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Electronics => Beginners => Topic started by: Mr. Robot on August 29, 2017, 08:43:36 am

Title: Suggestions for power supply for mobile/laptop repair
Post by: Mr. Robot on August 29, 2017, 08:43:36 am

Hi

I do basic mobile and laptop repair for friends, like replacing ports, screens and such. I'd like to go a bit further and practice with logic board repair.

I'd like to get a power supply in order to detect shorted components by injecting current to the board the find the heat source.

Is there a specific type of power supply that is needed for this kind of task? Any suggestion on a particular model?

Thanks

Title: Re: Suggestions for power supply for mobile/laptop repair
Post by: Cliff Matthews on August 30, 2017, 12:29:59 am

Welcome y bienvenido! Response for most questions would not have such delay.. Perhaps Mr. Robot as a screen name was not the best choice.. Folks around here like to help out humans. On the other hand, it could also be an error to assume short circuits cause higher levels of heat than normal. I think this may be what you are after, so check here (http://www.nutsvolts.com/blog/post/build_an_audible_milliohmmeter).

For info on using this technique for finding some faults, you could watch some videos like this (https://www.youtube.com/watch?v=z5JXm9jgLp8) or these (https://www.youtube.com/results?search_query=finding+PCB+shorts).

Title: Re: Suggestions for power supply for mobile/laptop repair
Post by: Mr. Robot on August 30, 2017, 07:23:15 am

Hola Cliff

Thanks for your answer and your links. I'm definitely a human, or at least that is what my mum says :)

I'll had a look at those links. In any case, do you believe that there is a need for a special kind of power supply?

Cheers

Title: Re: Suggestions for power supply for mobile/laptop repair
Post by: Cliff Matthews on August 30, 2017, 11:33:17 am

I wouldn't call it a power supply, it's a current source passing known current through low resistance areas until the lowest is found by measuring minuscule voltage drops. I'm not a fan of this method and I wouldn't go poking around in 3.3v logic areas around expensive QFP's without verifying pinout's first. A few times I've tried cutting traces on power rails to isolate areas to measure changes in Vcc, but on a laptop, no way if it's not mine.
There's a board level guy called Louis Rossmann, who has a few videos:
https://www.youtube.com/results?search_query=louis+rossmann+finding+shorts (https://www.youtube.com/results?search_query=louis+rossmann+finding+shorts)
Since you mentioned heat, this one in particular may help:
https://youtu.be/t5fICjcaJ3E  (https://youtu.be/t5fICjcaJ3E)