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Reviews For: MEGA-WATT S-400-12

Category: Power Supplies

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Review Summary For : MEGA-WATT S-400-12
Reviews: 19MSRP: 65.00 + 5.00 SHIPPING
Description:
SWITCHING POWER SUPPLY 13.8 VOLTS DC AT 35 AMPS 80% DUTY CYCLE 30 AMPS 100% DUTY CYCLE
Product is in production
More Info: http://EBAY SELLER ELECTRONICS_5000
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
00194.1
KA9HJZ Rating: 2017-07-12
Works like they said it would. Time Owned: more than 12 months.
After I received this power supply , I got a little worried, it was small and light weight, I thought well I will give it a try and hope for the best. I have been using it with my old Ten Tec Paragon and so far have never had a problem. The reason for the 4.5 rating is because I only transmit around 70 watts. I have run it without ever turning it off for as long as I had it, except for maintenance on my radio and a few tests on my other rig. I also used it with my Kenwood 590 S to see how it worked. The cooling fan is as quiet as it was when I bought it. Maybe I was just lucky and if it does finally go Kaput. it cost me no more than 60 bucks.

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Earlier 4-star review posted by KA9HJZ on 2016-09-21

I have used this PS intermittently for over a year, I was surprised how small it was, I use it for a Kenwood TS 590 and My old Ten Tec paragon, I never use more than 70 W power so I don't know how it would perform powering 100 watts or Teletype for any length of time, it does have a on/off switch on the power cord, which is a good idea. bought it from the company on line, which makes it a little cheaper in cost. Be careful when buying from Ebay because there is a look a like that is not as good, being sold at a lesser price The fan does not bother me as far as noise goes, I keep the PS. several feet from the radio.
KD9WXB Rating: 2017-04-05
Awsome Time Owned: more than 12 months.
The megawatt has been an awesome power supply for my shack. I have used it constantly for two years without issue. The owner of megawatt, John, has been so helpful with all my annoying emails about setup and changes I wanted to make my system. I've now bought a second one I used to power my two pill. A super good quality, free of RFI and I love customer service.

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Earlier 5-star review posted by KD9WXB on 2015-10-25

I have had my S-400-12 running 24 hours a day for 2 years now. You can't get any better for the price. It truly is one of the few switching power supplies with no RFI.
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Earlier 5-star review posted by KD9WXB on 2014-08-22

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.
KE0EYJ Rating: 2017-03-31
Died after 3 months Time Owned: 0 to 3 months.
Worked fine for three months, but now powers on with no power output, and a high-pitch noise from fan. Will have to contact for warranty work. Sadly, I live overseas now, and will have to try next summer when I return home. I may still be under warranty. These units are really extremely light. Too light. Like the ultra cheapest of the cheap computer power supplies are. I simply turned it off, and it would not turn back on a few hours later. By the way, I really wish Eham would quit editing my review of this. The owner of Megawatt sent me a threatening e-mail, after seeing my negative review of his power supply. He threw a bunch of legalize at me, about what reasons warranty work wouldn't be free for, and then strongly hinted that I would need to update my review, if I expected warranty work. I have never been treated like this by a seller -- ever.

Going to buy a heavy Diamond brand power supply next, and hope they replace this. I will use that for a backup or something.

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Earlier 1-star review posted by KE0EYJ on 2015-10-10

Worked fine for three months, but now powers on with no power output, and a high-pitch noise from fan. Will have to contact for warranty work. Sadly, I live overseas now, and will have to try next summer when I return home. I may still be under warranty. These units are really extremely light. Too light. Like the ultra cheapest of the cheap computer power supplies are. I simply turned it off, and it would not turn back on a few hours later.

Going to buy a heavy Diamond brand power supply next, and hope they replace this. I will use that for a backup or something.
W3ATT Rating: 2016-10-09
Good Power Supply Time Owned: more than 12 months.
If you are careful with your installation, you won't have any birdies or hash with this supply. I once moved my shack around and put the supply under a different desk which produced hash about every 50-60 hHz... Moved the supply back under my computer desk and all hash is gone again. I don't really know why this is, but all that aside, this supply has been running EVERY single day for the past 3 years with no issues. It never bogs down for power when running full 100 watts, CW. And, unlike supplies with big transformers, this thing has absolutely NO AC HUM! The little cooling fan makes a littls bit of noise, but nothing compared to the annoying 60Hz HUM that I was getting from an Astron RS35M (HUGE hum coming from transformer that got very loud on every dit and dah (under load at 80+ watts..)) In summary, I went from this switching supply to the Astron and went back to the Mega-Watt less than 24 hrs later. Just my experience.
N8WGM Rating: 2016-01-30
excellent choice so far Time Owned: 3 to 6 months.
I purchased my S 400-12 off E-bay. It seems to work well so far.

Yes, the fan is rather noisy. I fixed that by installing an external higher quality fan which was much quieter and yet gave more air.

So far it has powered my Kenwood TS480HX rather well along with my Alinco DM-330MV.

I would say that for the price, you cannot beat this power supply. Just be prepared to modify it for better service.

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Earlier 4-star review posted by N8WGM on 2015-10-31

So far I recommend this power supply. The fan is a bit noisy but that can be fixed with a better fan.

It does put out the power I need and has no hash on any frequencies I am on. A pretty good deal for around $70.

A lot smaller and lighter than the Astrons that I have used in the past. The Astrons are tanks compared to this but I like small and light.

Will it last as long as my 35 amp Astron? Not sure but the switching technology is taking over.

I recommend this power supply so far. For the price.....well it seems to do the job it was designed to do.
W5JV Rating: 2015-07-17
Support As Listed Time Owned: more than 12 months.
One of my Mega-Watt S-400-12 supplies failed after about 18 months. I contacted the seller (still on eBay) who promptly replied, verified it had a 24 month warranty and invited me to send it in for repair. The supply was quickly replaced with a new one for $10 shipping cost. The new supply was installed, tested and ran great. I was told "the TL494 was damaged by a voltage spike". The TL494 is a 16 pin regulator IC that is apparently the heart of the power supply's control circuitry and not immune to AC line transients. I thought my station was immune to this because of installed surge suppressors but apparently not. The unit did not fail during use, it was dead when I turned it on to use it. So, from now on I will unplug it when not using it. Hope this helps someone else. I'm leaving 4 stars because it seems like in this day and age designers could have learned how to protect their A/C inputs from routine voltage spikes by wiring in MOV's or whatever they use for this issue.
AD0AR Rating: 2015-07-10
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
KA7NIQ Rating: 2013-07-06
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: 2013-06-03
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: 2013-01-10
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.