[amsat-bb] Re: G5500 az el issue resolved!

[Diane Bruce]

On Wed, Jul 27, 2011 at 06:45:34AM -0400, Jeff KB2M wrote:
>  Thanks to all for the refresher on the 5500 repair. I replaced the 17806P
> (which I think has a 6v output)  with a 7805. This fixed the problem. I had
> to recalibrate as my max readings in the SatPC32 rotor calibration routine
> dropped because of the assumed lower output voltage of the 7805 regulator. I

Put a pair of silicon diodes between the ground end of the 7805 and
actual ground. 

http://bybeelabs.com/uploads/J0308_Dac_Applications.pdf

I was going to suggest this trick before, but thought you had already
ordered a 7806. This will increase it to just about perfect. You might
even get away with a single diode.

While you are in there, don't forget to bypass the input and output with
a little more capacitance. The ceramic they have shown in the schematic is
insufficient. The 7806 itself can start oscillating making a noisy racket
all over HF and VHF. I used a 4.7uf since I had one lying around.

http://www.sunsunsun.net/kd4app/amsat/g5500.htm
 
- 73 Diane VA3DB
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