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Author Topic: Icom 746  (Read 225 times)
K8OMA
Member

Posts: 22




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« on: April 20, 2004, 05:06:05 PM »

When transmitting the display goes blank but still lighted and power output is reduced
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K5LXP
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Posts: 4439


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« Reply #1 on: April 20, 2004, 05:14:44 PM »

Have you checked it into a dummy load?

Mark K5LXP
Albuquerque, NM

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K1CJS
Member

Posts: 5819




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« Reply #2 on: April 20, 2004, 05:25:00 PM »

My guess is you're probably pulling the input voltage down to a too low level.  If I'm not mistaken, the 746 needs a constant 20 amps--if your supply won't provide that you run the risk of damaging both the rig and the supply.  

Put a meter on the power input and see how low it goes down--BTW, don't depend on the rating of the supply, it may have a fault that is pulling the amperage down.
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K1CJS
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Posts: 5819




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« Reply #3 on: April 20, 2004, 05:26:13 PM »

Sorry, pulling the VOLTAGE down, not the amperage.
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K4AXX
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Posts: 87




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« Reply #4 on: April 20, 2004, 07:08:36 PM »

Have you checked it into a dummy load?

Mark K5LXP
Albuquerque, NM

Can you explain this answer you have given?
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K4AXX
Member

Posts: 87




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« Reply #5 on: April 20, 2004, 07:12:41 PM »

When transmitting the display goes blank but still lighted and power output is reduced.

I believe in the instruction manual reference is made to making sure you have a good ground attached to the 746. If not, display and other problems might well occur.
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K5LXP
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« Reply #6 on: April 20, 2004, 07:53:22 PM »

>> Have you checked it into a dummy load?

> Can you explain this answer you have given?

Given the lack of critical information needed to solve this problem, you have to start somewhere.  I gave K8OMA the benefit of the doubt that he knows how to run the radio, and it has operated correctly on whatever supply he has up until this point.  The power supply is a definite possibility but the antenna is more likely to be a variable than a power supply is.  Since this radio is computer controlled it is more subject to "wierdness" with RF on the chassis or coupling into the I/O ports.  Operating the rig into a dummy load eliminates the variable of an RF-hot environment, and will immediately prove or disprove the antenna side as a factor.  The antenna and power supply are the only two variables in this equation.  I picked the one to test that's more likely to be the issue.  

Mark K5LXP
Albuquerque, NM

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