Locating short circuits with bnch psu

[scobie_21]

Re: Locating short circuits with bnch psu

I think maybe this is just a crap PSU heres the link to the exact model
http://www.gotronik.pl/zasilacze/pxn1505.html

[scobie_21]

Re: Locating short circuits with bnch psu

Would anybody have a manual for this or similar unit ? Also is the C.C led on the current supposed to be on all the time ?. The C.V led is always off on the Voltage. Could this unit be faulty I only bought it this week?

[Th3_uN1Qu3]

Re: Locating short circuits with bnch psu

C.C. light on means it's current limiting. Are you sure you have set the current limit correctly? It should only go on when you short the output, or apply a load in excess of what the PSU can provide. With an open circuit output, the C.C. led should never come on, instead the C.V. one should be lit.

We have the same power supplies in the lab at uni and they work just fine, maybe you got a dodgy one. You may have to return it.

[scobie_21]

Re: Locating short circuits with bnch psu

C.C. light on means it's current limiting. Are you sure you have set the current limit correctly? It should only go on when you short the output, or apply a load in excess of what the PSU can provide. With an open circuit output, the C.C. led should never come on, instead the C.V. one should be lit.

We have the same power supplies in the lab at uni and they work just fine, maybe you got a dodgy one. You may have to return it.

Yeah I think you are right about it being faulty. When its switched on it automatically shows red C.C led and if you try adjust it just stays 0.00 if you short out the leads both voltage and current go to 0.00 and the C.C led turns green. You then have to turn off the psu before it will do anything else.

[tom66]

Re: Locating short circuits with bnch psu

To set the current on most lab power supplies short the output terminals.

Reminds me of my lab lecturer freaking out when I did this trying to set the current. He said it would blow the fuse. It didn't, it is how you do it (set the voltage lower so you don't get a spark from the capacitor on the supply's output but otherwise there shouldn't be an issue.)

[scobie_21]

Re: Locating short circuits with bnch psu

To set the current on most lab power supplies short the output terminals.

Reminds me of my lab lecturer freaking out when I did this trying to set the current. He said it would blow the fuse. It didn't, it is how you do it (set the voltage lower so you don't get a spark from the capacitor on the supply's output but otherwise there shouldn't be an issue.)

Yeah but that's the problem as well there is no way of adjusting the current it doesn't respond to adjustment when shorted. If you connect to dc motor and increase voltage it will showing the change of current but theres no way of controlling it.

[smason]

Re: Locating short circuits with bnch psu

Definitely broken.

Take it apart, might be something simple like a loose wire, bad solder joint, you might get lucky.

[rievax_60]

Re: Locating short circuits with bnch psu

When you say you try to stay under .5A how do you control this ? I don't seem to have any current limit on my supply It just goes straight to protection mode and I have to switch of the bench psu then on again so theres no chance to find components heating up.

I start at zero volts then increase it gradually. If the shorted component has a very low resistance like below 0.1 ohm, its difficult to make it heat up noticeably.
I use the millivolts range on my multimeter to find the area on the rail with the lowest voltage reading. My meter only has 100uv resolution, so its not much good for finding a short on a power plane.
I have found that shorted surface mount ceramic capacitors change resistance slightly when heated with a soldering iron.

[aspire550z]

Re: Locating short circuits with bnch psu

for a cheap and reliable psu i think this may be a good buy....http://www.attenelectronics.com/Prod.../0728/104.html i use it since 7..8..month ago without any problem...apart from noisy cooling fan..(i had replaced it with new)..btw..i'm not from atten...

[sasser]

Re: Locating short circuits with bnch psu

with bench PSU also we know current input. almost below 5A. if current got 1.000A above some issues with bga power. anyone agree with my theory ?

[popeye]

Re: Locating short circuits with bnch psu

When using bench power supply to fault find short set current limit to0.5A @1V to start if there is a short componants should heat up after a while you can increase the voltage but not too high as if one of the supply mosfets or regulators are short if you find south or north bridge getting hot switch off imeadiately or you may end up putting 19v through one of the bridges or CPU
the machine would then be scrap.

[sasser]

Re: Locating short circuits with bnch psu

popeye u mean slowly up the volt from setting 5A with 1v ? then up the volt till getting hot? i always set actual volt 19.5v then see the current come in.

[fddizon]

Re: Locating short circuits with bnch psu

181188333005 this might find you interested...

sasser, popeye is right. that is the way

[ben7]

Re: Locating short circuits with bnch psu

C.C. light on means it's current limiting. Are you sure you have set the current limit correctly? It should only go on when you short the output, or apply a load in excess of what the PSU can provide. With an open circuit output, the C.C. led should never come on, instead the C.V. one should be lit.

We have the same power supplies in the lab at uni and they work just fine, maybe you got a dodgy one. You may have to return it.

An EE friend of mine wanted me to get a 'proper' bench psu, but I am still hesitant, because of all the crappy, cheap chinese ones on ebay! XD

[popeye]

Re: Locating short circuits with bnch psu

popeye u mean slowly up the volt from setting 5A with 1v ? then up the volt till getting hot? i always set actual volt 19.5v then see the current come in.

Hi


the setting for current is 500mil amp half of an amp any more and you risk damaging the board beyond repair. this setting is only for when you have a short circuit before the voltage goes from KBC.

[sasser]

Re: Locating short circuits with bnch psu

popeye just double confirm to set adjustable psu with start 1v and 0.500A how about if the laptop in s5 need fully loaded 19v? or u mean just only 1v is enough to see either mosfet or regulator hot?