[amsat-bb] Re: Azimute pointer on a G-5600 gives a wrong value

[i8cvs]

----- Original Message ----- 
From: "PE0SAT" <pe0sat at vgnet.nl>
To: "i8cvs" <domenico.i8cvs at tin.it>
Cc: "AMSAT-BB" <amsat-bb at amsat.org>
Sent: Tuesday, August 25, 2009 9:38 PM
Subject: Re: [amsat-bb] Azimute pointer on a G-5600 gives a wrong value
> 
> On Tue, August 25, 2009 19:45, i8cvs wrote:
> > 
> > Connect a voltmeter between terminals A1 and A3 of the control box
> > The voltage across the 500 ohm potentiometer into the azimuth rotator
> > must remain constant at about 6 volt while turning the azimuth.

> > 73" de i8CVS Domenico

> Hi Domenico,
> 
> As allways you give great answers :))
> 
> There is 9.2 volt DC :( looks that the 7806 is defect. But one thing
> that puzzles me, i don't see a connection from the negative site of the
> ac-dc diode bridge to ground.
> 
> 73's Jan
> 
Hi Jan, PE0SAT

OK the 7806 is defective and must be changed but since you have
to open the controller of G-5600 I suggest you to improve the
regulator performance because the original capacitor C9 0.01 uF at
the regulator output is a very small bypass capacitor. 

Solder a ceramic capacitor of  0.1 uF in parallel to an electrolitic
capacitor ranging from 1 to 10 uF and solder it both at the input
and as well at the output of the regulator as this cure will prevent
possible autoscillations of the regulator itself in a wide frequency
band.

The negative path of the bridge to ground for the regulator Q2 is
through series diodes D5-D4-D3 and ground so that a drop of about
0.6 x 3 = 1.8 volt is developed and this is made to get a minimum
voltage of 1.8 volt and not 0 volt when the wiper of the 500 ohm
potentiometer is fully grounded.   

The negative path of the bridge to ground for B1 C1 and B2 C2
to supply the +/- voltages to the operational amplifiers is through
the series transistor Q1 and zener diode D2

The negative path of the bridge for the coils of relay RY1-RY2-RY3
and RY4 is directly connected floating to the bridge and insulated
from the ground.  

Have fun and 73" de

i8CVS Domenico