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MFJ-4275MV 75 Amps Switching Power Supply Review

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,052
1,365
283
Loading one of these supplies up to about 80 - 85% of its Peak load specification and have a look at the output with a 'scope. With AC coupling in the vertical channel, you should see ripple and noise that is less than 100 mV. Anything greater, including momentary spikes, will be detrimental.

While you may not hear anything objectionable in the speaker, it is quite possible that it will affect the transmitted signal, or the decoding of a digital signal such as PSK, JT65 etc.

As far as I am concerned, for the value, a linear type of supply, while not being as efficient as a SMPS, is a much better value in the ham shack.

I agree with your perspective. Unfortunately I have long sold off my scope, so I can't perform the test you suggest. I've spent some time on digital modes and haven't noticed any issues yet, but I'll keep an eye out. This supply probably isn't "lab grade", but in my mind, the question is if it's "good enough" for the ham shack.

I had a big 100 amp linear supply that this replaced, but I was running out of room. Sometimes size constraints drive the choices we have to make.
 

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,052
1,365
283
Operational Thoughts

I've been using this supply powering the majority of my station for about 2 months at the time of this post, which is long enough to share some overall thoughts about its operational characteristics.

First, the power supply is noisy compared to a linear supply, but this tends to be the nature of larger switching supplies. The supply has two cooling fans which run the entire time the supply is under load which generates the noise. The supply does increase or slow the fan speed based on the supply load and resulting heat that is generated. Interestingly, the supply also makes a slight hissing sound anytime it is powered on when there is no load. The fan noise is no worse than the linear amplifiers I own, so it's not a big deal to me. For the operator looking for as little background noise as possible, you might want to choose a linear supply or find a switching supply that is quieter.

To test the current capabilities, I attempted to put a max load on the supply by having a lengthy conversation on 2 meters driving a 200 watt VHF amp with a 50 watt radio in combination with a 100 watt continuous HF transmission in to a dummy load. According to the supply meter, I was drawing close to 70 amps. Because I was monitoring the transmit power output on both HF and VHF, I was able to observe that the station showed no sign of power strain .
 

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,052
1,365
283
Summary
These are my summarized thoughts on this power supply. The positives are that it's small and light weight for a supply that can deliver 75 amps of current. I REALLY like all of the wire terminal choices and I also like that they are on the front. If you don't play with a lot of different types of equipment, disconnecting and reconnecting, you would probably prefer that the terminals were on the back. Variable voltage and meters are a nice touch, and I LOVE the battery charging feature. The negatives are that it is noisy (this is not necessarily unique to this switching supply) and that it probably could have better RFI filtering designed in. While I haven't personally experienced any problems with RF hash, I will be keeping a close eye on it.

In my mind, this is one of those types of products that are "good enough" for what I need in the ham shack. As long as I don't start to experience RF hash, I will be happy with it as it gives me much more room for other radio equipment
 

Se7en

Well-Known Member
Jun 27, 2010
4,576
219
73
Ca
Summary
These are my summarized thoughts on this power supply. The positives are that it's small and light weight for a supply that can deliver 75 amps of current. I REALLY like all of the wire terminal choices and I also like that they are on the front. If you don't play with a lot of different types of equipment, disconnecting and reconnecting, you would probably prefer that the terminals were on the back. Variable voltage and meters are a nice touch, and I LOVE the battery charging feature. The negatives are that it is noisy (this is not necessarily unique to this switching supply) and that it probably could have better RFI filtering designed in. While I haven't personally experienced any problems with RF hash, I will be keeping a close eye on it.

In my mind, this is one of those types of products that are "good enough" for what I need in the ham shack. As long as I don't start to experience RF hash, I will be happy with it as it gives me much more room for other radio equipment

Max voltage output with Max current ?

Sent from my Xoom using Tapatalk 2
 

Kikker

Member
May 31, 2013
28
5
13
ad my MFJ 4275MV for about 6 months. It has been doing a great job powering my entire station. The MFJ power supply runs my ICOM IC-718, ICOM IC-R7100, TX Star Mod-V PLus and Messenger 350 on a daily basis. Everything I currently have in service runs off of 12 volts. I was impressed that the MFJ 4275MV handled the load of my Messenger 4V very well. I had heard from other that a 4V would need at least 100 to 125 amp power supply by itself but that simply isn't true. At most with the Messenger in high gear it draws about 60 to 65 amps. Naturally I wouldn't want to work the power supply that hard for long periods but I don't run the amp in higher at all of the time anyhow.
 

hotrod

Well-Known Member
Feb 16, 2007
2,463
309
93
n.w pennsylvania
after several months of use i really like my jetstreme 75 amp p/s.
it does have a noisy fan that is notable without a load. thats my ONLY
complaint.thought bout calling my tech see if it can be hooked up to
a toogleswitch. it replaced a pyramid 52 amp p/s [which is as big as a 2990]
and very heavy. and a 36 amp pyrmid. the jeststreame is lighter than both
and powers everything i got.i havent noticed any rfi in the recieve far as
i can tell.
 

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,052
1,365
283
UPDATE

After owning this supply for more than 6 months and using it regularly, I can safely report that this supply DOES put out quite a bit of hash that affects the HF bands. It exhibits itself in the form of something that sounds like a moving carrier (I might try to shoot a quick video so readers of this post can actually hear for themselves). It is also visible in an attached panadapter.

I've been doing quite a bit of research on RF hash caused by switching power supplies, and while the problem is not as bad with lab-grade, expensive supplies, those are probably out of the reach financially from most hams. I have found a fairly decent solution to the problem with this MFJ supply that is fairly affordable - I will post details soon.
 
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CTStallion

Active Member
Aug 29, 2010
196
21
28
Connecticut
UPDATE

After owning this supply for more than 6 months and using it regularly, I can safely report that this supply DOES put out quite a bit of hash that affects the HF bands. It exhibits itself in the form of something that sounds like a moving carrier (I might try to shoot a quick video so readers of this post can actually hear for themselves). It is also visible in an attached panadapter.

I've been doing quite a bit of research on RF hash caused by switching power supplies, and while the problem is not as bad with lab-grade, expensive supplies, those are probably out of the reach financially from most hams. I have found a fairly decent solution to the problem with this MFJ supply that is fairly affordable - I will post details soon.



Definitely would like to see what you come up with as a remedy.

Thanks and Good Luck!
 

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