[ICOM] More on my Pro3 pwr issue

[Joe Dube]

I would try the power cord. I had a problem with the two fuse holders and 
after I removed them from the line problem solved. No more issues with the 
power to the Pro III.

Joe Dube K4TR
K4TR Antenna Mfg & Sales
www.k4tr.com
352-232-0281



----- Original Message ----- 
From: <kb4t at arrl.net>
To: <icom at mailman.qth.net>
Sent: Sunday, October 27, 2013 12:52 PM
Subject: Re: [ICOM] More on my Pro3 pwr issue


>I had a similar problem with my Pro3 several years ago. I found that the
> power cabling that goes between the rear power connector to the power amp
> module had developed an intermittent connection at the PA module. It's 
> been
> a while but my recollection is that the power connections to the PA module
> are made using crimp terminal lugs and screws. I solved my problem by
> removing (or loosening) the screws, removing the lugs from under the 
> screws
> and cleaning the lugs and the surface to which they connect. Once the
> surfaces were cleaned and bright, I reattached the lugs under the screws 
> and
> tightened. Problem solved.
>
> I concluded that the mating surfaces had developed some sort of film or
> something that introduced enough series resistance as current flowed to
> create a significant voltage drop. Cleaning the mating surfaces eliminated
> the series resistance under current flow and have not had a problem since.
>
> It was quite disconcerting to observe these symptoms. I confirmed that the
> power supply was not dropping voltage at the rear power connector so I
> pulled off the covers and traced the wiring to the PA module. It was at 
> the
> circuit board connections from the power supply that I found the voltage
> dropping. With only a mechanical connection between the circuit board and
> the wires, cleaning was the only solution.
>
> Essentially, one employs a "divide and conquer" troubleshooting process 
> that
> seeks to determine the root cause of the PA output power dropping. Likely
> causes are RF drive dropping, operating voltage dropping or devices 
> failing
> during operation. Doing the simple and easy stuff first makes sense. These
> steps are checking voltage to the active devices and inspecting for 
> obvious
> damage/opens in the voltage feed path. If the voltage remains at its 
> proper
> level when the transmitter is operated, you will need to look into the 
> drive
> level and device failure possibilities. Or send the radio off to a 
> competent
> tech.
>
> Hope this helps.
>
> 73,
>
> Frank KB4T
> Florida
>
>
>
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