Astron rs 20a ремонт
Note: there is an Astron Wireless Technologies company that makes some very nice antennas. It is a totally separate operation with no connections to the Astron Corporation that makes power supplies.
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.
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.
 | 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 OVPR-12V donated by Joe Orrico WB6HRO (52 kB PDF) Astron’s documentation shows an extra LED indicator, which is not actually part of the OVPR-12V. |
| | A photo of Astron’s OVPR-12V board (found on the web). |
Repair and Operation Articles:
| | 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. |
| | 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 design. |
| | Troubleshooting Astron Linear Supplies by Jim Ussailis W1EQO (630 kB PDF) From the Yankee Clipper Contest Club’s «Scuttlebutt» newsletter Issue 232, August 2015. |
| | 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. |
| | Refreshing / Maintaining Astron Linear Supplies by Robert W. Meister WA1MIK Common maintenance things you can do to keep your Astron supply running for many years to come. |
| | Crowbar SCRs in Astron 13.8V Linear Supplies by Robert W. Meister WA1MIK A summary of SCRs used by Astron and some available replacements. |
| | Main Capacitors and AC Line Fuses in Astron 13.8V Linear Supplies by Robert W. Meister WA1MIK A summary of main filter capacitors and AC line fuses found in Astron supplies. |
| | LM723 Regulator Operation by Robert W. Meister WA1MIK A short explanation of what’s going on inside the regulator IC in an Astron power supply. |
| | 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. |
| | Adjusting the Output Voltage of Astron Linear Supplies by Robert W. Meister WA1MIK So easy, a visually handicapped (blind) person can do it! |
| | 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. |
 | If your linear power supply regulator board is beyond repair, you can buy a brand new one from Astron for $25US 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 (visible in the component side photo above and labeled «R5» on the solder side photo above) adjusts the power supply’s maximum output voltage, typically from 11 to 15 volts (22 to 32 volts on LS and VLS power supplies). See the article above for a more detailed procedure. |
| | Stu K2QDE reports «I recently learned that very light to unreadable front panel silk-screening existed in a number of production Astron power supplies around the time I purchased mine in mid 2017. I searched for vendors that could make a new stick-on label. I sent along a laser printout of an SS-55M front panel as a sample. These are plastic, self-adhesive strips, slightly larger and brighter than factory silk-screening. The Astron logo is slightly sharper than the silk-screened version. Perfect when refurbishing your Astron supply. Click here to see a photo. Contact sonia [ at ] kellylaserworks [ dot ] com for more information. |
| | Astron is now selling many of the more common parts for their power supplies, such as the power switch, meters, illumination kits, pass transistors, bridge rectifiers, and the crowbar SCR. Check their newly designed web site for pricing and availability. |
| | Astron Linear Supply Battery Backup Modifications All the schematics and modifications necessary to add a battery backup to your Astron linear power supply. Astron makes a stand-alone battery backup module that automatically switches to the battery source upon power failure. It also charges the battery and works with 12 and 24V systems. The BB-30M specs, hookup info, and schematic can be found here as a 350 kB PDF file. |
| | 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. |
| | Replacing Astron Meter Lamps by Larry Lockard N7FM (offsite 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. |
| | Upgrading the Astron Over-Voltage Crowbar Circuit by Rich Post KB8TAD (offsite link) Repairing a supply, analysis of key circuits, and replacing the SCR crowbar with MOSFETs. Very well written and chock-full of troubleshooting information. |
| | Fixing False Tripping of the Crowbar Circuit by Ray Maynard NØLGR Ray figured out why some of his supplies were falsely triggering the SCR and modified the supply to stop this from happening. |
| | 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. |
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.
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 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.
Variable output supplies are identical to the non-variable supplies except for the two front panel adjustment controls. Similarly, supplies with meters are identical to those that don’t have meters except for the meters, calibration pots, and possibly a DPDT switch used on supplies that have just one meter for amps and volts. So while you may not find an exact schematic for your particular unit, if you find one for a variable or metered supply, use that one.
Supplies rated for 12A or less (SL-11 or RS-12 and under) usually have two 4mm, 15A, 3-way binding posts on the rear for output terminals. The Cliff Electronic Components TP1 (available from Newark.com and other suppliers) seems to be the ones that will fit the 1/4 inch holes with keyways. Supplies rated for higher current usually have 1/4-20 threaded stainless steel hex bolts with flat washers, split lockwashers, and hex nuts for output terminals. Both are insulated from the chassis with fiber shoulder washers (Keystone 4711) that fit into 5/16 inch holes. Some of the Slim-Line (SL) supplies have a cable and connector appropriate for the radio that it would normally power.
Notes about Serial Numbers:
The year of manufacture is the first two digits, the month is the next two digits, and the remaining digits are a sequential number that’s assigned to each unit. We’re not sure if it’s model-specific or the total number of all units made that month by Astron. This date code information has been confirmed by Astron.
Notes about Model Numbers:
The model number is constructed from a prefix (letters), a peak current value (digits), and a suffix (letters). Look for a schematic based on the current value first. The circuitry is similar for the different prefixes and suffixes. For example, the Variable power supplies with front panel controls just add two pots. Any supply could have meters added, if they’ll fit on the front panel. These don’t affect the basic circuitry.
Prefixes:
- An «RS-» prefix is a standard desk-top 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. See the article elsewhere on this page.
- SL- series are Slim-Line or Small Linear power supplies. Their schematics are further down the page. These are often found inside a larger enclosure that has room for a two-way radio to be mounted above the supply. They are also found in some small desktop repeaters that use a pair of mobile radios. The SL series suffix characters indicate the peak current capacity and/or the make and model of the radio that fits the enclosure. Check the catalog pages on Astron’s web site for more details.
- LS- and VLS- series are Linear Special-voltage and Variable Linear Special-voltage power supplies, usually 28 volt.
- LSRM- and VLSRM- series are identical to the LS- and VLS- supplies except are Rack-Mount.
- SS- series are Small Switching power supplies. Their schematics are further down the page.
- SRM- series are SS switching power supplies in a Rack Mount configuration.
- SLS- are Switching Special-voltage power supplies, usually 28 volt.
- SLSRM- are Switching Special-voltage power supplies, usually 28 volt, in a Rack Mount configuration.
Suffixes:
- A trailing «A» seems to be the default if there’s no other suffix. Some supplies have this, some don’t.
- A trailing «R» seems to be used for power supplies that were sold with an enclosure that could accept a mobile radio, usually only found on the SL-series.
- 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 (SS) usually have two meters.
- A trailing «L» indicates there’s a cigarette Lighter socket on the front.
- A trailing «S» indicates 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 «AP» indicates a pair of Anderson PowerPole connectors on the front panel. These seem to be available (so far) on a few select fixed-voltage desktop models: RS-20M, RS-35A, and RS-35M.
- 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 SL-15M variant. Astron also builds custom supplies for GE, Icom, E.F. Johnson, Kenwood, Motorola, Uniden and Vertex. For example, the Astron SL-11RRA is a 13.8 Volt 11 Amp unit specifically designed with a metal sleeve built 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 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 these transistors, so they get much hotter. Current foldback may also occur earlier at these lower voltage 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 300 kB, dated 12-1989 donated by Oscar Ramsey NV3G The RS-5A is most likely the same. The regulator board in a 2010 RS-5A supply seems to be used in the 3A, 4A, 5A, and 7A supplies, however there are no crowbar components installed in the 3A, 4A, and 5A supplies. (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 10-1994 donated by Mike Morris WA6ILQ |
| | RS-10A, RS-10S 105 kB, dated 09-1981 donated by Bill Netzlof KL7IGB |
| | RS-10A, RS-10S 368 kB, dated 09-1988 donated by George Franklin WØAV |
| | RS-12A 199 kB, dated 11-1983 donated by Richard Reese WA8DBW |
| | RS-12A, RS-12M 127 kB, dated 06-1988 |
| | RS-12A, RS-12M 31 kB PDF, dated 06-1988 |
| | 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 71 kB PDF, dated 11-2009 donated by Greg Shaw N4GOS |
| | RS-20A 71 kB, dated 11-1978 donated by Gary Eldridge KC8UD |
| | RS-20A, RS-20S 79 kB, dated 09-1988 donated by Kevin Custer W3KKC |
| | RS-20A, RS-20S 185 kB, dated 09-1988 |
| | RS-20A 44 kB PDF, dated 01-2000 donated by Ron N8HXR |
| | RS-20M 117 kB PDF, dated 01-2000 donated by Ron N8HXR |
| | RS-20A-BB 330 kB, dated 01-2000 donated by Rick Williams N8EDR See the comments above on the battery backup feature. |
| | VS-20M 26 kB PDF, dated 11-1978 |
| | VS-20M 80 kB PDF, dated 09-1986 |
| | 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 01-1978 donated by Joe McIntyre W4DEX |
| | RS-35M 46 kB, dated 04-1987 donated by Kevin Custer W3KKC |
| | RS-35A, RS-35M 216 kB, dated 04-1987 but different. Donated by Mike Morris WA6ILQ |
| | RS-35M 47 kB, dated 04-1987, 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 09-1988 donated by Jim Bacher WB8VSU |
| | RS-35A, RS-35M 159 kB PDF, dated 05-1991 donated by Mike Morris WA6ILQ |
| | RS-35A, RS-35M 46 kB PDF, dated 05-1995 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 illumination. |
| | RS-35M 127 kB PDF, dated 02-2017, drawn by Larry Joy WN8P This is an actual as-built schematic, drawn from scratch to current IEEE specifications, of an older (1978) RS-35M 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). Astron has since added some parts to the design; these are NOT reflected in this schematic or the parts list below. 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 01-1987 donated by Steve Duncan, WA4ITA |
| | VS-35M 262 kB PDF, dated 01-2000 |
| | RM-35A, RM-35M 33 kB PDF, dated 01-2013 donated by John D’Errico, N1ERF |
| | RM-35A-BB 80 kB PDF, dated 01-1993 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. |
| | RM-35A-BB 300 kB PDF, created 10-2020 by N. Eric Jorgensen W1NEJ This is a factory Battery Back-Up supply purchased in October 2020. Eric reports:
|
| | 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 03-1996 donated by Tom Allinson WB6DGN |
| | RS-50A, RS-50M, RM-50A, RM-50M 154 kB PDF, dated 01-2013 donated by David Bent |
| | VS-50M 25 kB PDF, dated 08-1982 donated by Bob Shields KA9TYL |
| | VS-50M 74 kB PDF, dated 11-1995 donated by Tim Bovard |
| | RS-50A-BB, RS-50M-BB 127 kB, dated 07-1995 donated by Robert Burton KD4YDC See the comments above on the battery backup feature. |
| | 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 08-1988 donated by Tom Allinson WB6DGN |
| | RS-70A, RS-70M 73 kB, unreadable date (probably 08-1988) donated by Mike Morris WA6ILQ |
| | RS-70A, RS-70M 227 kB, dated 06-1997 donated by Avent Lane |
| | RS-70A, RS-70M 74 kB PDF, dated 01-2007 donated by Tom Allinson WB6DGN |
| | VS-70M 54 kB PDF, dated 06-1995 donated by Matt Trull KX4GG |
Slim-Line (Low-Profile) Linear Power Supply Schematics:
| | SL-11A 99 kB PDF, dated 04-1990 |
| | SL-11A, SL-11R 172 kB, dated 11-2009 donated by Paul Mandel W4PGM |
| | SL-15A 120 kB PDF, dated 04-1990 donated by Ed Lambert K1ZOK |
| | SL-15M 42 kB PDF, dated 12-1998 This is also the Motorola HPN9041 that is found in the GR400 X-Pand and GR1225 Repeaters. It can be used with an HLN9455 Battery Revert accessory. |
| | 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, in a rack-mount configuration (LSRM-25A), is also sold under the Uniden name as their model ARX 330. |
| | LS-35M 28 Volt, 35A intermittent, 25A continuous, linear power supply 197 kB, dated 07-1993 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 Vincent KF4D Similar to the VS-70M supply except for the output voltage (variable from 5 to 32 Volts) and current. |
| | VLS-35M 28 Volt, 35A intermittent, 25A continuous, linear power supply 321 kB PDF, dated 04-2016 donated by David Bent |
Switching Power Supply Schematics:
| | SS-10 4 MB PDF, early 1990s Schematic plus parts list for SS-10, SS-12, SS-18. |
| | SS-12 42 kB PDF, dated 08-1996 donated by Eric Lemmon WB6FLY No parts values other than what Eric noted. |
| | SS-18 47 kB PDF, dated 11-1998 |
| | SS-25M, SS-30M 483 kB PDF, dated 09-2000 Shows meters and the 120V/240V input power selection switch. |
| | SS-25M, SS-30M 1.8 MB PDF, dated 09-2000 Schematic plus parts list. |
| | SS-25M, SS-30M 1.7 MB PDF, dated 11-2010 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 Lemmon WB6FLY There is minimal parts info on the schematic. Further info is available here. |
| | 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 1.1 MB PDF, dated 09-2000 donated by Alan Sewell N5NA Alan had to repair a couple 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. It does seem that a meter calibration pot is missing from the ammeter circuit in the schematic, but since he left no contact info, this will have to go uncorrected until he sees it. Read his full story here. A local copy can be found here. |
| | 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 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 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. |
| | 2412-12 320 kB PDF donated by Tom KN4ONE This unit allows you to use +12v devices (like two-way radios) on +24 volt battery systems. This one uses a TL494 switch-mode regulator IC to do the work. |
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
Dozens of people contributed information to this web page, some of whom are no longer with us. The list became too long to manage. Several contributions were sent in anonymously or the person asked not to be identified with a particular submission. We are grateful to all those who took the time to send us information.
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.
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