Hack Correlation

I was scoping around to see what caused the 2.5V supply modules to go bust. Just as a reminder, they are pretty generic modules, with a 5V preregulator that steps down the 12V input. The 5V is then dropped through linear regulators to three supply rails of 1.8V, 2.5V and 3.3V. In this application only the 2.5V output is being used.

I just bought a cheap broken DVR from eBay and thought to share pictures from inside the unit since there aren't any on the Internet. It was a state of the art unit at the beginning of 2000, probably costing several thousands of dollars. Some documents and review from that time praise the wavelet-type encoding quality and savings, custom-made ATX power supply and build quality. I beg to differ on a few fronts.

I've gotten two DVR MPEG4 recorders for free because they were labeled as "unfixable". Both of them were diagnosed with "no video" or "video problems".  Ever since I've had them I had suspected the 2.5V supply to be at fault but had no oscilloscope nor variable PSU at hand, so they have been sitting in my drawer for a few months. It was a 10 minute job: - probe the 2.5V output and see it oscillating between 2.4 and 4.2V - probe the PAL/AV output and see the scope could not get a lock even though it looked almost ok - bypass the supply and feed 2.5V from a variable PSU - probe and do a quick run to see everything is stable. I wish I could do a burn test but my trusty variable PSU is a linear one, getting quite hot at this voltage drop.