Switched Mode Power Supply PCB Blowing Fuse - Help!

[s34n]

Hi There,

I need to say first that my electronic experience is very minimal!

I have a PCB from an arcade machine power supply, the whole Power Supply had around 4 PCBs in total and I traced the fault to this PCB. This PCB takes 120V input and (i think) outputs 5V (I measured the 120V, and the wire terminal has a small 5V sticker on it, so I assumed it's +5 -5 and two ground wires). Could somebody confirm?

Here is a video of the board (it came out better than the pictures did, view in HD mode)


When I got the machine, the fuse was already blown on this PCB and the fuse was soldered onto the PCB. I have replaced the largest capacitor on the PCB, then I added a fuse case and a new fuse and it immediately blew, so I suspect something else is wrong!


I removed the bridge rectifier and tested it out of circuit with the 2M setting on the multimeter. The reading began at roughly 3.00 and started to count towards an open circuit. I stopped testing when the multimeter hit 6.53. I placed the probe on the two tildes to test it; which were labelled on the chip itself.
https://drive.google.com/file/d/0B6SfMAw6tfpRVlBoMjh4RTlEcms/view?usp=sharing

The markings of the chip under the clip and plastic state:
MIP0227SY is at http://pdf.datasheetcatalog.com/datasheet/panasonic/MIP0227SY.pdf.

I tested the MIP0227SY while it was still in the board as I had already removed the bridge rectifier . I used the right two pins to test it. I used the 2M Setting on multimeter. The range went from 0.00 and slowed more around 3.49, I assumed it would carry on until it ready an open circuit. When I flipped the probes, it gave the reading as negative and went up to 0 then back up the positive numbers again.
https://drive.google.com/file/d/0B6SfMAw6tfpRX0xXV0pSOW9xSEk/view?usp=sharing

I also took a video of the MIP0227SY test just in case I did it wrong!


I was thinking if I couldn't fix this, maybe there would be a way to use a standard PC Power Supply to handle the job of this board? I would probably need to confirm the job of this PCB first though!

If anybody can think of anything to try next, that would be great!

Thanks :-o

[mswhin63]

The MIP0227SY is a fully contained switching regulator that includes a FET. The biggest problem is that you cannot test it easily using a multimeter except the source drain which appears low. In nearly all the switching supplies that I have repaired most required replacing the switching FET or Transistor. I actually have one on my bench now that blew the switcher. The ease of an external switching regulator is that you can test the FET or Transistor easily.

Although overall there looks to be some modifications that look a bit suss, so treat it with care. If you can get the board number, see if you can source another board just in case.

[KJDS]

Somewhere on that board will be the clue you need to buy a replacement module.

[s34n]

Great, thanks for the help! I will try and source something similar, its from a very old japanese arcade machine so it's not something i ca source officially easily.

I really want to find out the job of this board and see if I can replace it's functionality with a standard PC power supply if you can tell easily what it does? I think it outputs +/-5v

[mswhin63]

Hi, There are a couple of tell tale signs, although not overly clear. It appears it is variable output to 94V (NOTE 94V - 0 written on the output connector) also the output filter caps are rated to 10uF 100V, although the video is not overly clear on that as the video was too high to see the values on the cap. Looking at the datasheet the output Vds is rated up to 650V so I am sure 3V is a bit low for its purposed specs. Being a switching regulator a multimeter is not entirely the best measurement device. An isolated oscilloscope would best see the switching waveform.

I believe it is only a single output supply voltage as there is only 1 output stage that I can see.

That is about the best I can see at this stage, and maybe completely out on this.

[KJDS]

Hi, There are a couple of tell tale signs, although not overly clear. It appears it is variable output to 94V (NOTE 94V - 0 written on the output connector) also the output filter caps are rated to 10uF 100V, although the video is not overly clear on that as the video was too high to see the values on the cap. Looking at the datasheet the output Vds is rated up to 650V so I am sure 3V is a bit low for its purposed specs. Being a switching regulator a multimeter is not entirely the best measurement device. An isolated oscilloscope would best see the switching waveform.

I believe it is only a single output supply voltage as there is only 1 output stage that I can see.

That is about the best I can see at this stage, and maybe completely out on this.

I'd put a reasonable stack of money that the 94V-0 refers to it's UL rating

[Shock]

Somewhere on that board will be the clue you need to buy a replacement module.

I saw it as well. It's for a 240v input.

So unless it's been successfully/properly modded or can be reversed back to original you aren't getting far with this one.

[KJDS]

It's definitely a single output power supply, that much is obvious from the underside of the board. If you can trace the wiring onto the board that it supplies then you could see if it goes to any 74 series logic. If it connects to pin 14 of a 14 pin 74 series chip then it's definitely 5V. Then  just source a 5V open frame power module of similar size and a decent power rating.

[lightman]

Hi
It is single 5V power supply, you can tell for the voltage rating of the output capacitors and the traces, I will bet it is something between 5 and 10 Amps.

if you have a lab power supply program it with 5A if not enough go up slowly up to 10A, if you don't well... a series 8-10A fuse and  a computer power supply on 5V line (most cheap computer PSUs regulates over the 5V line so you would be OK just loading 5V) but since it can deliver a LOT more current than you need, a series fuse could be a good idea, because you don't know if this is the only problem.

the polarity is easy as well just follow the big capacitors traces.
I really wouldn't lost any time with this (well may be replace the IC power switcher, but not beyond that) just purchase a standard 5V 5 to 8A switching brick and  you are done!.

[s34n]

Hi There,

Thank you all so much for the responses! I must admit the responses are a little over my head, but I would like to either attempt repairing the Transistor/bridge rectifier (If these are cheap enough to replace), or replace the board completely. I don't mind a little work if the cost is marginally different.

Are you able to link me to something that may work in it's place? There are a lot of options on eBay and amazon that I think may work, but you suggested the amppage may need to be adjusted to make sure enough current is provided?

That being said, I do have 2 PC PSU's that are sitting in a closet that I wouldn't mind using if at all possible.

I don't know if it helps, but I think the output from this PCB powers a game board via JAMMA

Thank you

[nadona]

...
That being said, I do have 2 PC PSU's that are sitting in a closet that I wouldn't mind using if at all possible.
...

Try it.

[helius]

I saw it as well. It's for a 240v input.

I missed where it says that...
you can't go by '250V 3A' as that seems to be the spec for the fuse. 250V is the isolation standard for line fuses worldwide.

[s34n]

Hi,

Sorry for delay in the update.

I never managed to fix the power supply board, I have no idea what the issue was, I replaced a lot of components on that board and the fuse kept blowing!

I did confirm that the board has a 120v input and outputs 5v, so I used a standard PC power supply and jumped the on-button pins so it auto-starts, and just connected the 5v line from the molex cable to the end of this complete power supply.

So hurray it works! I'm not sure if anybody will ever have this same issue, but if they do, this was my very bad workaround.

Thanks for the help