"K4ERG" wrote in message
.. .

"A" wrote in message
x.com...


On Fri, 16 May 2008, Tio Pedro wrote:

Unless there are other major failures, the crowbar simply
puts the Astron supply into current limiting. I've had
50-amp supplies running in current limiting for days
because of noise-induced SCR firing.

If the supply crowbars because a pass transistor shorted,
then the crowbar location becomes a rather mute matter;
and involves a bit more than fuse changing.

Pete




Well, I've had a number of occurrences where, PTT on 2 M FM rig at
current well below current ratings and the output voltage goes to 0.5 or
less and had to off-on cycle the main switch. Makes me mad. Gotta get
back to that deep cycle 12 v battery.... They always go bad very very
very slowly. Great when there is a power failure, too! ;-)

Thanks to the rest of you guys that made comments, too.

You have stray RF in the shack. Check for intermittent connections to your
antenna. Most likely a bad shield connection inside one of the PL259
connectors or a bad ground connection.

Stupid spell checker!

On Sat, 17 May 2008, K4ERG wrote:


"A" wrote in message
x.com...


On Fri, 16 May 2008, Tio Pedro wrote:

Unless there are other major failures, the crowbar simply
puts the Astron supply into current limiting. I've had
50-amp supplies running in current limiting for days
because of noise-induced SCR firing.

If the supply crowbars because a pass transistor shorted,
then the crowbar location becomes a rather mute matter;
and involves a bit more than fuse changing.

Pete




Well, I've had a number of occurrences where, PTT on 2 M FM rig at current
well below current ratings and the output voltage goes to 0.5 or less and
had to off-on cycle the main switch. Makes me mad. Gotta get back to that
deep cycle 12 v battery.... They always go bad very very very slowly.
Great when there is a power failure, too! ;-)

Thanks to the rest of you guys that made comments, too.

You have stray RF in the shack.

Not likely if you've been running the gear for years and didn't touch
anything. see my response to your second post.

Check for intermittent connections to your
antenna. Most likely a bad shield connection inside one of the PL259
commuters or a bad ground connection.

On Sat, 17 May 2008, K4ERG wrote:


"K4ERG" wrote in message
.. .

"A" wrote in message
x.com...


On Fri, 16 May 2008, Tio Pedro wrote:

Unless there are other major failures, the crowbar simply
puts the Astron supply into current limiting. I've had
50-amp supplies running in current limiting for days
because of noise-induced SCR firing.

If the supply crowbars because a pass transistor shorted,
then the crowbar location becomes a rather mute matter;
and involves a bit more than fuse changing.

Pete




Well, I've had a number of occurrences where, PTT on 2 M FM rig at
current well below current ratings and the output voltage goes to 0.5 or
less and had to off-on cycle the main switch. Makes me mad. Gotta get
back to that deep cycle 12 v battery.... They always go bad very very
very slowly. Great when there is a power failure, too! ;-)

Thanks to the rest of you guys that made comments, too.

You have stray RF in the shack. Check for intermittent connections to your
antenna. Most likely a bad shield connection inside one of the PL259
connectors or a bad ground connection.

Stupid spell checker!


Not my idea but it sounded good when I heard it: "Life's too short for
spell checkers"

Ham radio advertisement many years ago: "Life's too short for QRP" and it
was for a big amplifier.

;-)

Hello everyone,

Regarding Astron Power Supplies, repair, retrofit, information and
modifications of the supply hardware and replacement Regulator Boards.

There are/were a number of different Astron Power Supply Regulator Board
versions made and configured. What is placed on the specific board is
related to it's capacity and type of operation. Depending on the year of
production, the size and the series the boards can and do change a bit.
Here's the url for the Repeater Builder web page,which has a lot of good
information:

http://www.repeater-builder.com/astr...ron-index.html

In some of the online yahoo groups I've mentioned some of the short
falls of the original Astron Circuit design and how I dealt with them.
Since that time I started selling replacment regulator boards with
updates and related information.

I offer a complete updated Astron Regulator board package, which is the
populated board and instruction sheet. The package also contains my
notes, information and various circuit diagrams. The price is $45 plus
the cost or US Priority Mail (about $4.35)

When your original Astron Board becomes problematic... my drop in
replacement is an updated clone of the original board with modern
improvements. Indeed Astron has included some of the mentioned
improvements onto some of their current regulator boards (but not all).
I've also addressed the fairly problematic crow-bar circuit layout and
part values to make the retrofit regulator board more stable. I've never
had one fail...

The variable supply is the same type board with part modifications to
allow adjustment of the output voltage within a practical range. The
ability to convert your specific supply to variable control is probably
more dependent on the date of mfgr of your regulator and the version of
your board. I have a list of each original Astron Regulator Board part
value based on size and the values on my replacement boards. If you've
charcoaled a part value I can supply the value information.

By Email and telephone I'm happy to help you trouble shoot your supply,
regardless of the mfgr. But my time is limited and I might not get back to
you right away so please be patient.

cheers,
skipp

skipp025 at yahoo.com
www.radiowrench.com

: Toby wrote:
: I have an Astron RS-20A, 20amp 12v fixed DC supply. I've heard that people
: have modified this model to become a variable voltage supply but have not
: found any schematics etc for this mod. Can anyone point me in the right
: direction? Thanks!

: Here is the schematic for a 35, it should ve similar to the 20 except for
: an extra pass transistor or two.
: http://www.repeater-builder.com/astr...tron-vs35m.jpg

No, it's different... and also dependent on the age of the supply. The
other size supply diagrams should be used as a guide only.

cheers,
skipp

The crowbar circuit operation should never damage the meter movements or
related sense resistors.

cheers,
s.

: geek wrote:

: I modded one of those significantly. Too long ago to remember the exact
: thing I did, but DO put that crowbar SCR anode on the collector of the
: pass transistors. If it trips as is, you kiss the current meter and
: expensive current sense resistor goodbye.

: Cheers,
: __
: Gregg

: And there should be a fuse in there to blow between the
: filter cap and crowbar.

No, a really bad practice... don't do it.

: The supply was actually 3rd world designed and made I swear.

Many parts/portions are done in Mexico...

: Better yet, put in a Resettable Circuit Breaker, as you can never find
: the right fuse, and they ALWAYS blow at the worst possible moment.....

No... you're asking for a serious problem and it's just a question of
when and not if.

cheers,
skipp

A number of gremlins cause the crow-bar to mis-fire. Just depends on
your specific regulator board version and part values used. One of the
reasons I came up with my replacment regulator board option.

http://www.repeater-builder.com/astr...ron-index.html

I've not seen a newer generation crow-bar circuit fail causing
equipment damage.. but as always your results might vary.

cheers,
s.

: A wrote:

: We had a thread recently on Astron power supplies and I thought I'd
: mention that I have an RS-35A (35 amps intermittent) for VHF brick
: amplifiers (main use) and I've had it for some 20 years. Recently, the PS
: has started to "crowbar" off on me (voltage goes to zero) and not even
: with high currents (maybe around 15 amps or so) and have to shut it off,
: wait a few seconds, and turn it back on.

: I also had another different regulated fairly high current DC PS go bad
: long ago, in a similar way.

: I'm wondering how many others of you have seen defective operation,
: sooner or later, or other deterioration in your high current regulated DC
: supplies?

: And, if the overvoltage crowbar craps out, it blows up your rig? I'm
: thinking of going exclusively back to deep cycle marine batteries, again.

Astron Power Supply Crow-bar Circuit Operation

: I'm wondering how many others of you have seen defective operation,
: sooner or later, or other deterioration in your high current regulated
: DC supplies?

Happens more with the older supplies... part values change with time.

: However operation of a crowbar should blow a fuse fitted 'upstream' of
: the pass transistors. As already explained earlier in this thread ,the
: crowbar should also be fitted 'upstream the pass transistors (but
: 'downstream' the fuse , while sensing the output voltage .

I don't agree...

: If the Astron voltage regulator would be suspect I would recommend a
: very simple circuit with a 7812 voltage regulator and a PNP transistor
: ,its output 'steering' the pass transistors .
: Ref : Experimental Methods in RF Design , by W7ZOI-KK7B- W7PUA
: page 1.15

Not a good idea... regulation really suffers bad.

: Instead of the 3 legged 7812 you can also use the similar LM317
: enabling output voltage adjustment
: After all this is a homebrew NG

No good... if you're only trying to get in the ball park maybe... if
you plan to use and trust the supply with expensive equipment you should
stick with an LM-723 or similar circuit properly designed using the mfgrs
data sheet information.

cheers,
skipp

: and if your really smart, you will dump the fuse, and replace it with
: a Resettable Circuit Breaker, because Murphy's Law states the Crowbar
: will do it's thing, ALWAYS at the worst possible moment, and the
: appropriate replacement fuse will be a 5 miles drive away, at the
: closest. You mileage may vary.....

The auto reset circuit breaker helps to start the fire, which takes out
the site/building. Not a good idea...

cheers,
s.