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 one 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, and more.

Astron Linear Power Supply Reset Circuits

• An external reset circuit for the Astron Linear series     A reset circuit by Kevin K. Custer  W3KKC
• An internal reset circuit for the Astron Linear series     A reset circuit provided by The Astron Corporation - they call it the OVPR-12V - by Kevin K. Custer  W3KKC
  If you are inside your Astron for some other reason it's worth adding this circuit as long as you have the cover off... Just remember to print the page and leave a copy inside the case so the next guy will know what the little circuit on the piece of perfboard is for.
• Astron's own writeup on the OVPR12V   55 KB PDF donated by Joe Orrico WB6HRO
  Astrons documentation shows a extra LED indicator.

Astron Linear Power Supply Articles and Modifications

• 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.
• 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 (2.5MB 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 (1.3MB 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 design.
• 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.
• Annotated RS35M Schematic   by Jim Larsen AL7FS (170kB 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 fuction of the PDF file architecture. Use a recent version of the Adobe Acrobat reader and just mouse over the yellow folder symbols. Worth studying.

Astron Linear Power Supply Battery Back-up Modifications

If you inspect the circuit diagram you will see that the BB option is simple - it consists of a pair high current diodes wired cathode to cathode, with one anode going to the supply, and the other to the battery bank, and the cathodes feeding the load. This configuration allows either the power supply or the battery to feed the load. In the low current supplies they use half of a bridge rectifier, in the high current supplies they use two separate diodes in parallel for each current path. The charging circuit is not well designed as it is just a single resistor from the battery to the output of the supply (look for R103 in the schematic for the RS‑12‑BB and RM‑35A‑BB)... and this overly simple charger circuit can boil your battery dry! Since this design uses the supply voltage as the charging voltage you must have the supply voltage set EXACTLY to the voltage that is the sum of the diode voltage drop plus the battery float voltage... regardless of what the voltage your load wants to see (and the voltage drop across a diode varies somewhat from low-load to full-load). Overly simple charging circuits ALWAYS leave lots of room for improvement.

The rule of thumb on maximum charging current for nickel-cadmium or lead-acid batteries is no more than 1/10 of the amp-hour capacity of the battery. Therefore a 20 amp-hour battery has a maximum charging current of 2 amps.

There are two major flaws with the Astron charger design:

• First, the charging current is limited only by the voltage difference between the Astron voltage output and the voltage of the battery limited by a series resistor. That resistor has a value of 10 ohm 10 watts in the RS-12-BB, 5 ohms 10 watts in the RS-20-BB or RM35-BB or 1.6 ohm 15 watt resistor in the RM-50-BB (and that resistor is made from three 5 ohm 10 watt resistors in parallel). Under conditions of a dead battery the initial charging current can be higher than the battery can take - in the RM-50-BB that 1.6 ohms at 14v delivers between 8 to 9 amps (and that's not documented anywhere). On a RS-12-BB the max charging current is about 1.4 to 1.5 amps... The three RS-12-BBs I have seen at radio sites have all been tied to batteries in the range of 7 to 20 amp-hours. Do you see a potential overcharge problem with the 7 amp-hour battery?
  
  As mentioned above the maximum charging current is less than 1/10 of the amp-hour capacity of the battery. Therefore a 20 amp-hour battery has a max charging current of 2 amps. The RS-50-BB charge current into a dead battery is 8 to 9 amps? Oops.
  
  
• The second flaw in the Astron design is that the 8 to 9 amps flowing through the charging current limiting resistor in an RS-50-BB dissipates around 100 watts.... oops, POOF! There goes the three paralleled 5 watt resistors. Now you have no battery charger and who knows what was damaged with the excess heat from the fried resistors.

Now in real life, the battery voltage is not going to be zero, so the difference voltage is not going to be the full Astron output of 14 volts and the charging current is going to be less than 8 amps, but still... there are better charging circuits out there than a 14 volt 50 amp power supply and a single undersized current limiting resistor.   Especially with the extra requirement that the supply voltage has to be set to the battery plus the series diode voltage drop (no matter what voltage the load - your repeater system - wants to see).

If you need a battery backup system for your repeater, I would do one of two things:

• First, leave out that charging resistor (R103 or its equivalent in larger supplies) and use an external multistage charger outside the housing of the Astron.   There are good ones out there, I've had excellent results with a high-end "Battery Tender" made by Deltron Corp.
• Second, replace R103 with a multi-stage charger board added inside the Astron cabinet.

I've seen an Astron where the owner mounted a DC toggle switch (I'd use a toggle-type-circuit breaker) of the appropriate amps rating on the front panel of the supply near the diodes, wired it in series with the R103 charge current control resistor and labeled it as "Internal Charger Enable / Disable".

If you are going to "roll your own" high current BB conversion, and you don't mind a "non-pretty" implementation, then a part of the diode array from a high-current alternator will work just fine.   The normal "12 volt" automotive alternator diode array has six diodes in it (or sometimes 12 in 6 groups of 2 in parallel or 18 in 6 groups of 3 in parallel), and the metal plates with the diodes mounted in them are usually tossed in the trash if one diode is dead.   A long time ago I needed to swap out the alternator in my old 1971 Dodge Dart DEA undercover chase car... (that was a FUN car to drive...)   I used the visit to the alternator rebuilder to pay $5 for a three-diode common-cathode array out of a 120 amp alternator that had one bad diode that was on the end of the plate.

When I got home I mounted the diode plate in a bench vise and used a drill and hacksaw to remove the bad diode out of the end piece.   This gave me two good diodes and enough space around the diodes to allow drilling a couple of mounting holes.   Using that diode plate mounted on standoff insulators I ended up with the same circuit as the Astron BB option at a cost of $5 plus the standoffs... and in the proof-of-concept prototype the plate was held to two pieces of wood by some drywall screws. The final version used polystyrene rod for the insulators.   All of this was done a couple of years before Astron came out with their BB option.   Nowadays it may be easier to just buy the BB version from Astron - but sometimes it's more fun (and more educational) to roll your own.

• Schematic of the RS‑12A‑BB     Factory Battery Back-Up Schematic donated by John Lund
• Schematic of the RS‑20A‑BB     Factory Battery Back-Up Schematic donated by Rick Williams N8EDR
• Schematic of the RM‑35A‑BB / RM‑35M‑BB     Factory Battery Back-Up Schematic donated by Larry Horlick VYØHL
  Note that the schematic title block says that it is for both the RM-35M-BB (rack mount, w/meters), and the RM-35A-BB (rack mount w/o meters), but the schematic does not show any metering components.   If you need metering look at the next one and copy that section.
  The metered version of this supply is also known as a Motorola RRDN6933A, which comes with lighted meters (the first that anyone that I know has seen with that feature).
• Schematic of the RS/RM‑50M‑BB     Factory Battery Back-Up Schematic donated by Robert Burton KD4YDC

Schematic Diagrams of Astron Linear Power Supplies

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 a 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 ID's 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 ID's... 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.

Notes:

• An "RS‑" prefix is a standard power supply. I suspect that RS stands for Regulated Supply.
• 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.
• SS‑ series are switching power supplies - their schematics are further down the page.
• SL‑ series - you'd think that the leading "S" would imply a switching supply, but these are low profile supplies. Really, they should have been RL‑. Also note that the SL series have different suffixes that indicate the make/model radio they were made to work with. Check the catalog pages on Astron's web site for all the details.
• A trailing "M" indicates the metering option. Newer supplies (possibly starting around 2008) have illuminated meters.
• A trailing "ML" indicates there's a cigarette lighter socket on the front.
• A trailing "S" is the speaker version.
• A trailing "BB" indicates the battery backup option. See the comments above on the battery backup feature.

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 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 SL11RRA is a 13.8V 11AMP 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 (click here for a photo).
A conversion list of Motorola to Astron model numbers can be found here.

Donations of additional schematics for the library below are always welcome !!
Send them to Mike WA6ILQ at: (callsign) -at- repeater-builder -dot- com - and thanks in advance!
(you will be credited unless you tell us to assign it to A. Nony Mous)

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.

• RM-60A, RM-60M   42 KB PDF, dated 08-16-1988 donated by Tom Allinson WB6DGN
  
• RM-60A, RM-60M   395 KB PDF, dated 08-16-1988 but dated on the lower left of the schematic 03/20/96   Donated by Mike Morris WA6ILQ
  
  The RM series has a 60 amp model, the RS series does not. At the moment this is the only RM-specific model in the library.
  
  
• 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 Morris WA6ILQ
  
  
• RS-10A, RS-10S   105 KB, dated 9-81   Donated by Bill Netzlof KL7IGB
  
  
• RS-10A, RS-10S   368 KB, dated 9-88 (but rubber stamped Sept 22 2003 on the drawing)   Donated by George Franklin WØAV
  
  
• RS-12A   199 KB, dated 11-83   Donated by Richard Reese WA8DBW
• RS-12A, RS-12M   125 KB, dated 6-88   A. Nony Mous found this on a Russian web site and forwarded it.
• RS-12A, RS-12M   42 KB PDF, dated 6-88   Donated by A. Nony Mous
• RS-12A-BB   119 KB, dated January 2000   donated by John Lund.   See the comments above on the battery backup feature.
• RS-12A, RS-12M   1.01 MB, dated 11-2009   donated by Greg Shaw N4GOS
  
  
• RS-20A   71 KB, dated 11-12-1978   Donated by Gary Eldridge KC8UD
• RS-20A, RS-20S   79 KB, dated 9-23-88   Donated by Kevin Custer W3KKC
• RS-20A, RS-20S   185 KB, dated 9-24-88   Donated by A. Nony Mous
• RS-20A-BB, RS-20M-BB   330 KB, dated 01-2000   Donated by Rick Williams N8EDR   See the comments above on the battery backup feature.
  
  
• RS-35A   135 KB, dated 1-11-1978   Donated by Joe McIntyre W4DEX
• RS-35M   46 KB, dated 4-87   Donated by Kevin Custer W3KKC
• RS-35A, RS-35M   216 KB, dated 4-87 but different   Donated by Mike Morris WA6ILQ
• RS-35M   47 KB, dated 4-87, 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   900 KB PDF, dated 5-91   Donated by Mike Morris WA6ILQ
• RS-35A, RS-35M   87 KB PDF, dated 5-95   Donated by Mike Morris WA6ILQ
• RS-35M   498 KB JPG, dated Jan-2000   Donated by A. Nony Mous
• RS-35M   75 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 illumination.
• RM-35A-BB   76 KB PDF, dated January 1993 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   182 KB, dated dated Jan-2000   Donated by Kevin Custer W3KKC
• RS-50A, RS-50M, RM-50A, RM-50M   44 KB PDF, dated 03-21-96 donated by Tom Allinson WB6DGN
• RS-50A-BB, RS-50M-BB   127 KB, dated 7-95   Donated by Robert Burton KD4YDC   See the comments above on the battery backup feature.
  
  
• RS-70A, RS-70M   87 KB, dated 4-87   Donated by Henry Clark KC4KZT
• RS-70A, RS-70M   73 KB, unreadable date (probably 8-88)   Donated by Mike Morris WA6ILQ
• RS-70A, RS-70M   227 KB, dated 6-97   Donated by Avent Lane
• RS-70A, RS-70M   69 KB PDF, dated January 2007 donated by Tom Allinson WB6DGN
  
  
• VS-20M   1.02 MB, dated 11-12-78   Donated by A. Nony Mous
• VS-20M   100 KB PDF, dated 9-86   Donated by A. Nony Mous
• VS-20M   74 KB PDF dated January 2000 donated by Larry Horlick VYØHL
  This supply is also known as a Motorola RRDN6082A. The Moto invoice says "VS-20ML".
  
  
• VS-35M   322 KB, dated 01-87   Donated by Steve Duncan, WA4ITA
• VS-35M   322 KB, dated 01-2000   Donated by Bill Neuman, WB9EFP
  
  
• VS-50M   25 KB PDF, dated 8-82   Donated by Bob Shields, KA9TYL
• VS-50M   70 KB PDF, dated 11-95   Donated by Tim Bovard, Senior Technician at Nichols & Simpson, Inc., Organbuilders in Little Rock, Arkansas.
  
  
• VS-70M   132 KB, dated 6-30-95   Donated by Brian Palmersheim KBØETC

Schematic Diagrams of Astron Switching Power Supplies

• SS-12 switching supply   55 KB,   Dated 8-22-1996   Donated by Eric Lemmon WB6FLY
  No parts values other than what Eric noted.
• SS-18 switching supply   351 KB,   Dated 11-03-1998   Donated by A. Nony Mous
• SS-30 switching supply   70 KB,   Dated 9-25-2000   Donated by Eric Lemmon WB6FLY
  There is minimal parts info on the schematic. Further info is available here.
• SS-30 switching supply   301 KB,   Dated 9-25-2000   Donated by A. Nony Mous
  A second copy of the same schematic, but a little more readable.
• 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.
• 1212-18 Switching Regulated Converter   140 KB,     Donated by Tom Allinson WB6DGN
  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 unit.
• 2412 Switching Regulated Converter   140 KB,     Donated by Ed Lambert K1ZOK
  This unit allows you to use a +12v device (like a two-way radio) on a +24 volt battery system (like in many Kenworth, Peterbilt and other large trucks, for example, fire trucks). The negative side is common.

Schematic Diagrams of some other popular Astron Linear Power Supplies

• SL-11A low profile supply   95 KB PDF   Dated 4-15-1990
• SL-11A/11R low profile supply   172 KB   Dated Nov 2009   Donated by Paul Mandel W4PGM
• SL-15 low profile supply   135 KB PDF   Dated 4-15-1990   Donated by Ed Lambert K1ZOK
• SL-15R low profile supply   184 KB   Dated Nov 2009   Donated by Dave Christensen KD7UM
• LS-25A 28 Volt, 25A intermittent, 18A continuous, linear power supply   35 KB PDF   Dated 4-16-2004   Donated by Astron.
  A no-frills 28V power supply similar to the RS-70 supply except for the output voltage.
• VLS-35M 28 Volt, 35A intermittent, 25A continuous, linear power supply   53 KB PDF, dated June 1995   Donated by Ron Vincent KF4D
  Similar to the VS-70M supply except for the output voltage (variable from 5v to 32 v).

Back to the top of the page
Back to Home