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AvA757Pilot

Unable to tune COM/NAV radios in mid flight-737-800

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Everything was working fine as the flight started (KDFW-KDEN) but about 100 miles from Denver I was unable to change any of the radio frequencies or switch from standby/active. The mouse cursor responded and recognized the click areas but nothing happened when I clicked or scrolled.The NAV1 had been tuned to the ILS freq prior to this malfunction but did not capture it when I was in range. Everything else on the panel worked properly.Roger Curtiss

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Roger,I had a spell of this a few months back where I couldn't tune ILS frequencies and even if I did, the FMC kept saying 'Invalid ILS' or something. Not sure if yours is the same problem but the good boys at PMDG solved it. I had forgotten to switch the APU off after take off - and didn't select the right power source on the overhead. Result - draining batteries which apparently affects the radios. I used to find that it didn't happen on flights about an hour long, but over an hour - no radios.So in short after engine start-up, check APU is off (no blue lights or amber warning lights) and power from GEN1 or GEN2 is selected.

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Flip the battery on and off because it doubles as an avionics switch(i think). If that doesn't work look up the key command for the avionics master switch in the fs internal stuff.There is no true avioncs switch on the 737 ng, but it has to be "on" in order for the radio to work.

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Andyman---your suggestion worked once. Flipping the Standby battery switch restored the functionality.However, today I was on another flight and same thing happened but battery switch had no effect this time...so the problem is still there on occasion, but intermitent.Roger Curtiss

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Roger,did you check what I said about power settings in my response ?

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I did...I always turn off APU and APU Generrators and ensure that Engine Generators are on after engine start so I do not believe that was my problem.Roger Curtiss

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This radio "freeze" problem is now occurring every time I use an 800-900 model. The -700 works just fine so I am even more befuddled than before (if that is even possible!). Therefore, any insights would be greatly appreciated.Roger Curtiss

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