Mr. Smith, IF I understand that the TR50 and DTVPal are identical in design then my observations in my ONE repair(my unit-DTVPal), I can state that there IS an LSI
chip on the main motherboard, under the front left metal shield/cover. A quote from Wikipedia "Further development, driven by the same economic factors, led to "large-scale integration" (LSI) in the mid-1970s, with tens of thousands of transistors per chip."
The way an integrated circuit is mounted is dependant on the number of circuits that is contained inside the chip itself. The multitude of connections that these LSI chips need to communicate to the other devices circuitry require a different method to solder via small balls to the circuit board pads. BGA (Ball Grid Array). Regarding the bulging tops on capacitors, I would be remiss if I
performed a repair without replacing any cap I saw that had a bulging top, even thought its function was not associated with the reported problem. Although these "bulgers" may still function properly, you will have to agree that they ARE on the way to failure and their replacement would be mandatory for a proper service repair... I hope in your 50+ repairs that you DID replace ANY cap that was bulging... Even though you may have measured/tested them as "good"... I have attached two jpg's one of a TYPICAL BGA chip, in this case an Intel chip and another that does show an LSI chip that is used in the DTVPal, (front left).... Again the link for the LSI chip used in the DTVPal is : http://www.alldatasheet.com/datashee...S/STI7109.html
A block diagram attached shows that there is a ton of functions that this LSI chip provides..
Your assessment of the cause of BGA failure is quite accurate and proper. Even slight printed circuit board flexing will be detrimental to the mounting of thee chips...
That's my story and I'm sticking to it.. :-)
I still know a good optometrist :-)