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...