Hi Dave, and the group:

I quite understand your frustration, particularly after what you probably think you did to cause the problem seems so dumb in retrospect.

Be rest assured you aren't the first and probably not the last to hook up the power supply leads the wrong way.....being mere humans it's real easy to do. Other things, like your problem are easily caused as well.

In the commercial world of radio's (R/T) the Tait/Motorola/etc rigs have all sorts of "idiot proofing" built in....the most useful ones being FAST blow fuses or circuit breakers combined with a very large (>100 amp) suicide diode in the main power leads to remove power really, really fast in the event of a major problem.

In all my amateur installations I have included a similar system utilising high current diodes removed from old car alternators and an inline fuse rated at only a few amps above the rigs maximum current requirements, all this placed in the main power line to the rig. It saved my '817 from instant suicide when I hooked it up in a mates boat, not realising that it was a 24 volt system. the (5 amp) fuse blew almost instantly and saved the rig. This system also has a thyristor and 15 volt zener to guard against over voltage since I was told that the finals can die real fast with over voltage. It (the '817) is still working ok.

So I would recommend that a similar system should be provided for ANY rig that has an external power source, why yaekencom don't do this as a matter of course is beyond me!

Don ZL1THO

[snip]

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In the commercial world of radio's (R/T) the Tait/Motorola/etc rigs have all sorts of "idiot proofing" built in....the most useful ones being FAST blow fuses or circuit breakers combined with a very large (>100 amp) suicide diode in the main power leads to remove power really, really fast in the event of a major problem.

Just remember, as soon as you make something "idiot-proof", nature will invent a better idiot...

A fuse and sacrificial diode are all very well, BUT.. Fuses take time to rupture, and a power transisistor always has, and always will be the fastest fuse on 3 legs... or 4 or whatever. For higher power items, I prefer the Idiot-Proofing method of a big relay!... Car accessory type of thing, in series with the input line, and the coil energized with a smaller diode!.. Wrong polarity, no coil current, so no power to item. It also has a zero volt-drop advantage. Smaller items are catered for with a SERIES diode, the 0.7V volt drop rarely has any effect on smaller items, as they tend to be internally regulated to lower voltages anyway.