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Author Topic: Icom IC-745  (Read 1069 times)
WA8MEA
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« on: December 17, 2010, 12:39:46 PM »


How long can the residual smell of burning circuitry last inside a rig?

73, Bill - WA8MEA
« Last Edit: December 20, 2010, 03:26:29 PM by Bill Lauterbach » Logged
WB2WIK
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« Reply #1 on: December 17, 2010, 01:55:16 PM »


How long can the residual smell of burning circuitry last inside a rig?


For a dog, forever.

What previously burned?
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K0BG
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« Reply #2 on: December 17, 2010, 02:48:53 PM »

Steve's probably correct, but there may be more to it.

Methanethiol (methyl mercaptan), is the stuff they put into our natural gas supply so common man can smell it. Most folks can smell the stuff in concentrations as low as .002 ppm. However, a select few of us, me included, can smell it at concentrations of less than .0001 ppm. You can add two zeros to that for most canines.

Methanethiol is actually a methyl alcohol. Methyl alcohols are used in the manufacture of some types of resistors. If your olfactory is extra susceptible to methyl alcohols, you might be able to smell it years later.

If you can, just consider yourself an old dog, just like Steve and I!
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K0BG
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« Reply #3 on: December 17, 2010, 03:35:15 PM »

Oh geez! I don't care what folks say, tomato juice doesn't work! We've got those critters all over Roswell, because so many folks feed the ferrel cats. For some reason skunks like cat food. I guess it is the fishy smell, but I can't say.

As for the beetles... We get those damnable carpet beetles down in these parts. About every 4 years or so, the darn things multiple faster than liberals at election time. and I don't care what you do, you can't keep those little critters out of everything. They're worse than the first liar on a fishing trip!
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WB2WIK
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« Reply #4 on: December 17, 2010, 03:44:46 PM »

If you are aware how computer power supplies are mounted inside the case, using an EXTREMELY thin piece of plastic on the bottom side of the power supply's circuit board, you would eventually find out that the little wires that stick out of the solder points start to poke their way through the thin vale of plastic and touch the metal chassis.  This happened on the 745 and two computers in our family.  I was lucky enough to save the 745 and one computer.  Another computer wasn't saved in time.

It was two resistors that bit the dust.  Poked through the thin vale of plastic and grounded out against the chassis.  Replaced the resistors and used spacers to mount the internal power supply away from the chassis.  Also covered the bottom of the circuit board with plastic, just to back-up my repair.

73, Bill

Aha!  You have the internal power supply.  I never had that in any of my IC-74X or 751 rigs.
In fact, although I remember it being an option for the 751/751A, I didn't even remember you could put a power supply inside the 745.  I guess you could.  I didn't remember.

Yes, that explains a lot.
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AC5UP
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« Reply #5 on: December 17, 2010, 04:44:28 PM »

Yes, Virginia... There really is a Skunk-A-Nator...

http://www.ktul.com/Global/story.asp?S=13680151
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WB2WIK
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« Reply #6 on: December 17, 2010, 07:24:38 PM »

We finally found out that the pet stores sell a shampoo that kills skunk smell.  It didn't get rid of the smell all at once, but it did it quicker and over less time than regular washings of the dog.

Cats, huh?  We have a lot of strays in our neighborhood.  Explains all of the skunks....

As far as the INTERNAL supply....yep....the 745 had one.  Flat as a board and almost took up the whole bottom of the transceiver.  Adding the spacers actually made putting on the bottom of the case a little more difficult.  Not much room to spare there....

73, Bill

Thanks for the reminder.  I had two 740s, a 745, and two 751s and none of them had the internal supply.  As I recall, I just didn't want that option because it seemed too far out at the time:  No proven reliability, and too small for the job.  I always used outboard power supplies with all these rigs.

Use yours in good health! Smiley
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WA0LYK
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« Reply #7 on: December 20, 2010, 08:23:41 AM »

I would probably worry about an electrolytic having gassed somewhere in the rig.  I replaced a number of them in my 745 a couple of years ago.  With its age, you could very likely be having the same problem.  There is a circuit board that has voltage regulators on it that is certainly a good place to look.  I also found several other "filter" ones on other circuit boards that were obviously leaking.  Now might the time to do a little PM and go over it pretty carefully.

Jim
WA0LYK
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K0BG
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« Reply #8 on: December 20, 2010, 11:20:36 AM »

I did mention about being an old dog, didn't I Bill?
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