HELP Astron 70 amp PS
 

wrote in message
...
HELP Astron 70 amp PS
I have a astron 70 amp power supply and was hooking up a transmitter
to it and I pulled the power supply closer to me and the positive wire
came loose and hit the ground terminal on power supply.
Now when I turn it on you can hear the power supply turn on and the
light on the power swithch comes on, but no volts comes up on the
meter. I checked the terminals on the back and no volt, very little if
at all.
The outside fuse is good.
I took off top cover and I don't see and internal fuse.
Is there a diode I should be looking for?
I'm sure it has to have some kind of protection if the wires are
reversed.
Any help would be great.
Rich


Rich -

Well you shorted the power supply output. Normally the crowbar protection
circuitry cuts in and the fuse will blow.

First, NEVER open a power supply case/cover while it is still plugged into
the AC mains.

Second, ALWAYS properly discharge the electrolytic capacitors before poking
around inside a power supply. With a power supply of this amperage - it
will have one or two very large capacitors that will still have stored
energy after being turned off.

Now. Unplug the unit, come back in a couple of minutes (allow time for SCR
crowbar to reset) and then plug into AC mains and see if you have voltage.
If not, then some components have likely been damaged and will require
replacing.

If you have little technical skill, the I would recommend repair in a
"mentoring" process with an experienced technician.

A web site that may be useful for your troubleshooting is he
http://www.kbt-dc-supplies.com/index.php

Astron schematic diagrams
http://www.repeater-builder.com/rbtip/astron-index.html

The Astron power supply has an overvoltage protection circuit that will
clamp the output of the supply to near 0 volts when the power supply's
output has gone over the predefined voltage above normal. In most Astron
power supply's the point of overvoltage is near 15 vdc. When an Astron power
supply has gone into protect, it must be reset by turning off the mains
power to the supply for at least 10 seconds. This gives enough time for the
filter capacitors to bleed down so complete reset is possible. Protection in
the supply is afforded by the use of an SCR to crowbar the output when an
overvoltage situation has occurred. The circuit that fires the SCR is very
fast, and remains in protect mode until mains power to the supply has been
dropped for at least 10 seconds.

Greg, W9GB

"G.Beat" wrote in message
news:FSs3d.78590$D%.30566@attbi_s51...
wrote in message
...
HELP Astron 70 amp PS
I have a astron 70 amp power supply and was hooking up a transmitter
to it and I pulled the power supply closer to me and the positive wire
came loose and hit the ground terminal on power supply.
Now when I turn it on you can hear the power supply turn on and the
light on the power swithch comes on, but no volts comes up on the
meter. I checked the terminals on the back and no volt, very little if
at all.
The outside fuse is good.
I took off top cover and I don't see and internal fuse.
Is there a diode I should be looking for?
I'm sure it has to have some kind of protection if the wires are
reversed.
Any help would be great.
Rich


Rich -

Well you shorted the power supply output. Normally the crowbar protection
circuitry cuts in and the fuse will blow.

First, NEVER open a power supply case/cover while it is still plugged into
the AC mains.

Second, ALWAYS properly discharge the electrolytic capacitors before
poking
around inside a power supply. With a power supply of this amperage - it
will have one or two very large capacitors that will still have stored
energy after being turned off.

Now. Unplug the unit, come back in a couple of minutes (allow time for
SCR
crowbar to reset) and then plug into AC mains and see if you have voltage.
If not, then some components have likely been damaged and will require
replacing.

If you have little technical skill, the I would recommend repair in a
"mentoring" process with an experienced technician.

A web site that may be useful for your troubleshooting is he
http://www.kbt-dc-supplies.com/index.php

Astron schematic diagrams
http://www.repeater-builder.com/rbtip/astron-index.html

The Astron power supply has an overvoltage protection circuit that will
clamp the output of the supply to near 0 volts when the power supply's
output has gone over the predefined voltage above normal. In most Astron
power supply's the point of overvoltage is near 15 vdc. When an Astron
power
supply has gone into protect, it must be reset by turning off the mains
power to the supply for at least 10 seconds. This gives enough time for
the
filter capacitors to bleed down so complete reset is possible. Protection
in
the supply is afforded by the use of an SCR to crowbar the output when an
overvoltage situation has occurred. The circuit that fires the SCR is very
fast, and remains in protect mode until mains power to the supply has been
dropped for at least 10 seconds.

Greg, W9GB



The SCR DOES NOT fire on a short circuit condition. The SCR fires on
overvolage conditions, not over current. The current is sensed, and if
the current drain is exceeded, the output will fold back limiting the
current to maximum the supply is set for.

Now, the SCR might have falsely fired, and in that reguard you might
be correct in suggesting waiting several seconds with the power switch
off.

Peter

" Uncle Peter" wrote in message
news:njy3d.282268$Lj.181967@fed1read03...

"G.Beat" wrote in message
news:FSs3d.78590$D%.30566@attbi_s51...
wrote in message
...
HELP Astron 70 amp PS
I have a astron 70 amp power supply and was hooking up a transmitter
to it and I pulled the power supply closer to me and the positive wire
came loose and hit the ground terminal on power supply.
Now when I turn it on you can hear the power supply turn on and the
light on the power swithch comes on, but no volts comes up on the
meter. I checked the terminals on the back and no volt, very little if
at all.
The outside fuse is good.
I took off top cover and I don't see and internal fuse.
Is there a diode I should be looking for?
I'm sure it has to have some kind of protection if the wires are
reversed.
Any help would be great.
Rich


Rich -

First, NEVER open a power supply case/cover while it is still plugged
into
the AC mains.

Second, ALWAYS properly discharge the electrolytic capacitors before
poking
around inside a power supply. With a power supply of this amperage - it
will have one or two very large capacitors that will still have stored
energy after being turned off.

Now. Unplug the unit, come back in a couple of minutes (allow time for
SCR
crowbar to reset) and then plug into AC mains and see if you have
voltage.
If not, then some components have likely been damaged and will require
replacing.

[snip]

The SCR DOES NOT fire on a short circuit condition. The SCR fires on
overvolage conditions, not over current. The current is sensed, and if
the current drain is exceeded, the output will fold back limiting the
current to maximum the supply is set for.

Now, the SCR might have falsely fired, and in that reguard you might
be correct in suggesting waiting several seconds with the power switch
off.

Peter


Better to check the easy items first, before disassemblying the pass
transistors (2N3055 or 2N3771) to check them and replacing the LM723 ---
which are the usual suspects.

gb

Hi yes check the pass transistors and replace them with exact replacements or at least 2n5686 (full batch) if you wana invest longterm ......

Does any one have a copy of the rs 70 psu diagram i would appreciate it as the website i found is down and cannot be downloaded .. :-(
great day to all ..

repeaterbuilders.com has a copy for 70 amp it is listed under astron