|On the plus side this is probably better than some no-name Chinese versions and it's a linear supply and hence produces much less RFI than a switching supply (especially most Chinese switching supplies). It also has an adjustable output voltage if you take the cover off and carefully snake a screwdriver deep into the circuitry.|
On the minus side it's a very marginal design and Astron cut a lot of corners. There are two big TO-3 metal transistors mounted on the back and they're uncovered with roughly 24 volts DC on them. Further there are potentially arc welding levels of peak current available. So if a coax connector, wire, bracket, 3.5mm plug, USB cable, etc. contacts one of them be prepared for some fireworks, possible molten metal, and potentially damaged equipment. Even a sweaty finger might be in for a very unpleasant surprise. It's a safety hazard and could damage the power supply and even more likely other equipment such as sending 24 volts at dozens of amps into your PC's USB port likely frying the motherboard of your PC or laptop.
The main filter cap is rated at 25 volts and on my AC line voltage idles at 24.5 volts across the cap which is cutting it way too close. A 35 volt cap might have cost 50 cents more but Astron was more interested in maximizing their profits by shaving every penny out of the design.
This fanless power supply runs unusually warm even at very light loads. It's uses a cheap likely Chinese sourced low profile E-lam power transformer that runs warm with no load as it likely has too little low quality iron in it and lots of inherent hysteresis loss. It also has to drop from 24.5 volts unregulated to 13.8 or whatever you have it set at meaning there's a rather massive loss as heat at even very modest output currents. For example with even just a 2 amp load this thing has to dissipate nearly 20 watts of added heat on top of its already excessive unloaded losses.
A better quality linear supply would use a beefier transformer, more filter capacitance, and lower drop MOSFET pass transistors, so it could run a much lower unregulated voltage with less ripple limiting the voltage drop across the output transistors and hence the heat produced. But Astron clearly would rather shave every penny out of the bill of materials and let this thing cook itself to death.
There's no inrush current limiting and if you flip the power on and happen to catch the AC line waveform near the peak it lets out a nasty magnetic grunt from the massive inrush spike. Not surprisingly just after a year the cheap little under rated power switch in mine welded itself on because of this cost cutting design flaw.
There's a little tiny under-rated MOV on the line side to provide some transient protection but it's BEFORE the power switch so it's across the AC line 24/7 which is really poor engineering. MOVs gradually become ineffective and this one will be rendered useless much sooner than it would have on the other side of the power switch. One wonders if they even have any competent engineers at Astron?
If you do some digging on the web you'll find several posts about people who significantly modify even their brand new Astron power supplies to overcome at least some of their unfortunate design flaws and cost cutting. It's sad as they're not exactly cheap to buy even if they're very cheap for Astron to make.
Sadly there are not many similarly priced options besides lower priced Chinese junk that's even worse. Tripp-Lite and MFJ make some linear supplies but I suspect they're re-badged Chinese units with similar issues. You can get "open frame" much higher quality linear supplies from real power supply companies like Bel Power, SL Power, PowerOne, etc. for not too much more but they're not really designed for desktop use. Finally you can get lab-grade test bench linear power supplies that are WAY better engineered but also much more expensive.
In summary it's really unfortunate Astron cuts so many corners but I don't have any better suggestions for a similarly slim quiet desktop supply around the same price. If you buy an Astron SL-11R, or any other model with exposed transistors, I'd suggest covering them with some tape as Astron was too cheap to include the $0.15 plastic covers to prevent you arc welding things to them.