gb wrote:
"xpyttl" wrote in message
news
Astron linear supplies use a 3 terminal regulator, usually an LM317.
These things do tend to fail from time to time. Can't tell if that's your
problem, but it is likely, and the things are cheap enough it's worth
popping a new one in to find out.



Really? What model of Astron linear power supply have you repaired or seen
that uses this design approach? I have never seen one like this -- over
past 20 years.
Confusing this with some other mfg. design?

Astron has been using the 14-pin (30 years old) LM 723 regulator IC with NPN
pass transistors (e.g. 2N3055, 2N3771) ... for as long as I have been
repairing them.

Check here for correct Astron information - repairs, etc.
http://www.kbt-dc-supplies.com/index.php

and Astron schematics (which show the LM723, not the later LM317 design)
http://www.repeater-builder.com/astr...ron-index.html

gb


I can confirm that mine has a 723, not a 317. Thanks for the web sites,
looks like some great information. I hooked up that headlight tonight
but it ran fine, pulling a bit over 3 amps for an hour or so. Maybe I
need more load to make it lose regulation.

Guess I'll start digging into that regulator board, the transistors and
all the big things like the transformer seem to be fine.

Thanks,
Kerry - WD5ABC

"Kerry Miller" wrote in message
news:UP_zf.140961$WH.46302@dukeread01...

I can confirm that mine has a 723, not a 317. Thanks for the web sites,
looks like some great information. I hooked up that headlight tonight but
it ran fine, pulling a bit over 3 amps for an hour or so. Maybe I need
more load to make it lose regulation.

Guess I'll start digging into that regulator board, the transistors and
all the big things like the transformer seem to be fine.

Thanks,
Kerry - WD5ABC

First, test each NPN transistor with a VOM or DVM ... both methods of proper
measurement are outlined (added proper method for DVM testing to procedures)

Second, discharge electrolytic capacitors before removing or inserting the
LM 723
Most Astron regulator boards have a socket for the LM 723, IF not after
removing, install socket - observing proper placement of pin 1.

Check bridge rectifier and diodes in circuit.

The KBT site suggests substitution of a resistor value. There are also
suggestions for bypass capacitors.

Stray RF in your radio shack can cause problems in some supplies.

gb

On Thu, 19 Jan 2006 23:47:24 -0600, Kerry Miller
wrote:

gb wrote:
"xpyttl" wrote in message
news
Astron linear supplies use a 3 terminal regulator, usually an LM317.
These things do tend to fail from time to time. Can't tell if that's your
problem, but it is likely, and the things are cheap enough it's worth
popping a new one in to find out.



Really? What model of Astron linear power supply have you repaired or seen
that uses this design approach? I have never seen one like this -- over
past 20 years.
Confusing this with some other mfg. design?

Astron has been using the 14-pin (30 years old) LM 723 regulator IC with NPN
pass transistors (e.g. 2N3055, 2N3771) ... for as long as I have been
repairing them.

Check here for correct Astron information - repairs, etc.
http://www.kbt-dc-supplies.com/index.php

and Astron schematics (which show the LM723, not the later LM317 design)
http://www.repeater-builder.com/astr...ron-index.html

gb


I can confirm that mine has a 723, not a 317. Thanks for the web sites,
looks like some great information. I hooked up that headlight tonight
but it ran fine, pulling a bit over 3 amps for an hour or so. Maybe I
need more load to make it lose regulation.

Guess I'll start digging into that regulator board, the transistors and
all the big things like the transformer seem to be fine.

Thanks,
Kerry - WD5ABC

I would look at the radio first. Put an ameter in the 12 volt line to
the radio and see how much current it is actually drawing.

73
Gary K4FMX

Gary Schafer wrote:

I would look at the radio first. Put an ameter in the 12 volt line to
the radio and see how much current it is actually drawing.

73
Gary K4FMX

Actually, I first thought it was an antenna problem, the rig acted just
like I had a bad problem with RF in the shack. I spent all of one
afternoon reworking the grounds and tuning the antenna. I've got the
best-tuned 4BTV in Texas! I tried it on a dummy load and had the same
problem. So, I pulled it off the power supply and ran the rig (Yaesu
FT-990) from the battery in my truck and it works fine. I also tried
the supply on a second rig, a TS-430, with exactly the same problem -
when I transmit the lights on the rig dim and it drops out of lock. The
430 is my mobile rig, it works fine in the truck but not on the PS.

I'll follow you guys' suggestions to start testing parts. I'm in a
fairly small town, so while I bought a 1000uf capacitor today at Radio
Shack, they can't even order an LM723 so I'll have to find someplace
else to get one.

Have any of you guys tried the new switching power supplies? I've seen
the one at Radio Shack (claims 25a but I doubt it), MFJ and Astron but
haven't ever used one. I normally just run 1 HF rig (max 100w) and a
small VHF rig (max 25w) for packet. Is a switcher solid and reliable
enough for something like that? I've considered getting something like
that and rebuilding the Astron when I can get the parts.

I have built regulated supplies but it's been 20 yrs since I tinkered
with anything analog, so I'll take all the help I can get! The info at
those links looks helpful, along with the ideas you guys have given me here.

73,
Kerry
WD5ABC

Kerry Miller wrote:

Have any of you guys tried the new switching power supplies? I've
seen the one at Radio Shack (claims 25a but I doubt it), MFJ and
Astron but haven't ever used one. I normally just run 1 HF rig (max
100w) and a small VHF rig (max 25w) for packet. Is a switcher solid
and reliable enough for something like that? I've considered getting
something like that and rebuilding the Astron when I can get the
parts.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You might be able to find a good deal on an Icom PS-125 switching power
supply. Icom had a promotion where they gave one away with each
purchase of an IC-746PRO. A lot of guys bought the '746 but didn't need
the power supply and I've seen many for sale as a result. I have one
and it's a great supply. I'm keeping mine :-) Check rec.radio.swap and
eBay.

Bill, W6WRT

In article GNhAf.141967$WH.127022@dukeread01, Kerry Miller
wrote:

Have any of you guys tried the new switching power supplies? I've seen
the one at Radio Shack (claims 25a but I doubt it), MFJ and Astron but
haven't ever used one. I normally just run 1 HF rig (max 100w) and a
small VHF rig (max 25w) for packet. Is a switcher solid and reliable
enough for something like that? I've considered getting something like
that and rebuilding the Astron when I can get the parts.

Kerry-

I have three switching supplies: One from Radio Shack, one from MFJ and
one from Icom (PS-125). They all work quite well as far as delivering
rated current.

The problem is that the high frequency switching noise can be picked up by
an HF receiver. The Radio Shack unit is TERRIBLE in this regard. The MFJ
is fairly good and the Icom is the best. Even so, the Icom switching
noise is picked up if it is anywhere near the antenna.

I'm currently using a makeshift indoor antenna consisting of a dipole made
of a pair of mobile whips on the second floor. Because of the noise
problem, I've gone back to using an old Kenwood linear supply with my Icom
756 Pro II. This radio has the band scope, so you can see the noise floor
increase across the band when the switching power supply is turned on.

73, Fred, K4DII

Fred McKenzie wrote:
In article GNhAf.141967$WH.127022@dukeread01, Kerry Miller
wrote:


Have any of you guys tried the new switching power supplies? I've seen
the one at Radio Shack (claims 25a but I doubt it), MFJ and Astron but
haven't ever used one. I normally just run 1 HF rig (max 100w) and a
small VHF rig (max 25w) for packet. Is a switcher solid and reliable
enough for something like that? I've considered getting something like
that and rebuilding the Astron when I can get the parts.


Kerry-

I have three switching supplies: One from Radio Shack, one from MFJ and
one from Icom (PS-125). They all work quite well as far as delivering
rated current.

The problem is that the high frequency switching noise can be picked up by
an HF receiver. The Radio Shack unit is TERRIBLE in this regard. The MFJ
is fairly good and the Icom is the best. Even so, the Icom switching
noise is picked up if it is anywhere near the antenna.

I'm currently using a makeshift indoor antenna consisting of a dipole made
of a pair of mobile whips on the second floor. Because of the noise
problem, I've gone back to using an old Kenwood linear supply with my Icom
756 Pro II. This radio has the band scope, so you can see the noise floor
increase across the band when the switching power supply is turned on.

73, Fred, K4DII
Thanks for the info. I picked up one of the RS supplies yesterday, and
you're right, it's pretty noisy on 80m, especially on my longwire which
terminates inside the shack. On 40m and above and on the outside
antenna (dipole or vertical) it's fine and below my noise floor. I
found a mod for it with some toroids and caps across the output to
filter it a little, I'll probably try that but it's workable for now
as-is since I don't work much 80m.

It will keep me on the air until I fix the Astron, I'll probably put the
Astron back on the HF rig and use the RS switching supply on VHF and UHF.

73,
Kerry
WD5ABC