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ASTRON RS35M Repair

KC0CF

Aug 1, 2011
2
Joined
Aug 1, 2011
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2
After a lighting strike to my tower, my Astron RS35M has a blown 8 amp fuse, I replaced fuse with a 6 amp and powered it up and blew fuse right away. Only physical evidence I saw was the -13.8 terminal has a 12 gague wire going to the bottom of the case near the rear left where a bolt and double nutted connection is made to chasis ground, I see a small black burnt residue there. I follow that back to what looks to be regulator board, where to start? Any one help a fellow ham lackie out?

Mike KC0CF


 
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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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A series of sharp photographs showing the damage would be a good start
 

paulmandel

Oct 11, 2010
3
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Oct 11, 2010
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I have fixed many Astron, in fact i have a RS-50A on the bench right now. A couple of things to check, First got to http://www.repeater-builder.com and download the Astron Schematic. I will warn you that the schematic is for reference and you may find part in the unit that do not exist on the schematic.

The half wave bridge on the board normally 1n5393 but they can be most anything. They are 1N5404 on the 50A supply. Check the two diodes first. If they are bad replace both and the 2200uf electrolytic capacitor. See if this stops the fuse blowing. If you want you can disconnect the transformer from the regulator board (all four taps) and make sure it is not the full wave bridge, but I have rarely seen this bridge out;

If the supply does not blow the fuse, but there is no voltage out, check pin 10 out of the regulator and see if there is 14v on the pin. Next go to the emitter of the Tip29 (this may be another transistor, but normally a Tip29) and see if you have voltage. If you do not there is a 1.8ohm resistor inline with the emitter that will open. Treat it like a fuse and replace it and you should have voltage at the output. If you have voltage, but it is not stable replace the .01uf disk cap from ground to pin 13 of the 723 regulator.

If it is still blowing fuses check the pass transistors.

Good luck,

Paul Mandel
 

KC0CF

Aug 1, 2011
2
Joined
Aug 1, 2011
Messages
2
I have fixed many Astron, in fact i have a RS-50A on the bench right now. A couple of things to check, First got to http://www.repeater-builder.com and download the Astron Schematic. I will warn you that the schematic is for reference and you may find part in the unit that do not exist on the schematic.

The half wave bridge on the board normally 1n5393 but they can be most anything. They are 1N5404 on the 50A supply. Check the two diodes first. If they are bad replace both and the 2200uf electrolytic capacitor. See if this stops the fuse blowing. If you want you can disconnect the transformer from the regulator board (all four taps) and make sure it is not the full wave bridge, but I have rarely seen this bridge out;

If the supply does not blow the fuse, but there is no voltage out, check pin 10 out of the regulator and see if there is 14v on the pin. Next go to the emitter of the Tip29 (this may be another transistor, but normally a Tip29) and see if you have voltage. If you do not there is a 1.8ohm resistor inline with the emitter that will open. Treat it like a fuse and replace it and you should have voltage at the output. If you have voltage, but it is not stable replace the .01uf disk cap from ground to pin 13 of the 723 regulator.

If it is still blowing fuses check the pass transistors.

Good luck,

Paul Mandel
Paul, wow thanks for the help! I will start the process and get back to you with my findings. Many good pointers and a great place to start. Thanks again .

mike KC0CF
 
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