Dear sir i am having a problem in which radio transcevier stays busy i.e in receiver mode only in all channels though channels are free please give me some hint on repair
Very difficult to diagnose remotely. First thought - receiver "busy" mode is when the squelch is open. Does it still stay in "busy mode" when the squelch is turned up? If so, then look for a fault in the squelch circuit, or something causing a false signal in the receiver.
hi. Why would there be any DC bias anyway? So the filter awaits AC, because signals are like this ("sin"-, "cos"-like) and therefor DC is...bad? Is my conclusion right like this? warm regards
The DC bias is there because of the switching diodes that are used to select which filter is being used. Nothing wing with using switching diodes, but there should have been AC coupling caps between the diodes and the filter input/output.
I'm currently working as a radio service technician and this is really the problem I always encounter with this radio transceiver. I think this is really a design problem. And not only this model is having the problem,also the TM-V71 which is the same with TM-D710 but with different display,and the TM-271. And not only Kenwood suffered from this problem,even some Icom model like IC-2100,IC-2200, ect. And also some Marine radio like the Standard Horizon.
They were ordered by my friend directly from Kenwood's parts supplier, using Kenwood's part numbers from the service manual. The filters are made by Toko I believe.
Yes, Toko. I have cleaned mine once probably 2 years ago, according to Tasos recommendation. I'm ready to make the radio useful again. One reason I asked is because your replacements did not appear to be Toko. Thanks.
Do you have any knowledge of a clicking/tapping noise that occurs on these radios? It is my understanding that it may be related to the hand mic. It is still present on my TM-D710GA but has occurred on older TM-D710 radios as well.
555prodrag I think I read that Kenwood addressed this design flaw in the later revision, but I can't be sure. If you have a servicing dealer, you may want to check with them (or take a look at the schematic of the new rig).
On icom 2820h happen the same problem, and those filters have condenser on input and output, so no voltage goes through them. But still I having the same issue with those ceramic filter. I replace the filters and all ok now.!!
+w2aew The Yaesu filters are about about $1.00 each. Kenwood, Yaesu and Alinco all have the same issues. I was buying 25 filters at a time from Yaesu for a few years but since they started potting the filters I have seen very few (still some even the potted ones) fail. Paul de W4PGM
The DC bias has been proved to be rubbish, the filters fail because they are not sealed and are attacked by moisture in the air which corrodes them internally. It is the same problem I have with my tools rusting in the tool boxes.
So was it just a poor cleaning process or a bad lot of filters that caused the problem - and that properly cleaned/manufactured filters would be OK with a standing DC bias on them?
@@w2aew Well when I looked into this some years ago as I have been carrying out these repairs on Kenwood, Yaesu, Icom and a number of radios fitted with these filters circa of this age I found little to no evidence on the manufacturers errata / datasheets suggesting having dc bias on these will cause damage. I have seen these ceramic filters take up water over several months in the workshop after removal and replacement and certainly the replacements I have been fitting have yet to develop the problem(s) associated with these. Hope this is useful, kind regards Mark.
What is with the hideous SO239 connector. Surely any self respecting amateur would demand a TNC or MPL on V-UHF especially for such a compact radio as this or am I just spoiled from formerly playing with Motorola mobiles. Also looking at some of the suggested videos this issue is not unique to this radio. Similar design decisions/shortcuts have been used in other brands and models. Trick repair well done Alan.
Alan, great repair job and excellent video presentation with a tremendous amount of detail and clarity. TM-710 users will find this invaluable when their units go south. Thanks for detailing each step.
It's was a tedious mod, but worked out well in the end.
Great video, and very nice quality from eight years ago. I have a Kenwood tk-8360 that has gone deaf on wideband, I suspect it's the filters. This gives me the confidence to replace them, just need to find a reliable source for new filters.
Hi Alan, I had this very same problem on my FT857D. I was hearing what sounded like thunderstorm static in the HF band even with no antenna connected. I had all 4 filters replaced and caps installed like you did in your video. Problem fixed. Thanks for the video. Terry, WA0DTH
WOW! Coincidentally I just diagnosed an issue with a friend's Kenwood TM-V71AE to this same component. As I watched your video the main PCB - even the speaker location and mounting - looked identical to the V71. As you demonstrated the problem, you were showing the same issue as in the V71. And when you reached the crystal filter, I had already been there and, once the part arrives, will have done that.
What's even more exciting is that you've considered the why: why did the filter fail? So the same mods will be applied to my repair, and we should have a very happy V71 owner.
I'll create a small video that demonstrates the V71's issues and fix, once we get there.
Thanks for your efforts in producing this material. Good show.
Many thanks, your demonstration gave me the information and confidence I needed to to repair my radio. I find your videos very helpful and informative. Thanks again for taking the time to produce this video. 73 - John.
Great Job Alan! Hey... You forgot to put that regulator tube back in 13:33 :^)
Another great video. The problem is likely a designed obsolescence. It gives people a reason to love hardware mods. Adding Heat-shrink tubes to this mod would be a prevention measure against shorts to metal case.
Excellent video with nice details and modification. Great work done. Regards,
Thanks for the video, it was a very clear explanation of how to use this tuner. I just received one and I'm looking forward to trying it with my FT-817ND. 73 de KB3MNK.
Nice job, not many people are going to do that type of repair.
Is it possible to isolate the filter input and output pins with from their pads with tiny bushings allowing the capacitor to be mounted to the filter pin and connected back to trace with jumper? This way no trace cuts would be necessary. It would be nice if the pin holes could be enlarged slightly to make a little more space for the bushings.
Thank you so much for documenting this detailed fix!!!
Thanks for this informative video, will have to keep this url for when my dual-band kenwood has the issue.
Great video I can't wait to watch more of your videos now.
Thanks!
Nice, as usual Alan.
Nice transceiver too
Out of curiosity, I cracked open my used, but recently purchased Kenwood TM-V71. It appears as though a circuit design change happened at some point. DC bias blocking caps have been added. I know you show the TM-D710 in your video (and I'm talking about a TM-V71), but from what I've seen, they are essentially the same radio minus the built in TNC/APRS stuff in the head unit of the 710.
Great video, I always like to find a tangible reason for component failure too.
Thank you. Saved the video for later...have a 710a and V71a here.
Alan, would you consider a spot of conformal coating (spray) for a repair like this given the moisture issues and as a ways to extend the life?
I think the moisture issues were water intrusion inside the filter cavities during washing in manufacturing. Residual humidity shouldn't be an issue. Plus, the DC has now been removed, so the driving force behind the dendritic growth is gone. So, probably no need for the coating.
This kind of failure needs three things: moisture, contamination, and metal. Conformal coating is really just a dirt barrier or insulation layer. The coating might slow down the moisture absorption but it never eliminates it. Moisture will always make it through if given enough time. The key to fixing this kind of problem is to focus on the contamination and remove it during manufacturing. Use a cleaning process that is well matched to the chemistry of the fluxes involved. Proper cleaning is surprisingly hard to do in the real world. Once you've cleaned it you can coat it to keep future contamination away from the metal. If you coat without perfect cleaning you may buy a little time but once it fails the repair is harder.
Jon Bertrand
It seems to work well on washing machine PCB's.
Really good info here .
Thanks for making these videos.
Really interesting, I have a TM-V7A dualbander that seems to come off squelch fine but you don't get any intelligent sound out of it, I'll try switching between narrow and wide and see if I have any change
i have a kenwood tm-v71 with a faulty vfo.numbers and leter are crambled.it receive and transmit well but i want to use both vfo at diferents frecuencies.i search and nothings find.
You have the hands of a surgeon. 73 AL3A
Excellent video, as usual! Thank you.
I was hoping you would try to crack one of those faulty filters open to see what is wrong with them from inside.
Rather than cutting PCB tracks would it be possible to suck the solder from only the input & output holes on each filter pin and slip insulation sleeving over each I/O filter pin leaving just enough filter pin exposed to solder to (the through holes appear to be quite big) then solder one end of the capacitor to the PCB land and the other end of the capacitor to the exposed part of a filter pin?
Yes, I think so - provided there was enough lead length to elevate the filter and bend the I/O leads out. If I ever have to do this again on another rig, I will try it.
Just curious, why wouldn’t a single series capacitor be enough to prevent DC current into the filters? Why two per filter?
Great video as always. I appreciate how you show every step and discuss what you are planning to do. 73!
There is a DC potential on the circuits at either end of the filter. The issue wasn't about keeping DC from appearing *across* the filter, it was about keeping DC with respect to ground off of the input and output terminals of the filter.
@@w2aew got it! Thanks for explaining. I have a V71 so I assume I may be in for a similar repair. Take care and have a good morning. -E
Absolutely fantastic video. Thanks much!
Very interesting and informative video/lesson...Thank You!
How was the value and voltage rating of the capacitors determined?
The IF frequency is 450-455kHz, so you just have to make sure you have a low reactance at that frequency. Value not very critical. I used 0.1uF. Voltage rating I used was 25V because that's what I had.
***** Thank you for the reply!
Wonder if standing them on their sides and just using 10n ceramic wire ended devices would work as well. Less likely to damage thin traces.
I thought about that, but there wasn't too much room to lay them on their sides. Maybe could've done that with SMT devices between the leads and the PCB.
***** Thought of that, but a bear to solder then. Wonder if there is a filter with same characteristics but which is thinner that can be used.
Excellent video. Thanks for your efforts. Hope I never have to make the repair myself.
Awsome fix and design upgrade! I have had such symptoms and 1 by 1 these filters appeared to die. Any suggestions for sourcing these ?
I ordered them directly from Kenwood.
Great repair.
I have a beginners question... wouldn't adding those caps mess the frequency response of the filters (-3dB corner, Q-factor, etc)? or are those active filters?
Good question. In this case, the caps are a high enough value for their reactance to be low enough to appear as a near short circuit at the frequency of interest.
I did this modification and repair. The VFO A is now very deaf and does not report a signal. Tuning both VFOs to the same signal from my SG at -86dbm, VFO B properly opens the sq and reports the signal and demods just fine. The VFO A I have to turn the sq all way down (open at no signal) and I can hear my SG FM tone (using a proper HP testset). I wrongly assumed the left side of the filters was VFO A and I redid it.... and nothing changed, as that was fine. I assume VFO A is CF486/487, correct? What could be wrong?
I don't recall which set of filters were for which band - and I don't have the radio or documentation available any longer to check.
Kenwood TS-2000 I have can have the same issues with having a DC bias on its filters and was a common failure.. I was reading they fixed it but with a different run of filters..
Also heard some thing about overheating of the filters when they where soldered on the board, that may have comprised the filter witch would let moisture enter them and I guess that make sense.
P.S. FIRST!
How rugged do you feel this radio is for mobile use compared to something like the 2200H?
Dear sir i am having a problem in which radio transcevier stays busy i.e in receiver mode only in all channels though channels are free please give me some hint on repair
Very difficult to diagnose remotely. First thought - receiver "busy" mode is when the squelch is open. Does it still stay in "busy mode" when the squelch is turned up? If so, then look for a fault in the squelch circuit, or something causing a false signal in the receiver.
hi. Why would there be any DC bias anyway? So the filter awaits AC, because signals are like this ("sin"-, "cos"-like) and therefor DC is...bad? Is my conclusion right like this? warm regards
The DC bias is there because of the switching diodes that are used to select which filter is being used. Nothing wing with using switching diodes, but there should have been AC coupling caps between the diodes and the filter input/output.
I'm currently working as a radio service technician and this is really the problem I always encounter with this radio transceiver. I think this is really a design problem. And not only this model is having the problem,also the TM-V71 which is the same with TM-D710 but with different display,and the TM-271. And not only Kenwood suffered from this problem,even some Icom model like IC-2100,IC-2200, ect. And also some Marine radio like the Standard Horizon.
I have a d710 with this problem. Is there any way I could send this to you to repair?
I'm sorry - but I only work on my own radios, or those from family or close personal friends.
@@w2aew Ok thank you
I'm having same problem what does it cost for repair like this
You'd have to check with a repair shop.
@@w2aew thanks
very nice repair I think I will be doing it to my tmv71a ;(
Did you do it Erich. Are they the similar radios?
do you know if the latest versions of this radio have the same issue??
+Mike Sloan I've been told that it has been corrected in later versions, but I have not verified it myself.
Where you buy the ceramic filters tnx 73
I bought them directly from a Kenwood parts supplier - www.pacparts.com
@@w2aew Tnx 73!!
Alan, Can you let us know from where you were able to order the filters? (Brand, part #, etc...)
They were ordered by my friend directly from Kenwood's parts supplier, using Kenwood's part numbers from the service manual. The filters are made by Toko I believe.
Yes, Toko. I have cleaned mine once probably 2 years ago, according to Tasos recommendation. I'm ready to make the radio useful again. One reason I asked is because your replacements did not appear to be Toko. Thanks.
Good repair, well explained.
Does anyone know if Kenwood has corrected this problem in newer units?
I aldso am wondering the same.
Do you have any knowledge of a clicking/tapping noise that occurs on these radios? It is my understanding that it may be related to the hand mic. It is still present on my TM-D710GA but has occurred on older TM-D710 radios as well.
what vacuum desoldering iron is that?
It's a Hakko 808
*****
I love my Hakko 808!! It's worth it's weight in gold! But I'm happy that it doesn't cost that much.
Will this be an issue if I purchase a brand new Kenwood TM-D710GA?
555prodrag I think I read that Kenwood addressed this design flaw in the later revision, but I can't be sure. If you have a servicing dealer, you may want to check with them (or take a look at the schematic of the new rig).
On icom 2820h happen the same problem, and those filters have condenser on input and output, so no voltage goes through them. But still I having the same issue with those ceramic filter. I replace the filters and all ok now.!!
Nice video. Compliments !!!
how much was the actual filter?
I'm not sure - my friend that asked me to repair it had already ordered the replacements himself.
+w2aew The Yaesu filters are about about $1.00 each. Kenwood, Yaesu and Alinco all have the same issues. I was buying 25 filters at a time from Yaesu for a few years but since they started potting the filters I have seen very few (still some even the potted ones) fail. Paul de W4PGM
Great info thanks!
Great video
Many thanks
73
Great video :)
Masterful! Masterful indeed. Do you know where I can send mine for this repair without paying too much? Thank you. Matt / KF4ULD
Unfortunately, I don't. You may want to check with the elmers and homebrewers in your local ham radio clubs.
w2aew okay thank you for the quick reply sir.
Yaesu has the same issue in many of their rigs...
+KF5OBS yep to true
Just great job well don't I will know take my 710 apart and examine n Pathan area please make some more videos
The DC bias has been proved to be rubbish, the filters fail because they are not sealed and are attacked by moisture in the air which corrodes them internally. It is the same problem I have with my tools rusting in the tool boxes.
Nice repair, although the carving up and installation of dc blocking capacitors is unnecessary as the failure mode is hygroscopic related.
So was it just a poor cleaning process or a bad lot of filters that caused the problem - and that properly cleaned/manufactured filters would be OK with a standing DC bias on them?
@@w2aew Well when I looked into this some years ago as I have been carrying out these repairs on Kenwood, Yaesu, Icom and a number of radios fitted with these filters circa of this age I found little to no evidence on the manufacturers errata / datasheets suggesting having dc bias on these will cause damage. I have seen these ceramic filters take up water over several months in the workshop after removal and replacement and certainly the replacements I have been fitting have yet to develop the problem(s) associated with these. Hope this is useful, kind regards Mark.
Man you are awsome..
Great job, rather you than me lol. Thanks for the video.
Great information ...... now I am just hoping mine doesn't develop this issue. Thank you. N7NVK
Forensics, research, re-manufacturing its all here.
What is with the hideous SO239 connector. Surely any self respecting amateur would demand a TNC or MPL on V-UHF especially for such a compact radio as this or am I just spoiled from formerly playing with Motorola mobiles. Also looking at some of the suggested videos this issue is not unique to this radio. Similar design decisions/shortcuts have been used in other brands and models. Trick repair well done Alan.
I believe the version sold in Europe has an N connector.
GREAT Video! Thank You! de W4YJ