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MegaWatt vs. Chinese Imitation 30 amp switching power supply comparison

Discussion in 'Product Reviews' started by Moleculo, Mar 19, 2015.

  1. 338_MtRushmore

    338_MtRushmore Sr. Member

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    He said it was a ground loop. I haven't even powered anything with the supply, just powering up the supply itself. I guess I will try isolating the plug ground and see what it does.


     

  2. jon666

    jon666 Sr. Member

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    i have 3 of them no hash at all.
     
    Tallman likes this.
  3. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    I bought one of the other brands just to see how they worked. I hooked it up and put a load on it. It was primitive load but it works. I used car head light bulbs mounted inside of a metal down spout and have a centrifugal blower moving air through it. I monitor the current and flip switches until I get the current load I want. The "Other Brand" had more birds than a pigeon feeding station in New York City. I modified the test load so I could Pulse load the supply 10% or 50%. The 50% load caused unstable voltages with a two volt variance. I took the megawatt unit and subjected to the exact test and the maximum variance I saw was only about 250 Milli-volt change. No birdies either.
    I was some what puzzled by the test result and opened them both up. The cheapo unit lacks a substantial amount of power filtering compared to Megawatt unit.
    It takes more than a few Capacitors to give a good regulated output. Compensation networks in the switching circuits have to be tuned in for proper regulation. To much compensation and it will ring and oscillate, too little and the voltage will sag and slowly recover. I'll look and see if I can find all of my test results.
     
    #138 Tallman, Jul 14, 2019
    Last edited: Jul 14, 2019
    BenMara, 357magnum, S&W357 and 2 others like this.
  4. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Dynamic load testing is what matters in communications duty ESPECIALLY where any form of amplitude modulations is used including SSB. IMD can go all to hell if the power supply voltage is wandering all over the place with varying loads on voice peaks. Most people do not understand this or even care but responsible operators do.
     
  5. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    I just want my equipment to operate properly. The CHEAPO supply I would not even connect it to my radio. I'll just use it for LED power supply or rust removal.
     
  6. CrAcKeR1710

    CrAcKeR1710 New Member

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    So, I kinda hate to ask, but did John aka Mr. MegaWatt sadly die or something? He hasn't been seen on this website for over 33 weeks at time of this post!!

    "Megawatt was last seen: 33w 1d ago"

    I'm just wondering about the loud fan noise and if it ever got resolved? :(
     
  7. S&W357

    S&W357 WDX-556 / 2NC357 Supporting Member

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    I bought my second S-400-12 a couple of months ago. No problems with the first one and never thought it was noisy. Listen hard and I can hear it...yes.

    Second one had mention in paperwork of “now with quieter fans”. It does seem quieter than the first one.
     
    357magnum likes this.
  8. 2315 Robert

    2315 Robert Grateful

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    Will send John an email.
     
    S&W357 likes this.
  9. 2315 Robert

    2315 Robert Grateful

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    Hello, yes the S-700-12 is 1/2 the volume it used to be and soon the S-350-12 and S-400-12 will be almost silent. Above ground????? They are buying 100s of power supplies a week. Somebody is shipping them:)
    Thank you,
    John

    Wanted to make sure he was above ground. He is. Those new specs look great.
     
    S&W357 likes this.
  10. S&W357

    S&W357 WDX-556 / 2NC357 Supporting Member

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    Oh yes, he's above ground. Each time I've ordered a PS from him I receive an email with ship date, delivery confirmation number, and a "thank you".

    Upon receipt of PS I send him an email acknowledging receipt of the PS. Within a day or two I receive and email back from him..

    Anytime I'm talking on my AT-6666 set up as a base radio I'm using two of the S-400-12 PS's...one to run the radio and one to run a two-transistor amp.

    Bottom left corner of picture. (y)

    [​IMG]
     
    357magnum and Shadetree Mechanic like this.

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