Sunday, January 26, 2020

Oh no?

Oh no....what happened here. I was transmitting and suddenly the radio was off! The screen was black and whatever I did it didn't switch back on....

The first thing you think of is.....the power supply. So I took my multimeter and measured 13,8V on the PS terminals. No failure. Then I measured the terminals from the distributionblock, yes....no voltage.

Could be 2 things. The fuse or the electronic over/under voltage device. So I started at the fuse. Measured the fuse with a ohm meter, no problems at all, strange....put it back into the fuse holder and the radio switched back on!

Problem solved you would think....

No, as soon as I started to transmit the radio switched off again! A strange malfunction...

So, in my life as electrician I once heard about old worn fuses. Technically a fuse will hold forever, but in reality when the current through the fuse is almost as high as it can hold the fuse will get warm and will suffer from constant expansion and crimping mechanically till it gets worn and breaks.
The fuse I use for the terminal distributionblock was 20A, close to the 18A a IC-7300 is using when transmitting. So I fiddled a little with the fuse and the radio went off and on....a clear case!


I wanted to know why I couldn't see any breaks in the fuse. Left the 20A fuse, you can't see anything and using a ohm meter it measures fine. At the right the same fuse touched by a small screwdriver, you clearly see the problem now...

The problem however was that I had no spare fuse! Stupid me...it was to late to get to any shop and they are closed at sunday. Luckely an old colleague phoned asking if I could tune two CB antennas for garbage run cars. He had a spare fuse, just the one I need. So he and his mate were more then welcome. I tuned their antennas with the MFJ259 analyser and got the fuse(s) for free, everyone happy ;-)

These guys are really crazy actually. Using a old BMW 7 series to drive from the Netherlands through Denmark, Sweden and Norway just for fun in the middle of the winter. They have no idea what temperature it is in northern Norway I think at this time of the year.....besides that these are old cars using lots of fuel. A complete different adventure compared to our boring radiohobby...

Anyway I have a good quality 25A fuse now. It has a better designed calibration wire inside that can hold the stress much longer. I think my old 20A fuse was some chinese cheap quality after all...

10 comments:

  1. "A complete different adventure compared to our boring radiohobby..." Our hobby is as exciting as you want to make it!

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  2. Vandaag dus meteen maar een paar reserve kopen. Meestal gaan ze dan niet meer kapot. (Murphy)😁

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  3. Interesting! That would have had me puzzled. Good to know that fuses can appear to be in order even though they have actually failed. And as for those crazy guys with the BMW, I once drove from the UK to Monaco in a £200 Volvo DRESSED AS A NUN for charity LOL.

    M7MCQ

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    1. Just as crazy I see ;-)....well if they have fun. I heard about malfunction of fuses long ago but it never happened to me before till last saturday. Somthing to remember...73, Bas

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  4. Useful little story, Bas!

    Driving in Norway is terrible. If you stick to the speed limits, it will take you what seems like 2 years to drive from Oslo to Tromso. But the trees may make you mad before you get there...

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    1. It was the reason I could not be in the AM QSO party last saturday...73, Bas

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  5. Interesting discovery o had a similar experience in my mobile FT-857 with a fuse that was in use over 10 year's deteriorated and caused the radio issues in tx. Eventually I changed both fuses and no problem since. Strange but also good when you fix it yourself best 73. Well done! M0YKS Simon

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    1. There are a few product differences in automotive fuses. I didn't know that till now. I use better fuses now. Always try to fix things myself, that's also part of our hobby. 73, Bas

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Thanks for your comment. Bedankt voor je reactie. 73, Bas