SMPS

davebms · Post by **davebms** » Fri Jul 26, 2013 8:06 pm

hello all i have 2, 24 volt smps to try on gk-71 the got bashed and broken in the post.. but i got a refund so they are free

there is a coil
that i think is an inductor ? they got snaped off but i have soldered them back in place the snag is they get very hot 20 mins and the hot melt glue that i used to hold them in place melts the rest of the thing seems ok

should that part get that hot

Paul Barker · Post by **Paul Barker** » Fri Jul 26, 2013 8:25 pm

Probably ok you wouldn't normally use hot melt glue in an ambient cooled smps. Tie wrap.

davebms · Post by **davebms** » Fri Jul 26, 2013 8:52 pm

Paul Barker wrote:Probably ok you wouldn't normally use hot melt glue in an ambient cooled smps. Tie wrap.

thank for the reply i only used hot melt to hold them in position
so i could solder them back in place,, they got bashed so hard that
it snaped the wires to these things 1.3mm dia solid copper.. smps are rated at 10 amps 24volts,, seems odd that that other parts that have heat sinks are realy cool,, and this coil thing gets to hot t touch in 20 mins

IslandPink · Post by **IslandPink** » Fri Jul 26, 2013 9:31 pm

Wow !
Another GK71 heated by SMPS . Seems to be all the rage at the moment.
I'm wondering which part it was that came adrift, Dave - you didn't label it on the picture .
There are a couple of inductors, a transformer and at least one CMC in those those circuits - which I can see in your photo . Any clues ? if it's 1.3mm copper, I'm wondering if it's a 10A CMC on the output ?

davebms · Post by **davebms** » Fri Jul 26, 2013 9:40 pm

IslandPink wrote:Wow !
Another GK71 heated by SMPS . Seems to be all the rage at the moment.
I'm wondering which part it was that came adrift, Dave - you didn't label it on the picture .
There are a couple of inductors, a transformer and at least one CMC in those those circuits - which I can see in your photo . Any clues ? if it's 1.3mm copper, I'm wondering if it's a 10A CMC on the output ?

its the large open looking coil thing,, sort off behind the red out put lead.

its near the output

Paul Barker · Post by **Paul Barker** » Fri Jul 26, 2013 11:05 pm

Perhaps an inductor used to set the frequency so you could alter the oscilation frequency within reason by changing the number of turns, less turns higher frequency.

IslandPink · Post by **IslandPink** » Sat Jul 27, 2013 12:03 pm

So, it's behind the red output leads if your head is on the right , facing the unit ?

If it's the open coil thing with wire visible ( half surrounded by small electrolytic caps ) then I'd say it's a common mode choke (CMC) , used to get rid of some of the HF noise before it goes out of the circuit .
It's a bit surprising it's so hot, but I don't know enough about how hard they run these parts in SMPS's .
It's quite a tall, heavy object , not surprised it was vulnerable to vibration in transit .

I think the frequency is set much earlier in the circuit, it would be near the transformer, Paul , via a chip of some sort. If it's anything like the laptop SMPSs, they can sense the input voltage , and adjust frequency and ( particularly ) pulse-width, before it enters the transformer .

How are you dropping the voltage down to get 20V ?

Paul Barker · Post by **Paul Barker** » Sat Jul 27, 2013 3:38 pm

You're probably right.

davebms · Post by **davebms** » Sat Jul 27, 2013 9:06 pm

How are you dropping the voltage down to get 20V ?[/quote]

this smps has an adjuster that works fine

its deffo a CMC connects to the + side of the out puts (they are all connected, in-side so no need to parallel the out puts) i dont think much can be done

its supost to be 10 amp 120watts

is it possable to make a dummy load insted of a GK-71 so i can run it for longer ?

pre65 · Post by **pre65** » Sat Jul 27, 2013 9:19 pm

davebms wrote:
is it possable to make a dummy load insted of a GK-71 so i can run it for longer ?

Use ohms law to work out a resistor value.

Work out the wattage and use at least double.

EDIT.

20v @ 3A = 6.8R (nearest standard value) and 61.2W

I suppose a 100W resistor might do for testing IF IT WAS ON A HEATSINK !!!! (without a heatsink it's only rated at 50W)

http://www.ebay.co.uk/itm/100W-Aluminiu ... 1e74cec73b

shane · Post by **shane** » Sat Jul 27, 2013 9:39 pm

How about two 12v 20w lightbulbs in series?

IslandPink · Post by **IslandPink** » Sat Jul 27, 2013 10:02 pm

Should be OK, but lower wattage - if you can find something around 22R with 40 or 50W rating, than you can parallel that with the lightbulbs and get closer to the real load.

Why are you concerned about running the GK-71 'for longer' ?

IslandPink · Post by **IslandPink** » Mon Jul 29, 2013 7:42 pm

Worth mentioning here, as well as the GK-71 thread, that a Dell 90W laptop SMPS ( 19.5V 4.62A ) goes into current protection & doesn't work, when connected to a cold GK-71 .

davebms · Post by **davebms** » Mon Jul 29, 2013 8:18 pm

http://www.ebay.co.uk/itm/300913220196? ... 1497.l2649

this is what i have, i think it may be ok, i have run it for 1 hr the CMC
gets up to 70 deg, im going to try a small fan to pull a bit of air round it

but its not small

IslandPink · Post by **IslandPink** » Mon Jul 29, 2013 8:29 pm

That's a beast Dave. Certainly man enough for the job ;
but on the other GK-71 thread -

http://www.audio-talk.co.uk/phpBB2/view ... c&start=45

I've found a Sony 19.5V / 5.1A laptop supply is just enough and surprisingly quiet as far as line & radiated noise goes .
See eg. -
http://www.ebay.co.uk/sch/i.html?_odkw= ... 4&_sacat=0

audio-talk

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