Hi guys
I want to expand the range of repairs I can undertake. Currently I'm mostly fixing TVs, Audio equipment, DJ Equipment and 'disco' lighting. Having said that I have fixed a couple of SATA hard drive controller boards
I would like to offer repairs of Laptops. Tablet PCs, motherboards etc
I currently have a couple of faulty MAG250 IPTV boxes here
Both of these have short circuits (or low resistances) on one voltage rail or another (3.3V / vCore)
On one of them, using my bench PSU in CC mode and applying voltage to the 3.3V rail with the buck regulator inductor removed, I gradually ramped up the current to see what would getting warm. At the full 3A (V was now about 2V or so) the only thing getting warm is the big (STi7105-BUD) BGA chip on the centre of the board.
The other one has a short/fault on the vCore rail - I managed to get the 3.3V up to the correct voltage but with about 2.5A flowing - which is too much - and again only the STi7105 was getting hot. The oscillator was even running, but nothing else seemed to happen.
I decided I would have a go at removing one of these BGA chips with the hot air station just to see if that was really the cause of the low resistance but to be honest I couldn't even get it to come loose with any reasonable amount of heat applied. Also there are a lot of smd components on the other side of the pcb below the STi7105 and I was worried they may fall off with too much heat
However what I did notice, once the board had cooled back down is the 12 ohm low resistance on the 3.3V rail is now about 7 ohm so that has changed by heating the chip.
Out of interest I googled the STi7105-BUD and found a couple of interesting things.
http://www.alldatasheet.com/datasheet-pdf/pdf/244196/STMICROELECTRONICS/STI7105.htmlFirstly it does not seem to be a programmable device but uses external Eeprom/Flash
Secondly I can get them for 7.50 euros inc postage
Sooooooooo....... I was thinking of having a go at fixing them, as much for the learning experience as anything else, and of course the ability to take on more similar repairs
Getting parts is not the problem. Question is - what equipment and techniques would I need to replace this type of chip?
Assuming I can get the BGA chip off without breaking something, how do I get the replacement one positioned correctly to resolder?
I've watched youtube videos a-plenty of BGA reballing/resoldering but to be honest I am now more confused than when I started
Obviously you need the right tool for the right job - What investment in equipment would I have to make to be able to repair these sort of faults with an acceptable level of success?
Pics of the STi7105 BGA and the underside of the MAG250 board showing the components beneath it. This would be a good example of the type of repair I would like to undertake so let's start with that.
Cheers
Rich