Author Topic: atx psu is ticking won't provide constant power [Solved]  (Read 1629 times)

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Offline DeadSk8er

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atx psu is ticking won't provide constant power [Solved]
« on: April 22, 2015, 12:50:52 pm »
right so I've build a power supply from an old atx psu, but now it started making this ticking noise like a clock.
It had some bad caps I replaced, but the ticking is still there can't really find anything else that looks bad.
oh yeah also when I connect a led to it, it blinks at the same interval as the ticking noise
any advice on what it could be?

it's a super flower psu Model NO: SF-400P14P
« Last Edit: April 25, 2015, 09:26:52 pm by DeadSk8er »
 

Offline Grapsus

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Re: atx psu is ticking won't provide constant power
« Reply #1 on: April 22, 2015, 12:59:28 pm »
Please explain us the what you modified in the PSU. Was it working before the mod ?

Ticking may be an overcurrent condition or bad mains filtering caps or another more subtle problem.
 

Offline DeadSk8er

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Re: atx psu is ticking won't provide constant power
« Reply #2 on: April 22, 2015, 01:08:58 pm »
I'm not 100% sure if it was, was running fine on old pc and I never noticed the ticking left it standing for about 4 months without powering it up
all I did was seperate all the different voltage rails so basicly I took all the 12v, 5v and 3.3v so I got all the different voltages on different outputs and the ground of course
added a 5w 22ohm dummy load between a 5v and gnd. and replaced all the bad caps. as far as I was able to see
also placed a switch between the gnd and the power on cable
« Last Edit: April 22, 2015, 01:20:27 pm by DeadSk8er »
 

Offline marinedalek

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Re: atx psu is ticking won't provide constant power
« Reply #3 on: April 22, 2015, 09:30:54 pm »
Sounds like typical PC PSU behaviour when running on too small a load. Try a car bulb on the 12V rail to see if it becomes steady. If it does, you need to experiment and find the minimum current draw.
 

Offline T3sl4co1l

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Re: atx psu is ticking won't provide constant power
« Reply #4 on: April 22, 2015, 10:09:35 pm »
You didn't put the load resistor on the standby 5V supply, did you?

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline DeadSk8er

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Re: atx psu is ticking won't provide constant power
« Reply #5 on: April 25, 2015, 09:26:21 pm »
thx for the advice I'll try the bigger load some other time..
I worked on it for hours couldn't figure it out
think my fluke multimeter is fucked or something aswell..
anyways ended up grabbing one of my other old psu's I had laying around,
had it working in 20 mins so now I got a lab power supply that works,
again thx for the help.
 

Offline retiredcaps

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Re: atx psu is ticking won't provide constant power [Solved]
« Reply #6 on: April 25, 2015, 09:46:44 pm »
A number of suggestions.

1) If you only replaced the obviously bloated capacitors, there may be more capacitors that are bad, but require out of circuit testing with an ESR meter.

2) Ticking suggests the SMPS is trying to start, but can't because
a) the startup capacitor (generally 22uF to 47uF/25 to 50V) is bad due to high ESR
b) the SMPS IC is bad
c) there is something shorted on the secondary side like a diode

3) If you think your Fluke meter is not working properly, start a new thread and I will try to provide suggestions on what to check.
 


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