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Author Topic: ICOM IC-746 Low Power Output  (Read 3086 times)
WD4HMA
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Posts: 2




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« on: October 08, 2000, 09:57:48 AM »

 I have a new IC-746 with low power output.  It consistently produces between 65 and 75 watts out on all bands.  ICOM checkup says everything is ok.  Anyone know how to improve/correct this?
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AC5UP
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Posts: 3875




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« Reply #1 on: October 08, 2000, 10:52:38 AM »

Two possibilities come to mind:

You may have a sneaky SWR problem (like water in the coax or an oxidized connector) that's causing the SWR power foldback circuit to kick in at full power...

Or

Your power supply may not be up to the task. Even if the power supply is rated well above the needs of the radio, sometimes manufacturers fudge the numbers a bit by rating intermittent current peak rather than steady duty draw. Modes like FM, AM and RTTY all draw a steady current.

Even if the power supply is supposed to be adequate, a weak electrolytic can cause the supply voltage to drop at full load. Your supply may be capable of holding 13.8 volts at reduced power, but drop down to 12 volts or less on peaks.

And, a few years ago I was putting up an antenna and noticed a hole in the sheath of my brand new, name brand coax coming straight off the reel. Looked like a tiny football and was likely caused by an air bubble. It caught my eye when I saw a flash of copper in the sunlight.

Since that time I've gotten in the habit of eyeballing coax very carefully. It's the small stuff that gets ya'! (Hi)

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LA1SJA
Member

Posts: 55




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« Reply #2 on: October 08, 2000, 06:02:14 PM »

The most likely cause is that your power supply drops it's output voltage when you try run 100 watts out.
The best indicator is that you have the same problem on all bands.
I have a 746, and from memory, when you get 50 watts out you are down to around 11 volts.
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WD4HMA
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Posts: 2




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« Reply #3 on: October 08, 2000, 08:23:38 PM »

  The problem is not in the power supply or the load.  With a 30 amp load on the PS, the voltage is 13.7 volts.  The rig performs this way into different dummy loads (plural!), as well as an antenna.  Will not drive amplifiers to full power either.  Tried the same rig at a different ham's qth, same results.  I think the power output setting is low, but cannot find out where it is set, either in hardware or software.  
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KG6CIQ
Member

Posts: 50




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« Reply #4 on: October 09, 2000, 12:41:03 AM »

Hello,,

You might want to check out

http://www.vartel.com/icom746/icom746index.html

There are lots of threads on low output.

Rgds
David
ex G8LIY, DD5CK
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K5IQ
Member

Posts: 78




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« Reply #5 on: October 10, 2000, 03:23:50 PM »

Feel free to kick me in the shins for suggesting the painfully obvious, but have you checked the power output control on the front panel, bottom left, I think it's the second knob (I'm at work and can't see the rig), to make sure it's fully clockwise?

I only suggest this because I have been caught all too many times looking for complicated solutions to simple problems.  I once disassembled a rig trying to find why it suddenly stopped receiving only to find that the narrow filter switch was on, and there was no narrow filter installed!

Good luck!

Bob
K5IQ
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KA2UUP
Member

Posts: 388




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« Reply #6 on: November 14, 2000, 08:08:41 AM »

Along with K5IQ's suggestion, also check your MIC gain.  If it is set too low, output will be affected.  This is specially true when using the compressor function.  Good luck!

Bert, KA2UUP
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