The basic idea of a linear power supply is to rectify AC into DC to charge a big capacitor at around twenty-five volts or so, with a fair bit of ripple at 120Hz. Either way, it’s enough to comfortably keep a typical 100W transceiver going indefinitely, with capacity to spare. The RS-35A has a continuous duty rating of 25 Amps according to the catalog, or 27 amps according to the data plate on the bottom of my unit. If you buy a supply that has a continuous duty rating sufficient to supply the maximum power you’ll ever draw from it, you won’t have to worry about overheating during long transmissions, and your supply will run cooler and last longer. The Astron Catalog includes each model’s continuous duty rating. However, this is an “ICS” rating, for intermittent duty only.
For example, the RS-35A can deliver up to 35 amps at 13.8VDC.
If you want to add meters, DC power outlets, whatever, there’s plenty of space behind the front panel, on the right side of this photoĪ few words about ratings: The Astron model numbers include their peak current rating. Again, nothing here that would obviously cause a problem, especially if the unit isn’t subject to a lot of vibration, but it’s not exactly pretty, either. Since each package is rated at 35A, which is the peak rating of the supply, then it ought to work regardless, but there isn’t nearly as much margin as one would first guess if you thought that putting in two rectifier packages would double the current capacity.Īlso notice that, embedded in the white heat sink compound on the left, there appears to be a short piece of metal that had been trimmed off of one of those rods that is used to connect the parallel rectifiers. This can cause the warmer diode to get still warmer, and conduct more, and spiral into a situation called “current hogging”, where one diode gets hot and takes most of the current and the other one loafs along and stays cool. When you place diodes in parallel, if one gets slightly warmer than the other, the warmer diode will conduct more than its cooler neighbor. However, no measures have been taken to ensure that the load is shared equally between the two rectifier packages. The RS-35A is rated at 35A (peak), and uses two bridge rectifiers, each rated at 35A, placed in parallel to share the load. Red wire goes to + side of filter capacitor. Yellow wires are from transformer secondary.
Let’s take a look around the Astron RS-35A. This noise can be suppressed, sometimes quite effectively, but nothing is quieter than a good linear supply. However, switching power supplies generate electrical noise which can interfere with radio operation. These days, switching power supplies are available which are much smaller, more lightweight, and often significantly more efficient. The basic design is very old, simple, well-proven, rugged and easy to service. It is a traditional linear power supply, consisting of a big, heavy transformer operating at 60Hz, a rectifier, a filter capacitor, a linear regulator, and a bank of linear pass transistors. This model has been in continuous production for decades. I recently purchased the venerable Astron RS-35A, one of the most popular amateur radio power supplies. It also allows a radio to operate easily off of 12V lead-acid batteries, or automotive electrical systems. Keeping the power supply in a separate unit from the radio makes the radio lighter and cheaper, and allows the heat from the power supply to stay far away from the radio. In home stations, this is usually supplied from the AC mains power via a “power supply”. Most ham radio transceivers do not run directly off of mains AC power, but instead operate from about 13.8VDC, using something in the range of ten to thirty amps or so.
#Astron ss 25 service manual portable#
All of these supplies provide a well-filtered 13.8 Vdc output for the operation of mobile or portable equipment from your 120/220 volt wall current.The Astron RS-35A, with the classic Altoids tin to show scale. Their low-profile design and light weight make them perfect for portability or desktop use.
Built to exhibit RFI immunity, these power supplies include an EMI filter and are even RFI resistant in the HF bands!
#Astron ss 25 service manual series#
While all of them make excellent general purpose power supplies, many of the SS Series supplies are designated to work with, and provide enclosures for, specific land mobile radios.ĭelivering output from 7 to 40 continuous amps, depending on the model, these Astron supplies are manufactured with robust components for durability and long life. SS-18 18A Peak / 15A Continuous Switching Power SupplyĪstron Corporation SS Series Switching Power Supplies are highly regulated and designed for moderate to high power applications.