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Old 1st Dec 2020, 1:49 pm   #1
ekcopyephilips
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Default (2s)k2544

Hi All

Im attempting to repair a SMPS for a piece of analytical equipment, it has a K2544 fitted that is dead short. Its an N channel Mosfet 80w.

Please can someone tell me where i can get one of these or what a suitable equivalent would be.

The failure mode was quite odd, the heatsink it was on is very rough (almost like sandpaper) and a sharp spike has punched through the rubber insulator shorting it out. Made quite the bang when it failed.

Kind Regards

Mike
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Old 1st Dec 2020, 2:30 pm   #2
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Default Re: (2s)k2544

None at the usual mainstream suppliers, RS, Farnell, etc.

There are quite a few listed on the usual auction sites at the moment but you can never be sure of their provenance from those sources. I would tend to trust the ones being sold from the USA or Germany more than the ones coming out of China, but of course they are the more expensive examples so it will depend on whether you are spending someone else's money or your own.

There seem to be a mixture of conventional devices with exposed metal tab and also ones with plastic 'shrouded' TABs as well.
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Old 1st Dec 2020, 2:44 pm   #3
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Default Re: (2s)k2544

Hi Mike,

The "alltransistors" web-site list 62 equivalents to the 2SK2544:
https://alltransistors.com/mosfet/tr...ansistor=14397
Just click on the "Equivalent Substitute" link.

You can also enter the critical MOS FET parameters into the parametric search engines that most of the part suppliers have on their web-page.

Regards, Peter
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Old 1st Dec 2020, 4:30 pm   #4
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Default Re: (2s)k2544

600V 6A mains switcher, quite generic. Maybe something like P60NB6 or similar.
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Old 1st Dec 2020, 5:06 pm   #5
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Default Re: (2s)k2544

It's worth also checking the gate turn on voltage spec in case the original part is one intended for low gate drive. If you fit one with a higher threshold the device doesn't get turned on to low resistance and the dissipation will cause a burn-up.

David
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Old 1st Dec 2020, 5:32 pm   #6
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Default Re: (2s)k2544

Just to add to the burden, with such a catastrophic failure of insulation and a big bang, all that current had to pass through something: Like the mains input rectifiers for example, or the primary winding of the main transformer, if it is that sort of SMPSU.

Have you had a good look around to see if this failure event took out anything else? You wouldn't want an overlooked secondary fault to damage your brand new FET, should you manage to lay hands on one.
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Old 1st Dec 2020, 5:45 pm   #7
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Default Re: (2s)k2544

They usually blow the source resistor and the driver chip through the gate.
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Old 1st Dec 2020, 9:33 pm   #8
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Default Re: (2s)k2544

Oh dear that doesn’t sound great. I’ll try and take some pictures tomorrow. I have no cct diagram of the PSU either.

Thanks for all the reply’s

Mike
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Old 2nd Dec 2020, 8:10 pm   #9
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Default Re: (2s)k2544

In this case, you might be in luck, since the drain shorted to ground externally. I'd even think the FET could have survived this.
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Old 3rd Dec 2020, 8:12 am   #10
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Default Re: (2s)k2544

I've come across this device and may even still have one, pulled out of an old ATX PC PSU. As others have said am pretty sure a generic fet like the IRF830 will do. I'll see if I have one though. Dropus a PM in a day or so if I haven't responded.

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Old 4th Dec 2020, 4:12 pm   #11
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Default Re: (2s)k2544

Hi All

Thanks for the replys, ive added a few pics so you can see the PCB. I have some additional information too that might help:

It looks like the 240v is fed through a basic filter to a bridge rectifier then a reservoir capacitor.

Pin 1 (Gate) is connected directly to pin 5 of the sub PCB
Pin 2 (Drain) is fed via 2x 1N5397 diodes in parallel from the positive of the reservoir cap (the diodes are the 'wrong' way round) these measure ok.
Pin 3 (Source) is fed via 2x resistors in parallel (1 ohm and 0.5 ohm) to the negative of the reservoir capacitor.

Does this extra info help on choosing an equivalent?

Kind Regards

Mike
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Old 4th Dec 2020, 4:31 pm   #12
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Default Re: (2s)k2544

The style of that PCB looks familiar. Is it an off-the-shelf supply from the likes of Astek?

David
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Old 11th Dec 2020, 7:21 pm   #13
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Default Re: (2s)k2544

Hi all

I forgot to put up a pic of the model number and output of this power supply, finding a FET has proved elusive and I don’t want to use a non approved equivalent because the equipment would be used in a public building.

So, what is this type of psu called so that I can at least try and search for a new one with the same outputs

Kind regards

Mike
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Old 11th Dec 2020, 10:06 pm   #14
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Default Re: (2s)k2544

It's called Phihong (brand name) PSA4534 (model number).

If substituting the transistor is out of the question, you should also only use the same make and model supply or another one approved by the equipment vendor. You could try searching for the brand name and model number of the equipment, with the words "power supply" added, if you don't find a Phihong PSA4534.
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Old 11th Dec 2020, 10:39 pm   #15
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Default Re: (2s)k2544

Have a look at this unit from RS:

https://uk.rs-online.com/web/p/embed...-smps/1830127/

The specification is almost identical to your obsolete one, including the dimensions according to the data sheets.

Worth a look?

Whilst I would always be happy to repair a SMPS, sometimes with these complex units it just isn't worth the hassle, particularly if they have gone bang.
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Old 14th Dec 2020, 10:52 am   #16
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Default Re: (2s)k2544

It's an industry standard "brick" available from many uk sources, I worked in a lab for many years and the equipment was usually run 24/7, the usual failure mode was the reservoir caps. We had a firm that repaired them, but in later years it wasn't worth it.I remember buying a batch of ten for one piece of kit, and kept them on the shelf, they were only £47 each from Farnell, and they had the metal case too.
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Old 14th Dec 2020, 11:12 am   #17
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Default Re: (2s)k2544

I agree, toss it in the bin and fit a new one, just check the pinout of the output header.
I see plenty of Phihong psus, mainly in PC AT form. They're at the better end of the chinese brands but I dont repair those either.
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Old 14th Dec 2020, 12:42 pm   #18
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Default Re: (2s)k2544

You might want to check the condition of the Molex KK (type) connector, I've found three that have gone high resistance on the higher current supplies, they are only single sided contact, the housings go brown sometimes, not good if it's a common 0v pin.
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Old 1st Jan 2021, 5:02 pm   #19
ekcopyephilips
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Default Re: (2s)k2544

Hi all

Just an update, the power supply suggested by agardiner was ordered and fitted yesterday. The pin outs were luckily the same on both supplies. Switched on and it all worked. So thank you so much for your help in getting this going again. The manager of the lab where the equipment lives is very pleased.

Kind regards

Mike
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