Excellent presentation! Your lab is just outstanding, so much equipment around. Sometimes it's not easy to find service manuals and schematics of products, which then is a big trouble because repair becomes almost impossible.
Hi Peter. Another great repair. I would be temped to permanently mount that holder and just leave the fuse in that spot. Kenwood should have made the fuse more accessible. Shorting mic cords are common, and mounting a fuse in an area that requires a tech is silly. Now if he has a problem in the future, he can just replace the fuse without disassembling the whole radio. Always enjoy your video's. This time, I have the popcorn..... and the lazy chair :^)
+Mr Carlson's Lab Hi Paul, thanks!!! It is the second case of this kind but it sounds logical that shorting the mic cords is a common problem.. Well, I'll leave it to the owner he can deicide but despite that I agree that it is really a silly area to place a fuse... Next it is me to have the popcorn and the lazy chair :-) looking forward to your next vid !! Take care my friend!
@@steveluenz3058 connector, cable, mic all check out? If so, you'd have to look in the schematic, and just start following the connections up stream. I was impressed in this vid- they used the other features of the radio to narrow down where the issue was (i.e., they proved the radio could still transmit)
Nice easy repair Peter! Sometimes you never know what causes a fuse to fail, perhaps just a glitch, but it leaves you with that nagging feeling "I wonder what it was?" I have three TM-V71A's so good to file this info away for a potential fix in the future. Thanks for taking the time to share. 73 - Dino KL0S
+Dino Papas Hi Dino, thanks for feed back. Yes I agree it really leaves you with that nagging feeling, but in this case we were not able to find why the fuse failed. 73's
Hey Peter: Thank you for this video. The repair worked great on my TM-D710A. Your instructions gave me the incentive to dive into the chassis and locate the problem. KennyD N2KJD
Great to see your video Peter. I have repaired a Kenwood TM-733 with CPU faulty because after 10 years of QRT, battery is gone down. I have disassembled all radio to access to the battery :( Thanks , I have the popcorn too when I see your video and Mr Carlson videos :)))) Ahahaha. Compliments. 73s de IW0HEX Pasquale.
Enjoying your videos, and I'm learning from them. Thank you. I'm curious to see how they'd ship that tiny little surface mount fuse to you. The stamp probably weighs more than the component! I'm afraid that if this was my radio, the temporary fuse would be a permanent modification!
It comes in a plastic bag I very often need components of this size so no problem..But the temporary solution works fine as well. Thanks for watching 73
!! HELLO !!....SR. , Thanks for this video i coud repaired my Kenwood v71a with the same problem ....muchas gracias, from Puerto Rico Island in the caribbean today April 7 2022..my call Sign is WP4WR ....73s.. .
excellent analysis and subsequent repair, thanks for sharing, I have the same equipment with intermittent audio, could you please give me some tips for its repair?
Is that a 6 or 8 pin modular mic plug??? I was wondering about how cross band works. Is that the same as duplex??? I know the International Space Station transmits on one frequency and receives on another--Tx on 2 meters and Rx on 70 cm. When I had my Kenwood TS-430S with matching PS-430 power supply, I had to take the power supply apart every time I blew a 12 volt fuse which was mounted on a little board in the power supply, which entailed taking out about 24 screws. I finally went to Radio Shack and got an inline fuse holder and mounted it in the back of the power supply. The fuses were pigtail fuses mounted on the little board. So I ran some 12 gauge wire to the fuse holder from the little board. Now it is easier to replace the 12 volt line fuse. I think that should be done to this radio to facilitate the changing of fuses. I consider that a flaw in design. Cheers & 73 from W Rusty Lane K9POW in eastern Tennessee
Great Video Peter,I've never seen such a small fuse,like a grain of rice,if I was the owner I'd want to keep the normal sized fuse in,so your quick repair would be a permanent one. Paul
+Paul Collins Hi Paul, yeah like a grain of rice. Well finally I think it is better to replace a original part although this fix is working well. Thanks for comment. 73
Before closing the unit I would substitute an ammeter for the fuse and measure the current draw with no buttons pressed followed by the buttons pressed individually (including the PTT). I would also tap the circuit boards with an insulated probe (e.g. screwdriver handle) while doing the preceeding to catch any possible intermittent shorts. I do not trust easy repairs, Usually other parts fail before the fuse!
Hi Peter, perhaps I missed something, but I was taught that when a fuse blows the first order of business is to determine WHY it blew. Please correct me if I'm wrong, but I didn't that you found out why the fuse failed.
My TM-V71 only puts out about 38 watts on high power. 4 watts on low power and 9 watts on medium power. I'm not so concerned about the output on Low & medium as I am the high pwr output. Would you have an idea what that could be. I appreciate so much your video's. My IC-7300 quit transmitting. So I replaced the output finals in IC-7300 by watching your video.
HI, EXCELLENT VIDEO!! This is my problem exactly!! It happened all of a sudden. I do have a question. I know you might not remember since this was a few years ago, but the blue wire coming off the fuse. Does it go to the large "trace", larger solder connection UNDER the 3 smaller solder joints on the board?? If you go to time index 27:21 you will see what I am looking at. I plan to replace it with a light duty inline micro fuse holder designed for a car, which is all rubber and it closes shut. THANK YOU AGAIN!!!!! 73, Mark
I believe layer 4 indicated the pink areas represented the bottom foil layer of a 4 layer PC board. Interestingly, it appears the top board is identical to the one in a tm-d710.
+Robert Calk Jr. Hi Robert, thanks for stopping by. Well, yes you are right that would really be the worst case. But the radio is not used in a car so lets hope that it will not happen....
I have the same problem. Tried to take it apart but couldn’t get the main board to release...? Only way in is top down, all screws removed, SO-239 removed, the board is loose, but stuck on antenna side...?
I have an option to purchase the same radio pretty cheap. It can receive but same no key up. How do I purchase the same fuse to repair it? Great video also, I am enjoying it Big Time.
Great video. Am I right in thinking they designed the fuse in the ground side to prevent the ground trace being burnt if an accessory got accidentally connected to supply+ ? The power and signal lines are protected by diodes and limiting resistors. The 4 layers are referring to the construction of the PCB itself, layer 1 is component side (through hole components), 2 internal layers and finally the foil side (SMD components).
+Simon Parkinson Hi Simon, thanks for feed-back! Well, yes we very often find burned off ground traces, so that is most probably one reason. Of course, silly I am.. they layers are corresponding with the pcb. That is clearly shown in the service manual..
That was a strange place and way to mount a fuse. Most fuses are designed to protect the circuit and be replaced with little technical knowledge. I would leave the fuse the way that you repaired it, so that if there was a problem sometime in the future, the owner could get the radio working again themselves.
Hi Peter that is a bad design isn't it? putting a fuse in a place like that, and so small, if it was me i would leave the one you have fitted in there permantly, wonder why it blew in the first place,,,if it goes again will be lot easier to change,,,,Fred UK.
Nice Repair, I may have noticed something, if u look at the resistor R981 (33Ohm, it is in line with the 8V supply) around 19:19 you can see it on the upper left of the mounting screw beside your finger. As far as I can see this Resistor is maybe compromised, it also looks like it has some quite big burn hole in it. But this also could be some solder/flux residue. And the question is why did the fuse blow and what did supply the current? The 33 Ohms are to high to get enough current for the fuse to blow. But the circumstances could be different. And since u have to take it apart again you might have a look at that resistor the zero ohm resistor is probably fine those are quite durable. Keep the work up!
+TecKonstantin Hi Thanks you for your hint. It relay looks like a burn hole. I'm going to check it when the radio is back for final repair. Well but after all that does not explain why it is blown. First idea was that there is something wrong with the mic, but it is working just fine. Anyway the 2 A must be wrong as well. The power consumption over the mic is max. 17 mA. So may be this fuse should be rated max 200mA or 100mA. Again thanks for comment which is very much appreciated. all the best!
+TRXBench No Problem l also love to repair and your videos are extremely pleasant! jup i guess the fuse must be a lower value 2A sounds a bit high. if u have a dead short you get maybe 240mA and like 2 Watts on the resistor that could explain that. Maybe something got into the plug, as a I remember the power pins are next to each other an the pins are quite bare, but you have quite more experience in that.
Hi, I think in this case it is better to use hot tweezers (plastic elements near) or mask them of kapton tape. Hot air may deform it. Greetings to You, I like your video tutorials, very respect to your knowledge. 0
+ELPRO GSM SERWIS ELEKTRONIKI Hi, thanks for feed back and your kind words. Yes a good hot tweezers would be first choice for this job! Need to look around and buy one...
I would have used two soldering irons to remove that tiny fuse, one iron on each pad. Also, I would leave the big fuse in permanently so if it blows again it is much easier to replace next time
Just a handy tip I would mount the fuse holder by a better way or insulate it as you know these little sets can get quite warm and melt that hot glue it's not really the best stuff mounting inside radios !
Greetings, I am a very new HAM, having just received my ticket last May. I have a tm-242 Kenwood, the microphone is not working on this unit. I found a different type of microphone without the touch pad, and it seems to work OK, however I would really like to get the proper mic working. Do you know if this could be my problem as well? I am thinking that there is a lot of circuitry in the mic on the kepad type I have not opened the one with only 4 keys to see if it is the same. The replacement mic does not have lights behind the few keys on board.
Hi Jerry, if a second mic is working good on your radio is is not the same problem as described in the video. There is definitely something wrong in your mic. 73
Hi. I bought a Motorola CM140 radio. From the software, the output power is selectable between 1-28W. The problem is, that the radio is outputting a maximum of 1 - 1.4W (depends on frequency) on the maximum setting. On the 1W setting, it outputs around 0.8W. The transmitted signal is fine, I can open repeaters, audio is OK. I only have a power meter, so can not do any further testing on modulation and such. The radio has multiple protections on the final amp. (over temperature, it can adjust the bias of prefinal and final stage based on forward/reflected power) Could you please say an opinion of what could be the problem? Is it possible that the final is dead, (or dying) even though it has multiple protections, and still transmits at around 1W just fine? Thank you.
Maybe if you put the microphone when the radio is on maybe this happen. I don't know, it's my hypothesis. I believe It's better put the microphone when the radio is off.
Excellent presentation! Your lab is just outstanding, so much equipment around. Sometimes it's not easy to find service manuals and schematics of products, which then is a big trouble because repair becomes almost impossible.
+Kostas Hi, thanks for stopping by... Yes it's true without a manual it can become a nightmare...
One of my favorite radios that you did fixed. Excellent as always showing how to do it.
Enjoyed the troubleshooting skills and repair Peter. Great work in getting the rig back to the owner!
+The Radio Shop Hi, thanks for comment, key was the quick fix, now we have to finalize it. 73
Hi Peter. Another great repair. I would be temped to permanently mount that holder and just leave the fuse in that spot. Kenwood should have made the fuse more accessible. Shorting mic cords are common, and mounting a fuse in an area that requires a tech is silly. Now if he has a problem in the future, he can just replace the fuse without disassembling the whole radio. Always enjoy your video's. This time, I have the popcorn..... and the lazy chair :^)
+Mr Carlson's Lab Hi Paul, thanks!!! It is the second case of this kind but it sounds logical that shorting the mic cords is a common problem.. Well, I'll leave it to the owner he can deicide but despite that I agree that it is really a silly area to place a fuse... Next it is me to have the popcorn and the lazy chair :-) looking forward to your next vid !! Take care my friend!
I have my V71 apart on the bench and my fuse checks OK? What do I need to check next if you might have an answer? Thanks you very much.
@@steveluenz3058 connector, cable, mic all check out? If so, you'd have to look in the schematic, and just start following the connections up stream. I was impressed in this vid- they used the other features of the radio to narrow down where the issue was (i.e., they proved the radio could still transmit)
Just leave that GIANT fuse in, Your fix job looks real nice, Ron, N8DUK Columbus, Ohio
Great video, AGAIN! Thanks. Wish you were closer!
Very interesting and informative. Another terrific video. We all learn a great deal from theses type videos. Thanks
+Satellite_Guy Thank you very much my friend!! 73's
Nice easy repair Peter! Sometimes you never know what causes a fuse to fail, perhaps just a glitch, but it leaves you with that nagging feeling "I wonder what it was?" I have three TM-V71A's so good to file this info away for a potential fix in the future. Thanks for taking the time to share. 73 - Dino KL0S
+Dino Papas Hi Dino, thanks for feed back. Yes I agree it really leaves you with that nagging feeling, but in this case we were not able to find why the fuse failed. 73's
Hey Peter: Thank you for this video. The repair worked great on my TM-D710A. Your instructions gave me the incentive to dive into the chassis and locate the problem. KennyD N2KJD
Really good job on diagnosing this problem. If that was my radio I would just mod the rig to use that bigger fuse .
+Grant Fullen Hi Grant, thanks for comment! Well finally I think it is better to replace it with the original part... 73's
Great to see your video Peter. I have repaired a Kenwood TM-733 with CPU faulty because after 10 years of QRT, battery is gone down. I have disassembled all radio to access to the battery :( Thanks , I have the popcorn too when I see your video and Mr Carlson videos :)))) Ahahaha. Compliments. 73s de IW0HEX Pasquale.
) +Pasquale IW0HEX LOL hi Pasquale, alswasy great to have the popcorn eh?? :-) Thanks for comment always great to hear from you!! Take care! 73's
Hi Peter, what a pain in the rectum design just to get at a fuse!
Yeah so true
Enjoying your videos, and I'm learning from them. Thank you. I'm curious to see how they'd ship that tiny little surface mount fuse to you. The stamp probably weighs more than the component! I'm afraid that if this was my radio, the temporary fuse would be a permanent modification!
It comes in a plastic bag I very often need components of this size so no problem..But the temporary solution works fine as well. Thanks for watching 73
!! HELLO !!....SR. , Thanks for this video i coud repaired my Kenwood v71a with the same problem ....muchas gracias, from
Puerto Rico Island in the caribbean today April 7 2022..my call Sign is WP4WR ....73s..
.
Back again, the information from Peter worked, my V71a is back on the air.
excellent analysis and subsequent repair, thanks for sharing, I have the same equipment with intermittent audio, could you please give me some tips for its repair?
ha ha at the moment you seem to be getting all the easy ones.....great video again many thanks
+charlieoscar09 Hi, LOL yeah, it looks like but sometimes it is okay :-) Thanks for comment!! 73's
Is that a 6 or 8 pin modular mic plug??? I was wondering about how cross band works. Is that the same as duplex??? I know the International Space Station transmits on one frequency and receives on another--Tx on 2 meters and Rx on 70 cm. When I had my Kenwood TS-430S with matching PS-430 power supply, I had to take the power supply apart every time I blew a 12 volt fuse which was mounted on a little board in the power supply, which entailed taking out about 24 screws. I finally went to Radio Shack and got an inline fuse holder and mounted it in the back of the power supply. The fuses were pigtail fuses mounted on the little board. So I ran some 12 gauge wire to the fuse holder from the little board. Now it is easier to replace the 12 volt line fuse. I think that should be done to this radio to facilitate the changing of fuses. I consider that a flaw in design. Cheers & 73 from W Rusty Lane K9POW in eastern Tennessee
The original fuse is crazy! Leave the big one in. Lynton
that's exactly she said
Great Video Peter,I've never seen such a small fuse,like a grain of rice,if I was the owner I'd want to keep the normal sized fuse in,so your quick repair would be a permanent one.
Paul
+Paul Collins Hi Paul, yeah like a grain of rice. Well finally I think it is better to replace a original part although this fix is working well. Thanks for comment. 73
Before closing the unit I would substitute an ammeter for the fuse and measure the current draw with no buttons pressed followed by the buttons pressed individually (including the PTT). I would also tap the circuit boards with an insulated probe (e.g. screwdriver handle) while doing the preceeding to catch any possible intermittent shorts. I do not trust easy repairs, Usually other parts fail before the fuse!
Hi Peter, perhaps I missed something, but I was taught that when a fuse blows the first order of business is to determine WHY it blew. Please correct me if I'm wrong, but I didn't that you found out why the fuse failed.
good work agaen Peter 73
Thanks for another interesting video Peter. Best wishes.
+rupert handford Hi Rupert, thank you!
My TM-V71 only puts out about 38 watts on high power. 4 watts on low power and 9 watts on medium power. I'm not so concerned about the output on Low & medium as I am the high pwr output. Would you have an idea what that could be. I appreciate so much your video's. My IC-7300 quit transmitting. So I replaced the output finals in IC-7300 by watching your video.
Hellow goodday I have a Tm-V71a no power?but i check dc source it is good,but an input of regulator 7808 & 7805 nothing,you can help me.thanks
HI, EXCELLENT VIDEO!! This is my problem exactly!! It happened all of a sudden. I do have a question. I know you might not remember since this was a few years ago, but the blue wire coming off the fuse. Does it go to the large "trace", larger solder connection UNDER the 3 smaller solder joints on the board?? If you go to time index 27:21 you will see what I am looking at. I plan to replace it with a light duty inline micro fuse holder designed for a car, which is all rubber and it closes shut. THANK YOU AGAIN!!!!! 73, Mark
Thanks for comment! Yeah sorry even with the video sequence at 27:21 I can't remember..73
I believe layer 4 indicated the pink areas represented the bottom foil layer of a 4 layer PC board. Interestingly, it appears the top board is identical to the one in a tm-d710.
I'm not sure but most likely.. 73
The fourth layer is the fourth layer of the printed circuit board not the radio.
Thanks. I hope the fuse holder doesn't come loose and fall onto the PCB.
+Robert Calk Jr. Hi Robert, thanks for stopping by. Well, yes you are right that would really be the worst case. But the radio is not used in a car so lets hope that it will not happen....
I have the same problem. Tried to take it apart but couldn’t get the main board to release...? Only way in is top down, all screws removed, SO-239 removed, the board is loose, but stuck on antenna side...?
A hot tweezer would be the best solution. Heat at the tips.. grip the fuse, and lift when melt occurs.
Did you ever put the SMD fuse back in Peter? I think the way you had it fixed was better than the original.
no
nice
I would seriously use that fuse holder permanently.
Maybe you can drill a small hole in the side of the speaker frame to secure it.
+ᗒ╬ᗕ1112223333111ᗒ╬ᗕ Hi, thanks for your feed-back. Well yes I'll leave to the owner to decide...
I have an option to purchase the same radio pretty cheap. It can receive but same no key up. How do I purchase the same fuse to repair it? Great video also, I am enjoying it Big Time.
Great video.
Am I right in thinking they designed the fuse in the ground side to prevent the ground trace being burnt if an accessory got accidentally connected to supply+ ?
The power and signal lines are protected by diodes and limiting resistors.
The 4 layers are referring to the construction of the PCB itself, layer 1 is component side (through hole components), 2 internal layers and finally the foil side (SMD components).
+Simon Parkinson Hi Simon, thanks for feed-back! Well, yes we very often find burned off ground traces, so that is most probably one reason. Of course, silly I am.. they layers are corresponding with the pcb. That is clearly shown in the service manual..
That was a strange place and way to mount a fuse. Most fuses are designed to protect the circuit and be replaced with little technical knowledge. I would leave the fuse the way that you repaired it, so that if there was a problem sometime in the future, the owner could get the radio working again themselves.
+technos123 Hi, yes very strange and not well deliberated where to place. Well I leave it to the owner what he wants to do.. 73
Hi Peter that is a bad design isn't it? putting a fuse in a place like that, and so small, if it was me i would leave the one you have fitted in there permantly, wonder why it blew in the first place,,,if it goes again will be lot easier to change,,,,Fred UK.
+Tom Smith Hi Fred, yes I fully agree, but I leave it to the owner to decide. Thanks for comment!
Nice Repair, I may have noticed something, if u look at the resistor R981 (33Ohm, it is in line with the 8V supply) around 19:19 you can see it on the upper left of the mounting screw beside your finger. As far as I can see this Resistor is maybe compromised, it also looks like it has some quite big burn hole in it. But this also could be some solder/flux residue. And the question is why did the fuse blow and what did supply the current? The 33 Ohms are to high to get enough current for the fuse to blow. But the circumstances could be different. And since u have to take it apart again you might have a look at that resistor the zero ohm resistor is probably fine those are quite durable. Keep the work up!
+TecKonstantin Hi Thanks you for your hint. It relay looks like a burn hole. I'm going to check it when the radio is back for final repair. Well but after all that does not explain why it is blown. First idea was that there is something wrong with the mic, but it is working just fine. Anyway the 2 A must be wrong as well. The power consumption over the mic is max. 17 mA. So may be this fuse should be rated max 200mA or 100mA. Again thanks for comment which is very much appreciated. all the best!
+TRXBench No Problem l also love to repair and your videos are extremely pleasant! jup i guess the fuse must be a lower value 2A sounds a bit high. if u have a dead short you get maybe 240mA and like 2 Watts on the resistor that could explain that. Maybe something got into the plug, as a I remember the power pins are next to each other an the pins are quite bare, but you have quite more experience in that.
+TecKonstantin Thanks again!!
No Problem!
Hi, I think in this case it is better to use hot tweezers (plastic elements near) or mask them of kapton tape. Hot air may deform it. Greetings to You, I like your video tutorials, very respect to your knowledge.
0
+ELPRO GSM SERWIS ELEKTRONIKI Hi, thanks for feed back and your kind words. Yes a good hot tweezers would be first choice for this job! Need to look around and buy one...
Hello Peter I have the same problem with my TM-V71 how much would it be for this repair? Thank you.
great video
I replaced many fuses in motorola equipment Pico little fuse
+DENNIS N Hi Dennis, thank you. Well yes I should put some of this fuses on stock I believe...
I like the New Temp Fuse better then the factory :)
I have the same radio and this is good to know! Thanks :)
+James Cutler Thanks for watching
I would have used two soldering irons to remove that tiny fuse, one iron on each pad. Also, I would leave the big fuse in permanently so if it blows again it is much easier to replace next time
+Herbert Susmann Hi Herbert, well yes first choice would be a quality hot tweezers for this kind of work. Thanks for feed-back!
Just a handy tip I would mount the fuse holder by a better way or insulate it as you know these little sets can get quite warm and melt that hot glue it's not really the best stuff mounting inside radios !
+Sam W Hi Sam, thanks for hint, but as I said it is a interims solution. 73's
Sir i have a unit like that my problem is i cannot unlock it. Kenwood tm-v71a.
Great job thanks for sharing
+26-PS-001 Hi, thanks for watching and comment! 73
Great video--thanks.
+Mr M2HB Thank you!
I guess it might have meant that the PCB itself was a 4 layer board? No matter, it's still a silly place to put a fuse!
+Alan Cordwell Hi Alan, yeah silly I'm was a little bit confused :^)..but you are right not a good place for a fuse. Thanks for comment!
Nice work! Any reason for not connecting the leads to the fuse directly to the SMD points? Just wondering...
+Yann Kitson Hi Yann, thanks for feed-back. Well if ever possible don't use the tiny pads as they are very sensitive and easily comes off....
Good job.
Thank you 73
Greetings, I am a very new HAM, having just received my ticket last May. I have a tm-242 Kenwood, the microphone is not working on this unit. I found a different type of microphone without the touch pad, and it seems to work OK, however I would really like to get the proper mic working. Do you know if this could be my problem as well? I am thinking that there is a lot of circuitry in the mic on the kepad type I have not opened the one with only 4 keys to see if it is the same. The replacement mic does not have lights behind the few keys on board.
Hi Jerry, if a second mic is working good on your radio is is not the same problem as described in the video. There is definitely something wrong in your mic. 73
Hi.
I bought a Motorola CM140 radio. From the software, the output power is selectable between 1-28W. The problem is, that the radio is outputting a maximum of 1 - 1.4W (depends on frequency) on the maximum setting. On the 1W setting, it outputs around 0.8W.
The transmitted signal is fine, I can open repeaters, audio is OK. I only have a power meter, so can not do any further testing on modulation and such.
The radio has multiple protections on the final amp. (over temperature, it can adjust the bias of prefinal and final stage based on forward/reflected power)
Could you please say an opinion of what could be the problem? Is it possible that the final is dead, (or dying) even though it has multiple protections, and still transmits at around 1W just fine?
Thank you.
+worroSfOretsevraH Well difficult to say from the distance can be different things. sorry can't say..
good deed
why did it blow in the 1st place? not a fan of bodge repairs tbh.
+Rubus Roo Hi Rubus, well conclusions seems to be that shorting mic cords are common....Well I'm also not a fan of bodge repairs. Thanks for comment!
+Rubus Roo That was my question. If it blew once and you don't find out why, surely it will pop again...
Maybe if you put the microphone when the radio is on maybe this happen. I don't know, it's my hypothesis. I believe It's better put the microphone when the radio is off.
+pudiful Hi, yes may be. In my opinion it is anyway no good idea to use RJ45 connector for mic's but it is the cheapest..
I reapring this item
that is great