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Reviews For: MFJ-4245MV

Category: Power Supplies

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Review Summary For : MFJ-4245MV
Reviews: 68MSRP: 150-200.
Switching and Non-Switching Power Supplies
Product is in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
N7BTH Rating: 2019-02-23
Fan Noise Time Owned: 0 to 3 months.
Many others here have tested the limits of this power supply. I have not as I only use it to power my VHF/UHF Icom for weekly net check in. When set to 13 volts for that purpose the fan runs full speed, even with no load on it. The "variable" part of the fan speed comes in as you dial down the voltage output. Down at about 5v the fan is pretty quiet but at 13 too noisy for me. Will ether need to install a bypass switch or move it farther away from the rest of the station which is inefficient and not very convenient.
WD8RLJ Rating: 2018-08-26
Intermittent Power on Start up Time Owned: 6 to 12 months.
Less than a year operation and never worked. I find the supply fan light flickers and the device will not start up. However, after several attempts, it finally MAY start up. Interesting how the fan light flickers and that is all she has Captain.
AC6BW Rating: 2018-05-17
Working fine after 4 years Time Owned: more than 12 months.
I've owned this power supply for over 4 years. It powers all of my HF gear. I've had no problems whatsoever with it. I do not push it near its current limit, however, I do operate it for long periods of time, sometimes entire weekends, running high duty cycle modes in contests. The fan noise is not very loud. My tube based linear amp has a louder fan than this supply. I have not had any problems with voltage ripple or hash. I agree with another reviewer, that folks who have had a positive experience should take the time to post a review.
WA2ZQX Rating: 2017-11-21
Noisey Time Owned: more than 12 months.
Failed during first week...loud pop...fuse okay. Returned to MFJ. Got it back five weeks later after a number of calls. It has been good since. Fan noise is very loud...and so annoying. Also have a Powerwerx SS-30DV power supply...very quiet fan, 1/4 the size and no problems. My HF-AMP and Transceivers are whispers compared to the racket made by the MFJ-425MV.
ISOAR Rating: 2017-10-19
Danger Will Robinson! Danger! Time Owned: more than 12 months.
This is an update on my first review. Rating "poor" and not "awful" because it hasn't yet fried anything of mine in the years I've owned it.

Keep in mind that my unit is an older model, and not from a recent production batch.

Today I was in the mood for some hacking, and I wanted to upgrade the meter lighting to white LEDs like the newer models. The incandescent bulbs have always annoyed me with their warm colour, and non-steady brightness.

I first Google-ed to see if anyone else had done it, and only found one comment about the bulbs not looking replaceable.

However, I also found a curious mention of someone else replacing the output capacitors and load resistor. Upon a closer look, I agree, 16V caps always bugged me too that they were not at least 25V, and the load resistor (3W) really should be 10W given its bad location with no cooling, and preferably moved to a position near the fans.

Upon opening the case, I was taken aback by the LARGE number of flying components! There was more to be concerned about too.

Instead of using crimped lugs for the binding post connections, the positive wires (2x 16 AWG, 105 degC) are soldered directly to the binding post screw, making them non-removable. So the front panel is non-removable, and access to the meters to replace the bulbs is not possible.

It was at this point when I realized there were no ground return wires from the board output! Just the frame ground near the AC input.

The ground output binding post is connected directly to the frame (2x 16 AWG). There is a hole in the case next to that likely for the board ground wires to be anchored.

All 45 Amps would have to go through the SEC metal case, to the board mounting posts and M3(?) screws, or the AC frame ground connection (1x 16 AWG)!

Salvageable. Luckily I've never shorted it, nor drawn a heavy load!

I should be able to drill into the top of the meters, and insert LEDs there. Simple matter to clip the bulb wires, and add in a linear regulator for the LEDs to be at a constant brightness.

I'm also planning to add a crowbar, probably external.

Lastly, I'm now looking for a power supply replacement.
KJ4SSX Rating: 2016-03-21
This is a great little power supply! Time Owned: more than 12 months.
I have owned this power supply for almost 2 years now. I have over loaded it many times and it resets itself every time. I am ordering another to power an solid state amp so I won't keep over loading my primary one. MFJ's no questions asked warranty is great.
KT8DX Rating: 2015-05-16
Never a bit of trouble Time Owned: more than 12 months.
I've owned mine for many years now - probably about 10 or so. Fan is quiet, and I've shorted mine many times accidentally with no ill effects. It just chuggs away and powers my HF rig and VHF radio as well. The reviews here are scary but perhaps the older ones were better built. I do think I'll take mine apart and just check all the solder connections just to be on the safe side.

Over the years, I've always liked MFJ - some things I've bought have been absolute junk, but when I got the replacement it was fine. QC certainly seems to be a problem but if you get something that is a "good one" you are usually in decent shape.
LU1AW Rating: 2015-03-31
OVER-VOLTAGE PROTECTION Time Owned: more than 12 months.
I've been using the MFJ-4245MV for over three years @ full 7/24 service. You do the maths but it is a damm pretty high number of continuous hours on.
Along all that time, it had its share of AC pwr outages but It never fails powering my remotely controlled CW station (FT1000MP). Fans are a bit noisy. Unless you use headphones it'll

bother you.

I've read a bunch of posts here about this PS having fried their connected equipment due to an over-voltage event and also claiming this PS doesn't have over voltage protection.

Well, I must say IT DOES.
Check the schematics and you'll see a diode (D11) attached to port 4 of IC TL494. Trace it all the way up to output and note the it goes to through 3k3 resistor AND 16V ZENER and a 100

ohms 3W resistor connected right to the output. THAT IS THE OVERVOLTAGE CIRCUITRY.

Port 4 on the TL494 will shutdown output if sees a positive voltage higher than the normal it references from ref. 5V in the IC. If an over voltage condition exists in the output exeeding

about 16 volts or so, it'll pull the Zener into conducting state and will rise the voltage at port 4 (DTC) via D11 which in turn, will decrease or shutoff the output. You can test if it is working

just by shorting the 16V Zener (as if it was a 16 volts over-voltage condition at the output) the output should dropp to zero. Once removed you'll have to wait some seconds for the PS to


This describes the over-voltage protection circuit which might fail if either D11, 16V Zener or the two associated resistors get the path open between output and pin 4 of TL494.

It also could happen if the feedback path gets open (R33-R34 or VR2)
MFJ4245mv also have short circuit protection. I´ve done both tests on mine.

Definitively the MFJ-4245MV DOES have the protections by design, BUT poor component quality and/or solder affecting any of the paths from output to pins 1 and 4, will void the

overvoltage protection.
Check for those components and solders and do the testing before any possible failure fries all connected equipment.

Oh! yap! the picture in the review is not the MFJ-4245MV

Juan, LU1AW
N4ZAW Rating: 2014-12-01
I changed my mind about this supply! Time Owned: more than 12 months.
After owning this supply for as long as I have, I figured it was time to re-review it. I gave it a "1" the first time, only because of MFJ's unmatchable 'unconditional one year guarantee' -- which I obviously THOUGHT I had to use... I had to switch the second one out with my garage supply (where I like to work on radios and such) because it tripped-out at 30amps. And yet, it has been ROCK-SOLID out there for five years, sees daily use! Since 2009, and has been "rode hard and put away wet"! It has been subjected to repeated short circuit shut-downs, always resets, and comes back swinging! The issue with running it in the radio room might've been RFI caused by a defective filtering from my Yaesu FT840, but I'm still not certain of that. I don't think I could rely on it as a shack supply because of that issue and the fan that sounds like a "Wright Whirlwind", but I must admit -- though it trips "RIGHT NOW" when a dead short is detected, it has NEVER tripped when placed under consistent high demand (in the garage, anyhow)! It responds very quickly if you touch the outputs! It's a "keeper". Still, I am only raising that original "1" to a "4" instead of "5" because the fan is very loud for a voice communications environment.

Earlier 1-star review posted by N4ZAW on 2009-09-02

I give it a 1 out of 5 only because it comes with the MFJ unequaled 1 year unconditional guarantee -- NOT that I am going to send the SECOND one back. The first one consistantly cut-off at 30AMPS.. This one (a week old), cuts-out a 20AMPS!!! MFJ swapped the original for a brand new one right off the line after only 2 weeks of waiting... I sure wish they would've aligned the stinker first!!!
I put it back in the box and brought the Astron SS-25M it was to replace back into the shack.

BTW, If anyone knows how to adjust the current cutoff circuit to it's proper level, let me know!!!!
What a pain! What ever happened to "Made in the USA"?
KU4AA Rating: 2014-08-23
DO. NOT. BUY. OR. USE. THE. MFJ-4245MV. Time Owned: more than 12 months.
Please, if you value your expensive ham radio equipment, do NOT buy the MFJ-4245MV power supply. If you are one of the owners of this power supply, PLEASE take it out of service immediately!!! You are playing a dangerous game of chance each and every time you use this power supply. I am dead serious, and wish to warn you before you kill your radio equipment.

I came out to the shack this evening to see what was happening out on 20 meters. I reached over to flip the switch on the MFJ-4245MV, and noted that the meter was indicating around the 13.8 volt level. I then pressed the power switch on my Yaesu FT-847 to bring it up. Immediately, I heard a loud pop from the power supply, the meter pegged high, and the panel lights and fan indicator instantaneously became VERY bright. As I already had my finger near the FT-847 power switch, I quickly punched the switch to kill power on the transceiver--but I suspect that the damage is already done. I will need to wait a couple days to access another power supply to determine if the transceiver is fried or not.

As for the power supply, I removed it from the shelf, repowered it with only my Fluke meter attached, and it drove up to 31.16 volts and begain a high-pitched squeal (likely the switcher). I could probably fix the power supply myself, but what is the point? Like Ian, KC2YXU, stated earlier, I will never be able to trust it to power anything, especially if there is the chance that it will overvoltage for any reason. Many of the reviewers here had a momentary short circuit which precipitated the failure; I simply turned my radio on. If this power supply can be damaged with only a 2-3 amp surge, and kick up to such a horrendously high voltage that it will kill a transceiver, why would I want to fool with it?

Why would YOU want to take that chance?

Please, don't buy this power supply, and please stop using it, for your own sake. I had mine for a year, and it worked flawlessly except for one time. One time is all it takes.

Jim, KU4AA