May 2000 Tower Trip
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Right after working perfectly for the MS Break Away, the 147.000 repeater lost output power.  On May 6, 2000, we removed the normal Power Amp (PA) to replace it with a temporary Exec II PA.   Here are some pictures of this trip up the tower.

Here's a summary of what lead up to this repair trip:

Since John, KU4GY is out of town, I thought I should update all of you on the status of the 147.000.

As some of you know, it was linked to 442.350 for the MS Break-Away. You should be proud, it worked great the whole weekend.

Sometime the next day, Monday, we noticed a very weak signal on the output. South end stations didn't notice as much, but it was very weak in North Dade. Timing couldn't have been better. A couple days sooner and it would have ruined the event for anyone with only 2 meter equipment. As we were preparing on Friday, I heard weak output, but it went back to normal after a bit. So it was pure luck that it held together for the event. Once it was determined that something was wrong with the PA on Monday, John shut down the repeater to avoid any further damage.

On Saturday, after the APRSC meeting, Lee, N4TCW and I went up the tower with Jason, KE4KYY as ground support. We removed the Mastr II Power Amp (PA) and installed a temporary Mastr Exec II PA I own. The usual PA can do 100 watts, but was running at 50 watts since we had more than enough coverage. The temporary PA is rated for 40 w and running at 20. I really don't think anyone will notice much of a difference. Maybe on the fringe areas. Everything worked fine on Sunday for the very successful SFFMA Picnic.

We suspect an open jumper between the PA PCB and the harmonic filter. This is a very common failure point for these PAs. The 146.76 has had this problem many times. Once it's fixed with a particular technique, it will stay solid. Otherwise, it fails every year or so. The temperature induced expansion and contraction of the PCB and the harmonic filter causes a lot of stress on this small jumper.

John, KF4ACN now has the defective PA and will repair and bench test it soon.

For pictures of our latest trip up the tower, go here:

http://www.sffma.net/may2000.htm

Thanks to everyone involved for their help with this repair.

 

Inside the cabinet.  Notice the severe rust inside the roof.    It's worse on the outside. 

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It may look like a mess, but that's the temporary PA on the left, the KD4BBM-6 digi on the right.   The device below is the exciter for the 147.000.   

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Here are the power supplies.  Astron 50A power supply for the 442.350 on the bottom.   Above that is the power supply for the 147.000.

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This is Lee, N4TCW.  Taken by Ray, KD4BBM from inside the elevator.  

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Here I, KD4BBM am, talking to Lee who's in the elevator.  This is the back of the rack.  The farms in the background give you an idea of how high we are.

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Just another shot of the farm land North of the tower.

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03/09/04

    South Florida FM Association, 2003   
   

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