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Reviews Categories | Power Supplies | MEGA-WATT S-400-12 Help

Reviews Summary for MEGA-WATT S-400-12
MEGA-WATT S-400-12 Reviews: 25 Average rating: 4.1/5 MSRP: $65.00 + 5.00 SHIPPING
Product is in production.
More info: http://EBAY SELLER ELECTRONICS_5000
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AD0AR Rating: 4/5 Jul 10, 2015 22:49 Send this review to a friend
Inexpensive and works with minor flaw  Time owned: more than 12 months
First of all, everyone wants to save a buck on a basic thing such as a high current power supply which we all know can be very expensive. Our radios are expensive enough, why add insult to injury?? Well a linear supply is surely the least RF noise generating, but if that series pass transistor(s) electrically fails and shorts on a linear supply, our radios are instantly TOAST and more $$$ lost.
With switching supplies, the conveyed power is rectified AC from a high frequency electronically regulated oscillator , so it is highly unlikely to produce a over voltage condition from the electrical failure and shorting of the switching transistor. Most likely the AC mains fuse in the supply will blow, and the supply will need to be serviced and your precious radio will be safe being it is on the other side of a transformer which cannot convey a dc short. It is rare, but a over voltage condition can occur when the feedback loop on a switching supply opens, and then high voltage can be passed to the radio equipment.
Anyway these switcher type of supplies are much more energy efficient that the linear dinosaur counterparts that had huge heat sinks for the series pass transistors.
The major caveat of these power supplies is that the switching element can generate insurmountable broadband RF noise/hash.
After using three(3) of these MEGA-WATT S-400-12 for over two years, I have encountered only one supply that had an electrical anomaly- the DC+ was tied to the chassis case/AC ground.
After disassembling the faulty supply (lots of rf hash) and removing a tiny solder splash that shorted the ac/chassis ground to the + DC output, all was good.
Filtering is pretty rock solid and I could not notice any noise/hash when properly wired and using a separate dedicated ground for the radio.
Do not make the newbie mistake of tying the DC output ground (-) to the chassis of the power supply! No damage may result, but the conducted RFI can wipe out all HF and possibly some VHF ham bands.
To be RFI safe, I still used a large 2" 31 mix toroid on the DC output leads wrapped for common mode suppression but this is probably overkill with 14 turns on each side. I noticed no 80/160M changes to ambient RX conditions with or without this addition.
The power supplies have all performed admirably with my only nitpick is the cheap Chinese cooling fan. They all have failed with the wailing agony we are all too familiar with when a computer fan fails. I ended up not replacing the OEM fans as they were loud and annoying, but redrilled a few holes, added a 10 ohm resistor in series with a new 8cm fan and mounted the fans on the of the power supply with appropriately mounted finger saving fan guards covering all pertinent moving parts. The 10 ohm resistor slowed the fan down to unnoticeable audio levels while still keeping the supply cool to the touch, even running 100 watts of RTTY into my dummy load for a sustained 10 minute test.
These supplies are a best bargain in my book, even if they may need a fan mod which I am sure all of you amateurs could do with one hand behind your back. After all you guys did pass a basic electronics portion of the ham exam (I hope) ;-) Perfect for any project needing high current in a very small form factor.
Good luck, God Bless, In got we trust, all others we monitor de AD0AR
KD9WXB Rating: 5/5 Aug 22, 2014 21:39 Send this review to a friend
Sill Going Strong  Time owned: more than 12 months
I have had this running for a year now and its awesome. I just thought I would check back in and report. Definitely well worth what I paid for it.
KA7NIQ Rating: 2/5 Jul 6, 2013 07:58 Send this review to a friend
Full Of Birdies!   Time owned: 6 to 12 months
This little POS works great, where it works!
The 17 meter band is nearly unusable on my Kenwood TS 850, and I can find birdies on nearly every band.
The birdies on 17 meters are nearly S5 to S7, making weak signals unreadable.
LOL, I have to work between the birdies!
The Birdies are much much lower in amplitude, on the other bands, but they are still there.

I can not recommend this power supply, if you work 17 meters.
Other then that, I can live with this thing.
It runs the TS 850 to full power easily, and has never been turned off in the 6 + months I have owned it.

KK4RHF Rating: 4/5 Jun 3, 2013 20:56 Send this review to a friend
Would I buy more of these in the future? Absolutely!   Time owned: 6 to 12 months
The following is my personal experience with them.

I called Megawatt Power supplies on Tuesday and complained that regulation of the power supply that I bought in June of 2012 was getting unstable under load. (400-Watt model) We discussed the issue and decided I needed a new power supply plus an additional new one and a diode isolator. (These power supplies are smaller than a carton of cigarettes.)

The diode isolator couples the two supplies together, but they remain independent and utilize their own regulation circuits. According to the directions you must adjust the Voltage to within .1 volts of each other, it is easy to do if you have a light touch. I utilized a 300-watt dc load and adjusted one then the other. The unit under test was the only power supply running while adjusting the regulator to 13.8 volts. The prices are better than you would expect for technology these contain. The diode isolator cost less than what you could build one for. The heat sink is included and the circuits are potted in an epoxy compound. These come with the power cord and an inline rocker power switch. The new power supply and the isolator cost $105.00 U.S. Dollars shipping included.

It is Thursday and I have all of my new gear in hand. The supply that failed had a two-year warranty and they honored it without question. That, is how customer service is done to keep your customers happy. The power supply I sent back may not have been defective; it is possible that the RF power amplifier I was working on may
have been influencing the regulator circuit. Further investigation has proven to me that the power supply was not at fault. Checking all of my RF cables I found one that has a intermittent shield/ground. I repaired that before any other processes and testing began.

The new systems are hooked up functioning flawlessly. I have continued working on the same system I was working on when the other supply started drifting. So far they are rock solid and neither power supply is drifting and I now have extra available DC power when I need it.

Would I buy more of these in the future? Absolutely
KF7VXA Rating: 3/5 Jan 10, 2013 13:10 Send this review to a friend
Follow Up on 2 Defective Power Supplies  Time owned: 6 to 12 months
The 2nd power supply that stopped working started working again as long as the top is not screwed down tight. I will need to look and see what the top is touching, but the supply is now working again as long as I leave the top on loose. If I screw it down as it should be, the power supply is dead, go figure.
I guess all in all, for the price, these offer quite a lot of amperage and the voltage stays rock steady.
I may not be happy about the problem, but I'm sure I can fix it and will have a good working power supply again.
Having 2 power supplies is always a very good idea, a back up is a must.
KD0RMM Rating: 4/5 Aug 6, 2012 21:19 Send this review to a friend
Good supply, but has flaw  Time owned: 3 to 6 months
I have been using this supply with my IC-7000 as a base for 4 months now. It has powered the station **Perfectly** but I had noticed on the 75-80 meter band there has been a rather consistent noise floor issue of about S5 which the problem goes away when I switch to a 12 volt battery.
The other day I was rewiring my AH-4 remote antenna tuner when I saw a spark as I soldered a ground lug to the ground wire that was attached to the grounding terminal of the tuner. Nothing was turned on but the power supply so where was this phantom power coming from that my grounded soldering iron shorted out? I took everything offline and measured resistances and found that the chassis of this power supply is indeed tied to the +12V line along with the screw lug labelled with the AC ground symbol. (ground loop incurred through the AC ground lead of the power supply)
To resolve this issue, I mounted the power supply in an all enveloping plastic electrically insulating enclosure, removed the ac ground wire from the ground terminal and tied it to the DC ground on the power supply. Then I took a 250uf low ESR electrolytic, put the + side to the ac ground screw and tied the - to one of the dc ground screws as to make sure that any RF present on the chassis will have a definite low impedance to ground. Result? Dead quiet on 75-80 meters and **at least** 3 S units lower noise on all other bands!!!
I'm really surprised no one else has noticed this issue. Maybe my power supply was incorrectly fabricated? Anyway, I didn't have to void any warranties to fix the issue and now I get SUPER performance on the lower bands!
Another observation- Power factor on this power supply rolls in right around .65-.7 which equates it could be much better. I'm going to throw a brute force inductor in series with the ac supply to see if this addition could bring the power factor up closer to a .9
AD0AR Peter Dyrke (upgraded to my Extra)
KG4FET Rating: 4/5 May 11, 2012 08:13 Send this review to a friend
Great Value  Time owned: 6 to 12 months
After 6 mo of use I have found this little power supply to be very nice. I kept an accurate Volt meter on it for the first couple months and saw less then a half volt drop under load. I could find no birdies generated on HF-2M from the Power supply. Handles my FT450AT at 100 watts FM with additional load of an auto tuner, and a couple of low current meters with no issues.

It's small size and flexible mounting make it a great power supply for a go bag/box. The "test power cord" is adequate with a inline rocker switch but a heavier cord would be better. Add a fuse on the ac lines would be good as there is no protection for surges/shorts. I don't have an issue with the small VR for adjusting voltage as this should be a 1 time adjustment.

At 67.00 shipped this could very well be the best value in in power supplies on the market right now. Do not be afraid of this power supply. Only a 4 due to it needing a better power cord and fuse.

AG6IF Rating: 5/5 Feb 29, 2012 10:34 Send this review to a friend
a great deal, solid supply  Time owned: 0 to 3 months
I bought this off of Ebay for $67 shipped. Found it to be very stable and great and cheap. I have not found any noise being generated on HF, 6m 2m or 440. Compact size. My power leads are homebrew, using 3 spades on one end and a ring on the other. Each cable is 3x16g for around 50amps of total capacity.
I had to shrink the width of the spades slightly to get them inserted under the hold down clamps.
KUUNABEACH Rating: 4/5 Jan 26, 2012 23:34 Send this review to a friend
Good, but who makes it?  Time owned: 0 to 3 months
I bought this from the ebay seller and while I am pleased with the cost, there are some concerns. First, do a little googling. The genuine Mean Well supplies are well regarded and used in a lot of commercial equipment, This unit and similar from other sellers under names like Mega Watt (this seller), and M&W, MW and other variations of the MW naming look almost identical, down to the the changed fan speed lable. The unit I recieved did in fact have low ripple and the current capacity indicated, however, if you compare it to a genuine Mean Well at $150 from Mouser or others, you have to ask why the price is so much lower. I look at a lot of China products and it seems to me these may be over runs, rejects that failed QC or even knockoffs. Mean Well is a good brand. I'm not sure this product is a real Mean Well.

Further, once connected to a real live radio load, I noticed outright tones all over the AMBC band, but not on HF. Without a load, or a small load all is well.

I will update this review including my packaging efforts placing this into a nice aluminum cube PC chassis I had, including fuses, air management, powerpoles, meters and all the other gak.

I'm pleased overall, but who really makes it? and is it equal to a $150 Mean Well?

I also found the identical product on a China website for $36 each on a 5 piece buy. Not branded Mega Watt, but another variation on MW. I suspect this is some of the same stuff MFJ is selling in a package. YMMV.
KF7QLJ Rating: 5/5 Nov 24, 2011 13:21 Send this review to a friend
Very GOOD value  Time owned: 6 to 12 months
I have been using this power supply for over 6 months to power a pair of Icom 2200H's. It has performed perfectly, just make sure you adjust the voltage when received, mine was less than 11.5 volts on start up, but adjusted right up to a solid 14V. Runs cool with a very quiet fan. I'm going to pick up another one..
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