#247

We show how to fix it

[@dougn7bfs]

Since it was the low current dc bus fuse, maybe it had something to do with an external device that was interfaced to it. Possibly an amplifier connected to an ALC connection on the radio and some fault between the two or possibly an external mic/headset that uses the mic bias from the radio causing the 5 amp fuse to blow. So many variables between your bench setup and the rig owners setup, anything is possible. Thanks for sharing with us Peter!

[@Bass.Player]

That fuse was what I always called 'hard blown' meaning that is was exposed to a high current short. You can always tell by the amount of material removed from the fuse link itself and in this case it was a lot.

[@hectorpascal]

EXACTLY my thoughts. I won't be at all surprised to see this "repair" come back VERY soon!

[@mikefinn2101]

Glad he makes new videos something to enjoy in the evenings all ways a real pleasure to see peter's amazing repairs.

[@araosjo]

Thank you so much. I connected the external cable for Icom tuner withe the radio turned on (my mistake) and it turned off. Your video was a real solution. I was almost crying, hehe.

[@philb5289]

Thanks for the solution to the dead 7300 of mine. It was caused by a poor solder joint on the ACC DIN plug I made up. It let go while pushing the connector into the DIN socket. That'll be the last time I'll try to solder up a 13 pin DIN. Thanks again for this money saving video. 73

[@tech42long35]

Always a lot of fun to see these radios function and be checked while they operate.. Great video thanks So much!

[@zeproo]

An easy fix but VERY VERY important as historical document for the future generations!!

[@PapasDino]

I've seen it before...sometimes a fuse simply fails as a manufacturing defect. But the OM should try to stress the radio by putting it thru its paces to double check. Easy fixes are the nicest but sometimes the most perplexing! 73 - Dino KLØS

[@kopiteinnz]

Always look forward to your videos, thank you for doing what you do

[@45AMT]

Very nice! This owner got very lucky! Such a nice radio. I have one myself and love it.

[@Aleziss]

It happened to me not to long ago, I accidently shorted the band data wire in the accessory port to ground and the radio turned off just like in this video. The 5 amp fuse blew and to my amazement, the radio came back to life after replacing the fuse but also the band data pin is still working providing different voltage output depending on the band the radio is set in... I was sure that the band data pin would have been blown specialty when you think 5 amps whent throught that pin, none of the minuscule traces blew and none of the transistors that drive that band data pin blew ! I wish those pins would be protected with lower amperage PTC but the design protection worked and did protect that band data pin on the accessory port ! Phew !

[@NikiBretschneider]

You are lucky. You know it. In fact, there are a lot of other signals, that could cause issue like this when shorted to the ground, typically auxiliary power for ATU, modem, whatever and I agree with that they should be protected by PTC or fuse, because if you short the +13.8V auxiliary power on the ACC connector (which is present in almost all Icoms and Kenwoods), it sometimes results in a PCB damage, which is a kind of unfortunate. Much worse is when the +8V line (which is present at microphone connector of almost any ancient Icom) is shorted to ground. This results in damaging 8V stabilizer, that, when short is removed, typically puts the 13.8V into 8V line causing a huge damage to the whole transceiver.

[@Aleziss]

@@NikiBretschneider yeah I know I am lucky that no other damage occured to my 7300 ! I am building a breakout cable so I can use isolated audio input/output and while I was thinkering, I've decided to pull all the other pins too in my breakout box so the 13.8V acc pin, band voltage pin, FSKK pin, squelch pin and lastly the PTT pin that works in both direction in/out. I've also installed a DPDT relay so the PTT pin can control an accessory power trought that relay instead of the actual pin... It is while moving my prototype board around that I made the accidental short, I saw smoke from the wire and the radio went silent almost instantly... that is scary to see... But now I think I will protect all the pins with PTC devices like the 13.8V with 050 PTC and the band voltage probably with a 010 PTC directly on my board... no one else than me will fiddle with that breakout box so I "should" know what the pins can drive but in case something goes wrong, at least I will have some protection... humbling learning !

[@Joe_HamRadioGuy]

That was easy😉 but wonder what made it blow out. 🤔 Well if mine stops working that will be the first thing I check. Thank you for sharing Peter You always have very informative videos which is a great help to this hobby. 73's

[@NikiBretschneider]

I am not familiar with IC-7300, but this is a common issue for most ham radio TRXes. We both know that that fuse was blown for a reason and I am almost sure that the reason lurks outside that poor radio. Just check the accessory connector(s), external ATU connector etc., because they are known to provide 13.8V DC output to power the accesories which is switched by the radio power switch, so that voltage have to be taken behind this 5A fuse. And when that auxiliary power outputs are shorted to ground by some external device or miswired cable, they just blow that fuse, but also sometimes damage the PCB near that shorted connecotr or some RFI supress coil if they is present in series with that power output, so that 13.8V DC power output dissapears from that port. And this is something that have to be fixed, but not only in the radio (if there is some damage), but also in the device or cable, that made that fuse blown. In fact, almost everything inside the radio is behind this 5A fuse, the only thing that gets power before it goes to that fuse is the last stage of RF PA. And there are no other fuses than this one. This is what I remember from my praxis in the past when I was in this bussiness.

[@n1zgan1zga44]

I have a Ic-7300 and I can tell you there are sometimes it will pull 23 amps and you Cycle the Power turn it off and Back on and it will pull 18 amps in the Very same place of the Same Band and the Same Mode at 100% Power the Software or the Sensitive Circuits for my Friend and I was talking and his Ic-7300 Went out and I told him too Pull the Top and Check that Fuse and he wouldn't and he Sent it out and it was that Fuse and they Couldn't Find any Reason why that Fuse blew and they Sent it back and it has been Running Great.

[@philkennedy342]

After watching a few of your videos I decided to swap out the pa board on my 817 after it blew its finals easy fix so thanks mate…

[@michaelcarey]

Excellent video as always Peter.

[@chrisscott1547]

You have a nice test bench setup! You should do a video examining each piece of test gear.

[@charliem.9998]

if no one can fix it... Peter (TRX Lab) can ... best amateur radio repair series on youtube ... hats off ... 73s de DL6RDE / AA1KD, Charlie

[@TheMaddogronh]

Thanks for the video,, but I didn't even get to smell the coffee before it was over !! Thanks for another fine video.

[@dan77ring3]

Love your videos!! Keep it up!

[@TheEmbeddedHobbyist]

The fuse should carry 5A for ever! So would need to check the data sheet for fusing times at different currents. A good look at fuse would give you an idea of how much current was flowing at the time. Heat damage would indicate higher current for a reasonable period before fusing, clean but splatter about inside, very high current and very short duration before fusing. But could be just a badly made fuse in the first place, bit hard ti test the fusing current before selling it 🤔

[@rscelectrical7091]

A nice easy fault for a change Peter. Don't get too excited though buddy, we know that they don't happen very often. You take care my friend, Andy.

[@glaros0]

As shown on the startup frequency, the radio died while it was operating on 10m - curious to know what might have caused the blow of the fuse. Also, the -120dBm on the reception is amazing, 7300 seems a quite sensitive receiver! Many thanks for the great video, 73!

[@lylewatts6370]

Thanks for the video and I am sure that there are a lot of these radios out there. If mine acts up with no power on start up I will look at the fuse.

[@111111111Tiger]

Keep it simple. Love it!

[@n1zgan1zga44]

I have a Friend in New York that his Ic-7300 Died rite in the Middle of Talking too me and he Called and told me his ic-7300 just Died I told him too Put the Top Cover for I seen a Fuse When I Opened up my Ic-7300 When I Opened the Tx I seen this Fuse in my Ic-7300 and I Told him too Check that Fuse and he wouldn't Open his Radio and he Sent it out for Someone too Fix and it was the Fuse and they just Changed the Fuse and Sent it back and it's been Working Fine Ever Since. I have Taken Note Sometimes I Get a High amp Reading of 23 Amps at 100% I Turn it off and Back on and it Go's back too Normal 18-19 Amps I never Blown a Fuse but I Keep a Good Eye on it and I know it's putting out all of 110-115 Watts and I have a AH-4 Icom Tuner and I don't have any SWR over 1.5 and some Bands 1 to 1 SWR so how Much Amps Per a Band shouldn't Change but sometimes it will Pull a Lot of Amps in 100% and you Cycle the power and it Total go's Away so I not sure Bug in the Software maybe Sensitive Circuits Not Sure but I know you have too keep your eye on the Amps and It only happens once in a Blue Moon but if it go's out on you Check this Fuse My Friend Could have Saved a Lot of money if he just Pulled the Top cover and Check this Fuse and I would bet the only of this Radio Won't have any Problems it's just a Fluke blowing that Fuse.

[@danewerkSH]

Peter, klasse Kanal. Weiter so👍

[@bs1consilioetprudentia505]

Almost a pity only the blown fuse. Given the method of searching for the short, which the repairer must follow. Thanks for the video.

One thing I would have tried is to operate the automatic antenna tuner while in transmit. It involves motors (and/or relays), which draws more current. Thanks!

[@billnicholson2470]

Easy fix. I hope there is nothing else. Thanks Peter. De KB7ICI 73

[@conorturton]

It's a damning indictment of the state of the hobby that the owner couldn't diagnose a simple fuse blown. They did t even think to test.

[@jamess1787]

This was along my train of thought. I'm currently in the midst of studying, by no means electronics wizard but a tinkerer none-the-less. The requirement to get certified where I live seems like something as trivial as a fuse should have been an easy fix for even the ones who barely passed their qualifications... Then again, maybe the operator who has this radio is an old timer, and nearing the days where he becomes a silent key 😬 - From the land of VE4

[@johncundiss9098]

Maybe Peter is a friend, lives close by and the owner just didn't want to mess with it. 2 repairs across my bench in the past. One was an Icom hf, said no vfo working. The guy did not know there was a vfo lock button in the lower right corner. a second guy swore his HT did not work when it was the PL tone not turned on. I do agree, fix it yourself. Some just do not wanna bother. One other excuse. It is a reason for the "old ham" to get out of the house for a bit.

[@SeanBZA]

Max transmit power of 100W, and a fuse that is rated for 60W. Likely just blew from long term rag chewing by the operator. Power on when power applied is microcontroller remembering last state before power was disconnected, and resuming in that mode, power settings and such.

[@stevetaylor2955]

I think the 5A fuse just supplies some low power circuitry which includes the "power switch" facility i.e. not the current to the PA section, I guess the power cable is fused at 20A

[@stargazer7644]

The current for the final amplifier does not go through that fuse.

[@624radicalham]

I know someone that blew that fuse by trying to connect a Kenwood linear amplifier to the radio

[@charleswoods2996]

Great video! Glad it was in my suggestion feed based on what I generally watch! I've owned a this radio now for about a year and I have to admit I have not had a problem one with it, (thank whatever's looking down on me with blessings!), although I've heard of other operators, one in particular at which the ATU shut down on him and he had to send it back for repair. KD8EFQ/73

[@w.rustylane5650]

If it's just a blown fuse, replace it; however, something caused the fuse to blow. I am used to seeing barrel fuses in radios, but now blade (car) fuses are being utilized. I just wonder why they're using blade fuses now instead of the barrel fuses.? I almost purchased an ICOM 7300 but we have a 2 meter net on Wed. night here in eastern Tennessee and the Yaesu 991a is the only radio I could find that would do all mode including VHF. At least I know how one looks on the inside. Thanks Peter. 73 W Rusty Lane K9POW in eastern Tennessee

[@CliveDrone]

I have a 7300 that is also dead. The fuse is fine, of course. After an accidental PSU overvoltage, it toasted a IC on the main board instead.. Peter would you be interested in repairing this for me. At my expense of course.

[@TRXLab]

Overvoltage is always a serious issue and can hit many components. A repair can be a rabbit hole without any guaranty but very expensive, so no recommendation...

[@enigmarbs2886]

Hi Peter, Another very interesting repair! Small faulty reason, big messy result... For me it looks in your magnification camera, like the fuse getting to warm for longer time because of the body turning "brown" and it looks also like the blades of the fuse are a little bit oxidated? Is that possible reason of blowing the fuse because of overheating the contacts? Es ist immer wieder schön, Deine Videos anzuschauen. 73 de Stefan DG4RBS

[@robertrainey1728]

That was an easy fix even for me Peter..😀

[@radioholicy]

it was serious repair; )

[@grantfullen9559]

Nice video Peter :)

[@af9p]

I blew this fuse while hooking up MFJ 993 auto-tuner. Not sure exactly how or why. I make sure that both radio and tuner are off when making the connections. Ron AF9P

[@dl7majstefan753]

I think, the fuse blew due to overheating. I had a similar problem, where the fuse had bad contacts (i.e. resistance) in the fuse holder and therefore got warm - that increased this resistance and the heat dissipation increased ... and so on.

[@DK5ONV]

There's always people who wrecking radios and people who repair them. Seems to be Murphys Law... 😂😂😂🙋‍♂

[@bblod4896]

Jacket in the lab? Someone didn't pay the heating bill 🤣.

[@michaeltietzyou]

Lucky Day . . . for the Owner 😀

[@brianmiller6320]

A 5A fuse protecting a 100watt radio? If this carries the full supply current it should be more like 15A. What does the circuit diagram show, it might have been a good idea to measure the current through the fuse.

[@101blog]

Should be more like 25A I'd assume the 5A is just the control and Reciever no control no go etc... I did think the same as you initially

[@bravo.juliet]

There are 25A fuses inline with both the red and black dc supply wires of the radio

[@stanley9h1lo]

Like most radios that fuse is for the logic and control side NOT the PA side. The PA is protected via the inline fuse on the DC cable. The PA collector/emitter or source/drain ALWAYS have DC on them even if radio is OFF

[@kevtheskin69]

Hi there, How did you tap the rx for the sinad sniff. Did you take it from the speaker out? Cheers and thanks for the video 73s Kev Mm0kjg

[@stargazer7644]

Yes, he plugs into the radio's speaker out jack. He has an interface box that has a speaker in it so he can still hear the audio.

[@CamilleCullen-ow6qj]

Great video!! I have a 7300 on order and I would like to learn a bit about how it works. Robert K5TPC

[@jil2net]

Hello! Did you have a chance to repair Icom IC-705? I have some problems with mine and probably it's because of the VHF/UHF Tuned BPF (I have too many and to strong spurious signals). But surprisingly I can't enter the Adjust Mode. Maybe you know how to enter the adjust mode? I did everything according to the Service Manual but was not successful. Unfortunately. Thank you.

[@OctavMandru]

Hey Peter, I am sorry if it is a dumn question but what the supply current should be at 105W? Feels like that 5A fuse is underrated?

[@stargazer7644]

The final amplifier current doesn't go through that 5A fuse. That fuse just protects the other circuits in the radio. There is a 25A fuse in the power cord for the finals.

[@stargazer7644]

@@JorksX Oxidation or poor contact in the fuse holders for automotive blade fuses causing voltage drop is somewhat common. Simply clean the blades or adjust the contacts and the problem will go away. This problem isn't specific to Icom. You'll regret getting rid of the fuses the day a final output transistor shorts.

[@Alberto_Alletto]

💪💪💪

[@super-8]

An Nice one for the next tons of years

[@berndb.5097]

Well, why not just a fuse. Heute eben mal leichte Kost 😉 It was entertaining nonetheless 👍

[@bblod4896]

Strange, at 106 watts output, the radio would draw 7.85 amps IF the radio was 100% efficient. Should I assume the power amplifier uses a separate fuse, that the 5 amp fuse is only for the radio minus the power amplifier? Thanks for the video Peter.

[@dazednconfused31337]

I've read my Xiegu G90 (20W) uses up to 5.5A on transmit. The 7300 manual says max TX is 21A. There is this 5A 'circuitry fuse' but also a 25A fuse in the power cable.

[@stargazer7644]

The PA relies on the much larger fuses in the power cable.

[@DO2VI]

Hello Peter, thanks for the great video. The IC 7300 is a great transiver, I have one too. Unfortunately I used the wrong headset adapter 3 years ago. Since then, the power supply to the microphone jack has been defective. Is this a repair effort that a beginner can carry out himself? vy 73 Rene DO2Vi Hallo Peter, danke für das tolle Video. Der IC 7300 ist ein toller Transiver ich habe auch so einen. Leider habe ich vor 3 Jahren einmal ein falsches Headset Adapter verwendet. Seitdem ist die Spannungsversorgung an der Mikrofonbuche defekt. Ist das ein Reparaturaufwand den ein Anfänger selbst durchführen kann? vy 73 Rene DO2Vi

[@TRXLab]

Hallo Rene, für einen Anfänger der noch nie mit SMD umgegangen ist würde ich es nicht empfehlen. Besser zunächst an alten PCB's trainieren und natürlich das richtige Werkzeug benutzen. VG Peter

[@mabo4848]

Tnx

[@paulwerz5122]

The user had 7300 turned on then powered up his power supply the surge took out the fuse

[@stargazer7644]

What surge?

[@karlgoebeler1500]

I know its late But Merry Xmas and Happy New Year everybody

[@destroy_swarm]

I do not understand English well, but apparently the fuse just blew?

[@bigbone88]

Yes

[@destroy_swarm]

@@bigbone88 thanks

[@stargazer7644]

Likely the owner has an accessory cable he's plugging in that has a short in it that is causing the fuse to blow. All he replaced was the fuse. Вероятно, у владельца есть дополнительный кабель, который он подключает, в котором есть короткое замыкание, из-за которого перегорает предохранитель. Все, что он заменил, это предохранитель.

[@diegolab]

my ic7300 died wit a blown capacitor, ferrite bead... DOES THIS IC HAVE SOMETHING TO DO WITH IT ( Tps6211x)

[@markstump7079]

Was he using a MFJ power supply? RIP!

[@beekeeper8474]

Wish you can help me with my icom 7100 no a.m. and low output. Hate to send it to the factory don't trust what they will say and it will cost $200

[@WolfgangS]

Really?

[@LawpickingLocksmith]

wasted 14 min for a fuse

[@darekw325]

Witam SQ5AZZ

[@radioholicy]

ja również witam:)