# MPJA Power Pack Problem?



## rbwhale (Sep 15, 2008)

My Ultima gave up the ghost last night, so I ordered one of the 24 Volt 12.4 Amp power supplies from MPJA; I had seen discussion of them in previous posts. However, I did NOT read _all _of the posts, and the later ones, in May, discussed a possible problem with an over-sensitive circuit breaker. Has anyone experienced circuit breaker problems with this power supply? If so, is there a reasonable fix, like a different breaker, or substitution of a fuse? Or have I, in my quest for a bargain, shot myself in the foot?


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## rbwhale (Sep 15, 2008)

well...I'm hoping the total lack of response to my questions means there are no problems with the power pack. It should arrive any day, so I guess I'll find out soon enough. Wish me luck....


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## Greg Elmassian (Jan 3, 2008)

I saw the post but have no experience with them. The fact they are so inexpensive would seem to say they cannot have the same quality components as the typical prices you see for switching power supplies. 

The lack of replies is probably lack of experience, not a lack of problems per se. 

Regards, Greg


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## Totalwrecker (Feb 26, 2009)

I got one, just haven't used it enough to give a qualified reply. 

I think the company was downsizing their product line and they were close-outs. 

MPJA is a clearing house, what brand name has the bad part? 

John


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## Greg Elmassian (Jan 3, 2008)

I looked at the illustrations on the site, they were not Meanwells, but that's not the only good brand of low cost switchers. 

Regards, Greg


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## Dan Pierce (Jan 2, 2008)

The supply is a Potrans and they are constantly 'getting rid of them'. 

2 months ago there were only 57 left, Today they are down to 346 left, yes, 346!! 

Someone is buying these and reselling them for lots of $$ on E-bay. 

$25 each, $20 if you order 48 f them.


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## Totalwrecker (Feb 26, 2009)

Rot Roh same brand... Mine's model #FS-32024-1M 

But as I said; too new to know, 'cept I wish it had been 'over-sensitive' before the blue smoke... 

John


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## Greg Elmassian (Jan 3, 2008)

Ahh, I am familiar with that company... yep very inexpensive power supplies from China... Have seen that name on a lot of the PC power supplies when I buy the "loss leader" PC chassis. 

Regards, Greg


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## rbwhale (Sep 15, 2008)

Well, thanks, at least I don't feel like a voice in the wilderness any more. What exactly should I be looking for in terms of problems? Jerky operation...slow speed...? 
I will be using the 27Mhz Train Engineer.


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## Greg Elmassian (Jan 3, 2008)

The only problem you might encounter is the supply failing. 

Depending on how it fails, I would guess you either will get zero volts (trains do not run at all), or unregulated DC (train thinks it is bullet train in japan). 

Put a fuse in the output, and don't worry, usually when a power supply fails, all the smoke comes from the PS. 

Regards, Greg


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## krs (Feb 29, 2008)

Posted By rbwhale on 03 Aug 2009 02:26 PM 
My Ultima gave up the ghost last night, so I ordered one of the 24 Volt 12.4 Amp power supplies from MPJA; I had seen discussion of them in previous posts. However, I did NOT read all of the posts, and the later ones, in May, discussed a possible problem with an over-sensitive circuit breaker. Has anyone experienced circuit breaker problems with this power supply? If so, is there a reasonable fix, like a different breaker, or substitution of a fuse? Or have I, in my quest for a bargain, shot myself in the foot?



News to me that these switching supplies even have a circuit breaker - where did you see that comment?


Potrans supplies are dirt cheap because the company has gone out of the power supply business. That's what their distributor in California told me.
They certainly look like great supplies on paper.
They also have over-voltage protection built in, so your trains are pretty safe.


knut


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## SLemcke (Jun 3, 2008)

I bought mine from MPJA about a year and a half ago and have had no problems. Liked it so much I bought a second one. as a spare when they were on special for $14.00. I have the Massoth 1210Z central station. But I have not set the amp rating to 12 yet only at 7. Haven't even come close to maxing it out. I also haven't run outside in over 95 degree temps. 
Steve


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## barnmichael (Jan 2, 2008)

Many of these type supplies have a fuse mounted on the circuit board inside. However, they are on the hot AC input. I have rarely seen a circuit breaker on the power supply itself. I strongly recommend under-rated fast blow fuses on these supplies. If you have a 12.5A supply, use a 10A fuse. Fuses are always cheaper than power supplies. If you keep blowing fuses, you have a problem or are pulling too heavy of load. Fix the problem, don't put in a larger fuse. Decrease the load (take off a few cars) or get a bigger power supply.


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## Greg Elmassian (Jan 3, 2008)

That's the fuse on the output I recommended. Not sure I would specify a "fast blow", just a normal blow should be fine. Maybe you were trying to make sure he did not get a slo-blow. 

On most "normal" fuses, it's typically a little-known fact that the fuse usually lets go at 200% of it's rating, so a 10 amp will let go at 20. So, as Michael stated and "under-rated" fuse, if you are really concerned, a 5 amp fuse on a 10 amp supply where you typically only pull 7-8 amps can make sense. 

Confused yet? 

Regards, Greg


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## krs (Feb 29, 2008)

Posted By Greg Elmassian on 08 Aug 2009 06:17 PM 

Confused yet? 


I bet you some people are.

The input fuse mentioned earlier is a red herring.
It's not intended to be user replaceable. If it blows, something in the power supply has become defective and has to be fixed.


Adding a fuse at the output of the supply can't really hurt but these supplies already have a lot of protection built in - short circuit protection, over current, over voltage and over temperature protection as well.

I have run my switching supplies from Meanwell for more than ten years now with never a problem.
On over current or a short, it just shuts down and then automatically powers up a again as soon as the short is removed.

For the ones sold by MPJA it sounds as if you have to recycle the AC when the supply shuts down,

Knut


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## Totalwrecker (Feb 26, 2009)

Well I wasn't until you mentioned recycling AC... is that a green thing?


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## Greg Elmassian (Jan 3, 2008)

I use the Meanwell with success so far... I only recommend fuses if the overvoltage circuit fails, which can happen. Cheap and easy insurance. 

Regards, Greg


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## Dan Pierce (Jan 2, 2008)

I do not agree that when a fuse blows that there is a problem with a power supply. 

I always suggest that a replacement fuse be tried once as sometimes fuses blow due to age and sagging elements. BUT if it blows the replacement right away, there is a real problem. 

I have had many power supplies blow the fuse only once. 

Some blew the fuse due to a power surge.


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## Greg Elmassian (Jan 3, 2008)

To be clear, I am recommending a fuse on the output, for protection from a short on the output, or the rare case where the supply fails and also the overvoltage circuitry fails. 

I'm not talking about the internal fuse, nor a fuse on the 110v side. 

And I have indeed seen fuses age and blow for no apparent reason exactly as Dan states. Sometimes the fusible link just fractures with age, then it will blow prematurely. 

Regards, Greg


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## krs (Feb 29, 2008)

Posted By Totalwrecker on 08 Aug 2009 10:20 PM 
Well I wasn't until you mentioned recycling AC... is that a green thing?



Not sure if you're being funny or if you really don't know what recycling AC means.

Term we use for turning something off and then on again.
It's also the terminology used on the power supply data sheet.

So with shorted output the supply shuts off and stays shut off even after you remove the short or overload. You need to turn the input power off for the circuit to reset.


knut


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## Totalwrecker (Feb 26, 2009)

Thanks, I didn't know and used humor to mask my ignorance. 

Often I know you guys are talking between yourselves. I follow along and pick up what I can. When youse guys (friendly term) started talking about us guys, the confused, I sensed an opportunity to speak up without interrupting. 

Compooters have taught me the need to reboot, without really telling me why. Your kind explanation helps me understand and see the similarity... Oh OK makes sense. 

Thanks, 
John


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## krs (Feb 29, 2008)

Posted By Greg Elmassian on 09 Aug 2009 08:53 AM 
And I have indeed seen fuses age and blow for no apparent reason exactly as Dan states. Sometimes the fusible link just fractures with age, then it will blow prematurely. 


Agree - that certainly does happen, not very common though.

The original post was about a "sensitive" circuit breaker. However, I can't think of any switching supply that incorporates a circuit breaker at the output - the one referred to in this thread certainly doesn't.

But by "cicuit breaker" I automatically think of a mechanical device not a crowbar circuit or current limiting circuit that's incorporated in this supply - maybe there is confusion because of the terminology used.


knut


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