[amsat-bb] Re: G-5500 7806 regulator question
Raul Romero CA3SOC
ce3soc at gmail.com
Sun Aug 17 10:21:47 PDT 2008
or you insert two diode rectifier in4001 or 1n4007 both ground 7805 and
one diode rectifier up 0.5 volt for 2 diode 1 volt up
sorry for my bad english
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----- Original Message -----
From: "i8cvs" <domenico.i8cvs at tin.it>
To: "AMSAT-BB" <amsat-bb at amsat.org>; "Mark L. Hammond" <n8mh at embarqmail.com>
Sent: Saturday, August 16, 2008 9:56 PM
Subject: [amsat-bb] Re: G-5500 7806 regulator question
> ----- Original Message -----
> From: "Mark L. Hammond" <n8mh at embarqmail.com>
> To: <amsat-bb at amsat.org>
> Sent: Sunday, August 17, 2008 1:54 AM
> Subject: [amsat-bb] G-5500 7806 regulator question
>> Hello All,
>> It appears that the 7806 voltage regulator in my Yaesu G-5500 control box
> has gone bad; the output is measuring more like 10.8 Volts (!). This
> explains why both position indicators were off by a factor of 2 (e.g.,
> elevation meter showing 90 deg, array pointing 45; azimuth meter showing
> deg, but array pointing 90 deg., and so on).
>> Question---has anybody used a 7805 to replace the 7806 regulator in this
> control box?
>> I don't have a 7806....so this brings the next question--anybody have a
> 7806 (or 2) that they want to sell?)
>> Mark L. Hammond [N8MH]
> Hello, Mark N8MH
> Each load across the 7806 regulator is represented by a 500 ohm
> potentiometer with in series a 15 ohm resistor.
> The load across the wiper of the 500 ohm potentiometer is 10 K
> and so it is not considered in the following calculation.
> If you replace the 7806 with a 7805 regulator the current flowing through
> resistor R= 15+500 = 515 ohm will be I= 5 / 515 = 0.009708 A and the drop
> of voltage across the 15 ohm resistor will be only
> V= 15 x 0.009708 = 0.145 volt
> Since the voltages for the AZ and EL instruments are supplied by the
> operational amplifiers Q3 and Q4 respectively you can adjust VR1 and VR2
> to get again a full scale indication.
> The 5 volt voltages for computer control are supplied by the operational
> amplifiers respectively Q3 for the AZ and Q4 for the EL so that when the
> AZ is rotated fully clockwise the potentiometer VR3 must be adjusted to
> exactly 5 volt DC on pin 6 of the external control 8 pin DIN connector and
> VR4 to get 5 volt DC on pin 1 when the EL is fully rotated by 180 degrees
> Looking the 8 pin DIN connector from the back of control box (external
> pin 6 is the first hole clockwise and pin 1 is the second hole clockwise
> It seems that a 7805 will work
> 73" de
> i8CVS Domenico
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