Note: there is an Astron
Wireless Technologies company that manufactures some very nice antennas. It is a totally
separate operation with no connections to the Astron Corporation that makes power supplies.
|The contents of this page, like almost every page here
at www.repeater-builder.com, are totally dependent on donations of information.
If you have a hint or a useful trick please consider writing it up and sending it in.
Please consider sending us a scan if you have an Astron schematic that we don't list below.
If you don't have access to a scanner we can scan a good clean copy.
We have received emailed requests for schematics on the model BB-30M, SS-10 and SS-25 / SS-25M
supplies. Does anyone have any to share?
Astron makes both linear and switching power supplies, and some other products.
You should read this Astron Introductory
Information article before any of the other articles here in the Astron section
It has some very useful information on the Astron linear and switching power supplies, with
background, history, model-specific information, both repair and modification suggestions, photos,
The Pyramid Gold Series linear power supplies are
very similar in design and capacity to the Astron supplies. Both are based on the popular LM723
voltage regulator integrated circuit.
Articles and Modifications:
- Astron Linear Supply Battery Backup Modifications
All the schematics and modifications necessary to add a battery backup to your Astron linear
- Float Modification for the RS/RM-35A/S
Schematic of the Astron RS-35A/M with float
modification (the yellow highlighted area)
If you add a toggle switch to the front panel that shorts out the added resistor you can label it
"Float" (when off / open) and "Normal" (when on / shorted).
Make sure you print the mod sheet and tuck it inside the supply for the next guy...
- Adding Anderson PowerPole Connectors to an SS-30
supply By Robert Schulz KC6UDS
This is a very nicely done modification that extends the usability
of the SS-25 or SS-30 supply.
Kyle Yoksh KØKN took Robert's idea and modified
a Daiwa PS-304 power supply in a similar fashion.
- Adding Anderson PowerPole Connectors and Binding Posts
to an SS-25 supply By Neil Schwanitz V73NS
Other modifications to these small supplies, similar to the ones above.
- Reducing Inrush (Surge) Current on Astron Power Supplies
by Robert W. Meister WA1MIK
This modification adds a thermistor in series with the transformer, reducing the surge current
and eliminating annoying circuit breaker trips on the larger linear power supplies. This same
mod could be done to other high-power supplies.
- Installing a New Regulator Board in an Old Astron Power
Supply by By Tom Dailey WØEAJ
After the board burned up, Tom bought a new one from Astron. Seems they've made a few changes in
the design since his supply was made. This article describes what he discovered and how to deal
with putting a new board into an old supply.
- An evaluation of a 2009 Astron RS35M supply
by Stu Martin K2QDE (2.5 MB PDF)
Stu opened his brand-new supply and took several photos, showing what's been added or changed.
He scanned then redrew and corrected the schematic so it matched the actual unit; this drawing
can be found as a PDF file below.
- Replacing Astron Meter Lamps
by Larry Lockard N7FM (off-site link)
A very well-written article that shows how he replaced the "unreplaceable" internal meter lamps,
which seem to be two 14V bulbs wired in series and powered by the raw unregulated voltage.
- Restoring / Rebuilding an Astron RS35M
by John Keith W5BWC (1.4 MB PDF)
While this is listed as a "restoration" it's actually a complete gut job with only the
transformer and chassis remaining. Everything else gets replaced with a completely different
- Repairing Astron 13.8V Linear Supplies
by Robert W. Meister WA1MIK
General linear power supply circuit explanation, followed by the most common problems,
diagnostic techniques, and repairs for these units.
- Crowbar SCRs in Astron 13.8V Linear Supplies
by Robert W. Meister WA1MIK
A summary of SCRs used by Astron and some available replacements.
- Upgrading the Astron
Over-Voltage Crowbar Circuit by Rich Post KB8TAD (off-site link)
Repairing a supply, analysis of key circuits, and replacing the SCR crowbar with MOSFETs.
Very well written and chock-full of troubleshooting information.
- Annotated RS35M Schematic
by Jim Larsen AL7FS (169 kB PDF)
Jim Larsen, AL7FS (the ARRL Alaska Section Manager) took that QST article and the schematic
and produced an annotated schematic that takes advantage of the annotation function of the
PDF file architecture. Use a recent version of the Adobe Acrobat reader and just mouse over
the yellow folder symbols. Worth studying.
- RS-50A / RS-50M / RM-50A / RM-50M Service Manual
by Astron, transcribed by Bob WA1MIK (130 kB PDF)
Specifications, circuit description, theory of operation, servicing, adjustments, parts list,
schematic for the 50A rack-mount and desk-top power supplies.
- Installing Digital Meters
in an Astron Supply by Tony King W4ZT (SK) (833 kB PDF)
Tony bought a used astron that had both meters "stuck". He replaced them with digital meters
and created a web page about installing them. The meters he bought were a type that required
an isolated power source for the ammeter, and the article includes a schematic and photo of
the isolated 5vDC source that he build on perfboard.
- Replacing or Adding Digital Meters to
Astron 13.8V Linear Supplies by Robert W. Meister WA1MIK
An overview of the various meters you can buy and which ones seem to work the best in
popular Astron supplies.
- Adding Voltage and Current Adjust Pots to an Astron
13.8V Linear Supply by Robert W. Meister WA1MIK
Turn an RS-supply into a VS-supply. Simple to do and easily reversible. Implement one or both.
- Parallel Operation of Astron Linear Power
Supplies by Robert W. Meister WA1MIK
The secrets of that "For Parallel Operation Only" binding post on the rear panel.
- If your regulator board is beyond repair, you can buy a brand new one from Astron for
$20US plus shipping. They'll even ship it to you and let you remit payment after you receive
it. Tell them the supply model number and they'll customize it for you. Here are 300kB photos
of the component side and the
solder side of a brand new regulator board ordered in 2014
for a VS35 power supply, courtesy of Bob McKinlay VE3DJ. The blue adjustable potentiometer
marked 1K on the board adjusts the power supply's maximum output voltage.
Power Supply Model Information:
Please realize that you will find multiple different schematics listed below for the same
supply as the designs changed over the years due to parts availability, circuit improvements,
etc. For example, the early supplies use discrete stud-mounted diodes instead of half of a
bridge rectifier (switching to an epoxy bridge module, despite the fact that only half is
used, is one of the tricks that the designer at Astron used to lower the parts cost and
manufacturing labor cost). You may have to download more than one schematic to get the one
that matches your supply, and you may not find your schematic at all (as we only have the
ones that were donated to us). If you have one that we don't, please consider sending us a
scan or a Xerox copy.
We have received emailed requests for schematics on the model BB-30M, SS-10 and
SS-25 / SS-25M supplies. Does anyone have one to share?
When (or if) you find the schematic that matches your unit I suggest you print it and stuff
a copy inside a plastic page protector, and tape it to the underside of the lid of the power
supply cabinet! Several folks have mentioned in emails and on mailing lists that you can call
Astron on the phone and you will hear them tell you that they don't have electronic copies of
their drawings and they don't know how to email them. Trust me, the person that answers the
phone will be amazed when you tell them that the drawings from different years for the same
model power supply show some different component IDs and values. Unfortunately this is
important because if one chooses to buy replacement parts (from Astron) they (according to
Astron) need only to supply the model and component IDs... Fortunately everything but the
filter caps, transformer, and sheet metal are common Mouser or DigiKey parts. And I bet you
could find the capacitors if you tried hard enough. Astron has to get them from somebody.
So leave off the prefixes and suffixes and first look for the basic model number as opposed
to the specific model.
- An "RS-" prefix is a standard desk-top power supply. I suspect that RS stands for
- An "RM-" prefix instead of "RS-" prefix indicates a Rack-Mount power supply (i.e.
packaged to mount in a 19 inch rack). This packaging is only offered on the larger
supplies. If you need to rack mount a smaller one, just use a rack shelf. Usually
there is little (if not zero) electronic difference between the RS- series and the
similar RM- model.
- Change the first letter from R to V and you have one with front panel adjustments
(V=variable). Converting a RS or RM to a VS or VM usually involves adding two
potentiometers to the front panel and making the wiring changes shown in the schematic.
See the article elsewhere on this page.
- SS- series are Small Switching power supplies. Their schematics are further down the page.
- SL- series are Small Linear power supplies. Their schematics are further down the page.
These have room for a two-way radio to be mounted inside the cabinet. The SL series suffix
indicates the make/model radio they were made to work with. Check the catalog pages on
Astron's web site for all the details.
- LS- and VLS- series are Linear Special-voltage power supplies, usually 28 volt.
- SLS- are Switching Special-voltage power supplies, usually 28 volt.
- A trailing "M" indicates front panel Meters. Newer supplies (possibly starting around
2008) have illuminated meters. If the supply has the "M" suffix, those under 20A usually
only have room for just one meter. 20 and 35A supplies could have one or two meters. 50A
and larger supplies almost always have two meters. Slim-line (SL) supplies usually don't
have room for meters. 25A and larger switching supplies usually have two meters.
- A trailing "L" indicates there's a cigarette Lighter socket on the front.
- A trailing "S" means there's a Speaker inside the case.
- A trailing "BB" indicates the Battery Backup option.
- A trailing "RM" indicates Rack Mount, often for dual supplies.
- A trailing "220" indicates the supply operates on 220-240V line voltage.
Astron builds supplies for several manufacturers - for example a Kenwood KPS-12 is based
on the Astron RS-12, the Motorola RRDN6933A is an RM-35A-BB and
the Motorola HPN9041 (45 kB PDF) is an
RS-20 variant. Astron also builds custom supplies for Motorola, GE, Icom, E.F. Johnson,
Kenwood, Uniden and Vertex. For example, the Astron SL-11RRA is a 13.8 Volt 11 Amp unit
specifically designed with a metal sleeve built into the on top of the cabinet. The sleeve
is sized so that a MaxTrac, Radius or GM300 mobile can slide into it;
here for a photo).
A conversion list of Motorola to Astron model numbers can be
Donations of additional schematics for the library below are always
Send them to the maintainer listed at the top of this page (you will be credited unless you
tell us not to).
See the "Notes" section above for an explanation of the prefix and suffix letters.
If you don't find the schematic for your Astron below, then we were not given it. If you find
one somewhere else that we don't have, we'd appreciate a scan.
Astron model numbers indicate the peak (intermittent) current that can be drawn from the supply.
The continuous current is somewhere between 50 and 80 percent of the peak current. For example,
an SL15M is rated 14A peak but only 7A continuous, yet an RS20A is rated 20A peak but only 16A
continuous. The absolute maximum current where foldback limiting occurs is usually 10 to 30 percent
above the peak current rating.
The available output current on VS supplies depends on the output voltage. You get much less
current at a lower voltage. For example, a VS50M supply is rated for 37A continuous at 13.8VDC
but only 22A continuous at 10VDC and only 10A continuous at 5VDC output. The other VS supplies
must be derated similarly. This has to do with the power dissipation capability of the heat
sinks and transistors on the back and sides of the supply. At lower output voltages, there's
more voltage across the transistors, so they get much hotter. Current foldback may also occur
at these lower current ratings, so beware. The Astron catalog has these derated current specs.
Important Note: Numbers in many of the schematics below, particularly the pin numbers on
the 723 regulator IC, may be blurry. There is nothing connected to pin 8, so if you see something
that looks like an "8" it's most likely a "6" where the top got closed up. The voltage charts on
most of the schematics follow this scheme. Check some other schematics if you can't read the one
for your particular supply as they're very similar.
Linear Power Supply Schematics:
- RS-3A and RS-4A 364 kB, dated 12-89
donated by Oscar Ramsey NV3G
(The draftsman obviously started with the RS-7
schematic... he forgot to adjust the voltage table... it shows a 7 amp load...)
- RS-7A 70 kB, dated 10-94 donated by Mike
- RS-10A, RS-10S 105 kB, dated
09-81 donated by Bill Netzlof KL7IGB
- RS-10A, RS-10S 368 kB, dated
09-88 donated by George Franklin WØAV
- RS-12A 199 kB, dated 11-83
donated by Richard Reese WA8DBW
- RS-12A, RS-12M 125 kB, dated 06-88
- RS-12A, RS-12M 41 kB PDF, dated 06-88
- RS-12A-BB 119 kB PDF, dated 01-2000
donated by John Lund. See the comments above on the battery backup feature.
- RS-12A, RS-12M 52 kB PDF, dated
11-2009 donated by Greg Shaw N4GOS
- RS-20A 71 kB, dated 11-78
donated by Gary Eldridge KC8UD
- RS-20A, RS-20S 79 kB, dated
09-88 donated by Kevin Custer W3KKC
- RS-20A, RS-20S 185 kB, dated 09-88
- RS-20A, RS-20S 44 kB, dated 01-2000
donated by Ron N8HXR
- RS-20M 117 kB, dated 01-2000 donated
by Ron N8HXR
- RS-20A-BB, RS-20M-BB 330 kB, dated
01-2000 donated by Rick Williams N8EDR See the comments above on the battery
- VS-20M 26 kB PDF, dated 11-78
- VS-20M 80 kB PDF, dated 09-86
- VS-20M 78 kB PDF, dated 01-2000
donated by Larry Horlick VYØHL
This supply is also known as a Motorola RRDN6082A. The Moto invoice says "VS-20ML".
- RS-35A 135 kB, dated 01-78
donated by Joe McIntyre W4DEX
- RS-35M 46 kB, dated 04-87
donated by Kevin Custer W3KKC
- RS-35A, RS-35M 216 kB,
dated 04-87 but different. Donated by Mike Morris WA6ILQ
- RS-35M 47 kB, dated 04-87,
again different. Donated by Mike Morris WA6ILQ
Thanks to Ed Lambert K1ZOK who pointed out that there was an important error in
this schematic file (the repeater-builder staff edited the image file and corrected
it). There was an extra "line" drawn between the collector of the TIP29 and the
base connections of the pass transistors. This, effectively, shorted out the
regulator driver Q2. If you downloaded this schematic in the past you may want
to get a fresh copy and replace your incorrect copy.
- RS-35A, RS-35M 555 kB PDF, dated
09-88 donated by Jim Bacher WB8VSU
- RS-35A, RS-35M 159 kB PDF, dated
05-91 donated by Mike Morris WA6ILQ
- RS-35A, RS-35M 46 kB PDF, dated
05-95 donated by Mike Morris WA6ILQ
- RS-35M 498 kB, dated 01-2000
- RS-35M 78 kB PDF, dated 10-2009
redrawn, corrected, and donated by Stu Martin K2QDE
This is probably the newest, most up-to-date schematic available. Includes meter
- RS-35M 127 kB PDF, drawn by Larry Joy WN8P
This is an actual as-built schematic, drawn from scratch to current IEEE specifications,
of an older (circa 1978?) RS35M supply with one meter on the front, stud rectifiers, and
the TIP29 driver transistor and the crowbar SCR mounted to the chassis (current models
have those parts on the regulator board).
RS-35M Detailed Parts List 56 kB PDF,
goes along with Larry's schematic diagram above. Lists every piece of wire and hardware.
- VS-35M 37 kB PDF, dated 01-87
donated by Steve Duncan, WA4ITA
- VS-35M 503 kB PDF, dated 01-2000
donated by Bill Neuman, WB9EFP
- RM-35A, RM-35M 33 kB PDF, dated
01-13 donated by John D'Errico, N1ERF
- RM-35A-BB 80 kB PDF, dated 01-93
donated by Larry Horlick VYØHL
This is a factory Battery Back-Up supply that is also known as a Motorola RRDN6933A.
See the comments in the battery backup section above concerning this particular supply.
- RS-50M 181 kB PDF, dated 01-2000
donated by Kevin Custer W3KKC
- RS-50A, RS-50M, RM-50A, RM-50M
36 kB PDF, dated 03-96 donated by Tom Allinson WB6DGN
- VS-50M 25 kB PDF, dated 08-82 donated
by Bob Shields KA9TYL
- VS-50M 74 kB PDF, dated 11-95 donated
by Tim Bovard, Senior Technician at Nichols & Simpson, Inc.,
Organbuilders in Little Rock, Arkansas.
- RS-50A-BB, RS-50M-BB 127 kB, dated
07-95 donated by Robert Burton KD4YDC See the comments above on the battery
- RS-50M-BB, RM-50M-BB 45 kB PDF, dated
07-2011 donated by Roger Gray N5QS
- RM-60A, RM-60M 43 kB PDF, dated
08-88 donated by Tom Allinson WB6DGN
- RS-70A, RS-70M 73 kB, unreadable
date (probably 08-88) donated by Mike Morris WA6ILQ
- RS-70A, RS-70M 227 kB, dated
06-97 donated by Avent Lane
- RS-70A, RS-70M 74 kB PDF, dated
01-2007 donated by Tom Allinson WB6DGN
- VS-70M 38 kB PDF, dated 06-95 donated
by Brian Palmersheim KBØETC
Slim-Line (Low-Profile) Linear Power Supply Schematics:
- SL-11A 99 kB PDF, dated 04-90
- SL-11A, SL-11R 172 kB,
dated 11-2009 donated by Paul Mandel W4PGM
- SL-15 51 kB PDF, dated 04-90
donated by Ed Lambert K1ZOK
- SL-15R 184 kB, dated
11-2009 donated by Dave Christensen KD7UM
28 Volt Linear Power Supply Schematics:
- LS-25A 28 Volt, 25A
intermittent, 18A continuous, linear power supply 39 kB PDF, dated
04-2004 donated by Astron.
A no-frills 28V power supply similar to the RS-50 supply but with twice the
output voltage and half the output current. This supply is also sold under
the Uniden name as their model ARX 330.
- LS-35M 28 Volt, 35A intermittent,
25A continuous, linear power supply dated 07-93
Found on the web. Has some voltage measurements on it.
- VLS-10M 28 Volt, 10A intermittent, 7A
continuous, linear power supply 41 kB PDF, dated 01-1990
Donated by Roger Gray N5QS.
- VLS-35M 28 Volt, 35A intermittent, 25A
continuous, linear power supply 58 kB PDF, dated 06-1995 donated by Ron
Similar to the VS-70M supply except for the output voltage (variable from 5 to
32 Volts) and current.
Switching Power Supply Schematics:
- SS-12 42 kB PDF, dated 08-96 donated by Eric
No parts values other than what Eric noted.
- SS-18 47 kB PDF, dated 11-98
- SS-25M, SS-30M 483 kB PDF dated
Shows meters and the 120V/240V input power selection switch.
- SS-25M, SS-30M 1.7 MB PDF dated
Four pages long, no voltage selector switch, but shows illuminated meters. It also has a
very detailed parts list at the end.
- SS-30 71 kB PDF, dated 09-2000 Donated by Eric
There is minimal parts info on the schematic. Further info is available
- SS-30 157 kB PDF, dated 09-2000
A second copy of the same schematic, but a little more readable.
- SS-25M, SS-30M with enhancements 914
kB PDF donated by Alan Sewell N5NA
Alan had to repair one of these. In the process he corrected the schematic, added LOTS of
parts values and other notes, and took extensive voltage readings at various points, complete
with photographs. Excellent documentation.
- A mod for the Astron SS-25 and SS-30 power supplies (and maybe other SS-series) from NU4G:
These two power supplies use a simple normally open "click" thermostat to switch a very noisy
(acoustic noise, not RF noise) fan on and off. The fan noise can be annoying at times, so I've
modified my supplies to make it less so. Open the supply after first disconnecting AC power and
allowing for DC voltage to bleed down. Looking inside you will see two sets of heatsinks near
the rear of the unit. Each heatsink has a thermostat, the left side heatsink has a normally
closed 50 degree C thermostat for the AC input - don't bother it. The right side heatsink has
the fan thermostat mounted to it. The fan thermostat switches DC from the output to power the
fan. If you bridge the thermostat with a two watt resistor of 75 to 100 ohms the fan will be on
continuously, but very slowly. This slow speed is enough to keep the supply cool with very little
noise. Before installing this mod simply running my 756PII on receive was enough to turn on the
fan every 5 minutes or so. With the mod I've only had the fan go to full speed (i.e. the
thermostat closed) while operating RTTY for an extended time on a very warm day.
This mod may or may not apply to other models of Astron switching power supplies.
Switching Regulated Voltage Converter Schematics:
- 1212-18 199 kB PDF donated by Tom
This unit allows you to use a negative ground +12v device (like a two-way radio) on a -12 volt
battery system (i.e. a 12v positive ground vehicle). The positive side of the input and negative
side of the output is common. Another way of saying it is that this is a ground inverting
- 2412 49 kB PDF donated by Ed Lambert K1ZOK
This unit allows you to use +12v devices (like two-way radios) on +24 volt battery systems
(found in many Kenworth, Peterbilt and other large commercial vehicles such as fire trucks).
The negative side is common.
- 2412 V3a 91 kB PDF donated by Mike
Collis WA6SVT, who reports: This unit has a "Low Voltage Disconnect" built in but it's
set to drop out at 18 volts. This may work great for an 18-wheeler truck driver wanting
the unit to provide 13.8 volts out on a nearly dead battery, however you might not want
to run your battery down so low, especially at a solar power site. A slight modification
will raise the dropout point to save a battery bank at a solar site. To do this, change
the 62k resistor (R17) on the voltage divider between the input voltage and ground that
supplies voltage to pin 16 (UVLO) of the LM5025B chip. When this pin is below 2.5 volts,
the converter shuts down; above 2.5 volts, it turns on. There is hysteresis on this pin
to prevent chattering (about 2 volts difference between off and on). Changing R17 to 91k
will move the Low Loltage Dropout to 22.75 volts and re-connect at just under 25 volts.
If you desire an adjustable dropout, add a 30k trim pot to the board in series with the
existing 62k resistor.
Back to the top of the page
Back to Home
This page originally created in August 2000 by Kevin Custer W3KKC
Totally rewritten and a number of schematics added on 10-14-2004 by Mike Morris WA6ILQ
Copyright © 2000 and and date of last update by Repeater-Builder.com
The following people contributed information to this web page
(in alphabetical order by last name):
Greg Allison KZ6S (SK),
Tom Allinson WB6DGN,
Jim Bacher WB8VSU,
Don Best N6ALD,
Robert Burton KD4YDC,
Henry Clark KC4KZT,
W.C. Cloninger, Jr. K3OF,
Steve Duncan, WA4ITA,
Rick Eastwood W6RE (ex KB6LJO),
Gary Eldridge KC8UD,
George Franklin WØAV,
George Henry KA3HSW,
Larry Horlick VYØHL,
Jeff Kincaid W6JK,
Ed Lambert K1ZOK,
David Leeper K6DWL,
Eric Lemmon WB6FLY,
Doug Marston WB6JCD,
Skipp May WV6F,
Bob Meister WA1MIK,
David Metz WAØAUQ,
Brian Palmersheim KBØETC,
Mike Perryman K5JMP,
Richard Reese WA8DBW,
Ron Rogers WW8RR,
Robert Schulz KC6UDS,
Bob Shields KA9TYL,
JaMi Smith KK6CU (SK),
Ron Vincent KF4D, and all those
who chose not to be identified.
The Astron logo/image is a registered trademark and is used within this page with
permission from the Astron Corporation.
The schematic images are copyright © Astron Corp. Each one is dated on the
individual drawing. No copyright infringement is intended. If Astron had the schematic
library on their web site we wouldn't need to.
This web page, the hand-coded HTML on it, this web site, the information presented in
and on its pages and in these modifications and conversions is © Copyrighted 1995
and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All
Rights Reserved, including that of paper and web publication elsewhere.