Hello boss, how are u? I think everybody is fine. Today i need your help. I think you will be help me how to use lab power supply to find short on laptop motherboard. Pls Share youre knowledge with us and keep update our service line... Thank you.
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Re: How to use lab power supply
If you apply voltage across very low resistance then the result must be many amps.
I apply low voltage (depending on the rail - 1V is mostly enough) and limit the current to 1A and touch by hand, if nothing heats up then it is time to add more amps. If the short is inside a big IC (northbride or smth), then even 3A might turn it only slightly warm. If you give too much amps at once and the short is inside a small cap, then it might burn up and you might get damaged pcb.
The main point is that you don't need to use high voltage to find shorts.
I attach the negative lead with alligator clip to ground and for positive lead i use either a alligator clip with needle or if more amps are needed then soldering is required. I used rather thick wire (~2mm diam) to solder the alligator clips to, because if you don't then the wires are going to heat up instead. If any questions - ask and will try to answer -
Re: How to use lab power supply
I am not clear about positive lead connection. negative lead connect with pcb ground? and positive lead use with needle. I m not understand what is needle. pls give me an example, how to connect positive lead for finding 3.3v rail short. please clear me. Many many thanks for reply. wait for reply.Last edited by nazrul145; 04-16-2014, 10:25 PM.Comment
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Re: How to use lab power supply
Needle is a really thin tip. When using many amps you DON'T want to touch the metal, I use a multimeter tip, it's thin enough and provides you some plastic protection..
One little tip to add, when seeing or feeling heat wasn't working for me, I spread some solder paste around the area, applied current, and the capacitor started bubbling at the bottom almost immediately.
Good luck!Last edited by Learn2Day; 04-16-2014, 11:41 PM.Galaxy S6 Edge x2 (Gold&White)
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Vizio e601i-A3 - Has Sound and Display, But No Backlight - Bad Power Supply Board or Bad LED Bulbs ?I was given this TV from my great uncle. He said it just wouldn't turn on one day out of nowhere, replaced the TV, and gave it to me to possibly fix and use for myself.
Upon bringing it home and plugging it up, it showed a standby light.
I powered it on and without a flashlight, the display showed the "V" but the lighting is very dim, but visible.
The screen seems to blackout and stay black, but with a flashlight I can see the display.
With my Playstation 4 connected via HDMI, and running a game I can hear sound.
Assuming... -
I have been working on this concept for quite some time now with limited success but recently I found a switching power supply that is setup for the voltage that this soldering station needs to operate at however it also needs part of the secondary circuit from the original switching power because you need several voltage rails
I once tried to get a ZD-915 desoldering station to work on a 18 volt battery power supply but unfortunately things did not go well but I did find a work around but I might try this idea again but going at a little differently more about this another time... -
The LM358 LM358S-13 consists of two independent, high gain, internally frequency compensated operational amplifiers which were designed specifically to operate from a single power supply over a wide range of voltages. Operation from split power supplies is also possible and the low power supply current drain is independent of the magnitude of the power supply voltage.
Application areas include transducer amplifiers, dc gain blocks and all the conventional op amp circuits which now can be more easily implemented in single power supply systems. For example, the LM358 series can be directly...10-07-2024, 04:12 AM -
HP ENVY x360 - 15-dr1017tx
i have these board which when turn on power lights on but amps volt is 000 -
The sub developed a constant popping every couple seconds from woofer and power LED flickering with nothing but wall AC connected. Connecting an audio cable didn't change anything. It doesn't play but a second or two of audio in between the pops.
Opened it up and discovered the power supply is making a faint clicking or ticking sound.
I measured the amp's output to the woofer and it pulses up to 50mv DC to be driver. The pulses coincide with the power supply ticking/clicking.
I measured the power supply output going to the amp board and it too has this pulsing. Voltage cycles...
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