Switcher vs Linear Power Supplies - K6UDA Radio Episode 35

Is your big boat anchor of a power supply necessarily better than a new small switching power supply? This time I'll look at both and compare a couple of the leading switching units. Get ready for a QSO party from the Florida Everglades & could this be the week we hit 5,000?

 

sub'd! I look forward to the contest when the time comes.

 

I think the switching power supply is much better than the low frequency ones. First of all the switching supply's don't need
much filtering. Drawing 20 AMPs from mine and it don't even groan. Barely gets warm. They can develop a lot of current in a hurry. They can stand a dead short without being destroyed. Guess why I know? That was shorted on power up. I don't know what would happen when the output would short when it was already running.

 

My Astron RS-35M rules in the ham shack. It's ultimately quiet in every respect... no RFI or fan noise. What more could one ask?

My 2005 Astron SS-30M works fine, but does generate some ripple and or RFI that's noticed on my HF radios at my Alaskan QTH. It's a great portable supply.

If I lived in most Lower-48 locations where band noises are higher, I could likely stand a switching power supply. If one lives in an RF quiet location, stick with an analog supply.

 

I have used both a RS-35 and RS-50 for years. Built like tanks, simple as tree stumps and easy to fix (haven't had to fix either one yet). To paraphrase the old expression about children, "power supplies should be seen and not heard."

The RS-50 keeps my feet warm when chasing late-night DX on cold evenings, too. What's not to like?

 

I'd just like to note that I love my Powerwerx 30A PSU and it doesn't make a sound!

 

Transcript for us folks that have no media players??
I can not view youtube type stuff on the radio computer, the sound card is for doing rtty, psk31 etc, and no speakers.

 

Talk more about ham radio, and less about selling ham radio out. Banana plugs rock, and Anderson poles suck.

 

Hmmmm. Maybe this should be more about build quality than power supply type.

I have two PowerWerx SPS-30DM supplies, with adjustable output and digital AMP/VOLT readouts. These are 25 AMP supplies (according to the label on their bottom), not 30A. Picked one up at a hamfest for $100, paid more for the other. Both work great and are very small and light - easy to travel with. I can manage to heat them up a bit running high duty-cycle modes, but have never had one quit. I've not done too much on 80M and 160M until recently, so have not had a chance to check those supplies for interference on those bands (there are reports of fignificant RF hash on 80M). On 40M and up, they seem fine. I do not know if these supplies have significant overvoltage protection. No mention of it in the sparse manual or on-line and never had opportunity to test this.

Likewise I have four Astron linear supplies: RS-35A (25A continuous), RS-35M (25A continuous), RS-20A (16A continuous), VS-50M (37A continuous), of varying ages (some 20+ years old). They are RF quiet, period, but some are fairly noisy in terms of audible hum from transformer laminations. All of them are large and HEAVY. Two have had failures - one intermittent and one complete. The intermittent failure was caused by the + and - binding posts rotating in their mounts and shorting internally. Astron does not use a positive locking system for these posts and spaces the internal wiring quite close together, so a little rotation and ZAP! Lucky the supply had good overvoltage/overcurrent protection, so no permanent harm done. If you buy a used Astron linear supply - check for this before you use it - this problem happens a lot. The other supply had its one large cap go leaky above 12V - an odd failure mode - it acted almost like a Zener diode. Upon replacement, I found the OEM cap was rated within a couple of volts of the supply transformer output - very little margin - not good. I replaced it with a cap having about 100% margin, and no further problems. The good news is that the circuitry in the Astrons is so simple and well documented they are easy to diagnose and fix. BTW - the Astron RS-35A gets quite warm when driving my FTDX-3000 on high duty cycle modes (about 22-24A) - DO NOT touch the transistors when doing this - HOT! HOT! HOT. For the most part, internal wiring and component quality is good - just wish they put ore margin into the main caps.

A close friend and Ham purchased both the PowerWerx SPS-30DM and the less expensive MFJ-4230MV. Both look very similar from the outside, with the exception that the MFJ unit has an analog meter and the PowerWerx has a digital one. The MFJ unit failed completely after just one year (just days outside of warranty period). MFJ refused to repair the supply under warranty. So my buddy took his apart - and for good measure, opened up the PowerWerx supply as well to compare them on the bench. His conclusions were that both supplies used similar or exactly the same circuitry/housing, etc (with minor differences, like metering), and likely came from the same Chinese manufacturer, but off of different quality production lines. The MFJ supply had very poor solder joints, though, and after touching them up and clearing an apparent solder bridge, it came back to life. The PowerWerks unit had very good soldering and finish quality. Note that uneven solder and finish quality can cause RF hash production to vary from unit to unit as well as critical failures in units - some of which could cause overvoltage conditions, some of which have been reported in the MFJ switching supplies (). My friends conclusions: Pay the extra for the better assembly work of the PowerWerx unit.

CONCLUSIONS: If you are looking for a reliable, easy to maintain and RF quiet fixed station power supply, and don't mind some audible hum, get the Astron linear supplies. They are a long-time "gold standard" for AC to 13.8 VDC power conversion, not because they're perfect, but rather because they are a well understood product (lots of on-line schematics and repair pointers), with consistent quality, are easy to repair (no exotic circuitry or magnetics), produce zero RF hash and are impractical to steal (in most cases) because they weigh a ton. And they have proven, reliable overvoltage protection (regulation and a crowbar circuit). If you are short on space, rarely work 80M and like to travel with a Rig and power supply, get the PowerWerx SPS-30DM or similar, and avoid the cheaper versions of the same. Consider - Elecraft sells and recommends the PowerWerx SS-30DV to power their radios. Hard to get a better endorsement.

Brian - K6BRN

 

Great Topic and Video Bob!

I personally like and will only use Astron Linear Power Supplies: They Last 30 Plus years, they are quieter to the ear and on the scope, and if they did need repairing; most amateurs could repair them or ask a fellow Ham to help in the repair.

I've been a technician at a company in the Vancouver BC area for 22 years now and we started to use Switcher power supplies in our products about 10 years ago. Long story short; I've seen them DOA new out of the box and units returned between 1 and 7 years due to a switcher PS that died. We have not had one single Linear PS failure in the 22 years I've been at the company.

If you have the room, the power supply is going to be used in your home only, and you want to buy 1 power supply to last a lifetime go Astron Linear!

73 and Merry Christmas from the Great White North !
Lawrence (VA7LTX)

 

Great Report, Input, and Fault Finding Brian!
73 and Merry Chistmas
Lawrence

 

A couple of things which I feel make the old linear PS worthwhile:
1. Voltage regulation...how likely is it to have transient response damage or shut down your transceiver?
2. Failure modes.....how likely is it to have a failure mode damage your transceiver?

No doubt that the smaller weight and size are nice attributes for the switcher.

 

1. The same as any PS that operates in a "closed loop". Switchers have come a long way since the early days decades ago.
2. The same as any PS that operates in a "closed loop". Switchers have come a long way since the early days decades ago.

 

If he does the transcript, he won't get Youtube hits, which help keep the show going. FYI.

 

My 1 year old RS-35 was a piece of crap.

First the transformer smoked, replaced it and the supply still didn't work.

Further checking revealed the parallel bridges were bad. Replaced them and it still didn't work.

Further checking the regulator chip and found it bad. Replaced it and it still didn't work.

Gave up and gave it away for parts. Will never buy another Astron supply, they never offered any help (because it was just over a year warranty) and only offered either they repair it or sell parts.