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Reviews Categories | Power Supplies | MFJ-4245MV Help

Reviews Summary for MFJ-4245MV
MFJ-4245MV Reviews: 71 Average rating: 3.0/5 MSRP: $150-200.
Description: Switching and Non-Switching Power Supplies
Product is in production.
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WA2ZQX Rating: 2/5 Nov 21, 2017 05:03 Send this review to a friend
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: 1/5 Oct 19, 2017 00:34 Send this review to a friend
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: 5/5 Mar 21, 2016 07:34 Send this review to a friend
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: 5/5 May 16, 2015 12:32 Send this review to a friend
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: 4/5 Mar 31, 2015 12:57 Send this review to a friend
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. Ive 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: 4/5 Dec 1, 2014 09:13 Send this review to a friend
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.
KU4AA Rating: 0/5 Aug 23, 2014 18:50 Send this review to a friend
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
AA2SM Rating: 0/5 Mar 9, 2014 22:21 Send this review to a friend
Sounds like a lawn mower  Time owned: 0 to 3 months
I had owned a 4225 and had superior performance from it over the years. when I dropped it in my shack moving things around, I decided to get the 4245 model. I really hate to say negative things about a product, sometimes thinking its me. But I can honestly say that this is a real piece of crap. From day one the fan was super loud. I started to get a hum noticed in my headphones which increased as a higher voltage was applied. Finally at around 13 volts it sounded like my lawn mower in my headphones and on the air. Had three other hams in a row tell me I had a loud hum along with my transmit. My forte in radio is cw and boy this was annoying I wished I read these reviews before I purchased it. My only thoughts now is that there should be a law against producing such a monster which could potentially ruin your rig. Went back to the 4225 and everything is quiet and great again. I hope that my fellow hams that gave this a 5 rating, have all the luck in the world with it. Yes its big and some would say pretty. So was the Titanic
VK2BJP Rating: 0/5 Mar 4, 2014 12:31 Send this review to a friend
Piece Of Junk  Time owned: 0 to 3 months
Bought this ps switched it on, it ran for 10 minutes @ 21 amps when I try to increase power on the tx that is draw over 21 amps the ps thinks it overloaded and shuts down, very poor quality.
This is the second piece of junk I've bought from MFJ, I won't be caught again
AI4HO Rating: 5/5 Feb 27, 2014 19:41 Send this review to a friend
Ten years still goin strong  Time owned: more than 12 months
I have had my MFJ-4245MV power supply for ten..almost 11 years now. It still keeps chuggin along, no hash, no noisy fan, no RFI issues..nothin of the sort. I find this power supply to be robust, and with the adjustable voltage output, you can't go wrong. This power supply has powered a variety of rigs over the years, Kenwood TS-570 D(G), Yaesu FT-897D, 857D, Icom 706MKIIG, to name a few.

I currently have my MFJ-4245MV loabed out to a relatively new ham who needed a metered power supply, I was one of a couple and the only one who lived near by to have a metered power supply..the MFJ-4245MV. He has been using this power supply for two or three months now with no issues what so ever. That said, these are relatively small and light weight and easily transportable, great for field day use, mine has seen at least 9 field days, and barring any unforseen accidents..will likely see quite a few more field days. These are not that costly to purchase and are well worth it at any price. I have recommended these power supplies to my friends and other hams I have met in my 20 years as a ham. Thanks to all who have taken time from their busy schedules to read my post. I pray you all have a great day.

73 de Mark
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