Originally Posted by Floydage
I would think Sony MTBF-analyzed the crud out of their designs.
I have seen some examples that don't support that idea, i.e. common failure modes after several years of operation based on type of product.
This IC issue on CRT HDTVs is one example of a common failure.
A friend had a convergence problem on his Sony rear projector TV. Web searching indicated that this was a common symptom/problem caused by failed video amplifiers. Risked $50 for replacement amp modules, and the repair was successful.
I have a Sony ES surround sound pre/pro unit that has had power supply issues. A web site dedicated to this unit mentioned this common failure, and prescribes replacement of a few opto-isolators for repair. The first repair was good for a few years, but a second repair lasted only a few weeks before the unit failed (w/the same symptoms) for the third time. There's something that's overloading this power circuit.
Professionally I've only worked with MIL-SPEC or at least industrial-grade electronics. Those units use components that are de-rated; components are operated well below their stated limits of temperature, dissipated power, voltage, etc.
These Sony units are consumer-grade electronics. I assume that manufactured cost control is job #1, and components do not get de-rated.
How many years out should a MTBF analysis go for consumer-grade electronics? Five years seems generous when there's only a one-year warranty.
But such an analysis is only as good as your assumptions.
Do you account for dust buildup on the PCBs that will increase heat retention?
Do you account for installation in a media cabinet that will increase operating temperature?
Maybe you design & build for the worst case so that MTBF is more than the warranty period.
But shortened lifespans of a few years or 10000 hours for overstressed components operating in harsh conditions would probably be acceptable to a manufacturer of consumer-grade stuff. It's pretty rare to find products that are "overbuilt" or "built like a tank" (unless you go to a high-end audio/AV shoppe).
The common failures indicate that some products have weak points that IMO are likely caused by operating at or near component specs. There's nothing in the pattern of failures that seems to disprove this generalization/hypothesis.
RegardsEdited by blue_z - 8/5/13 at 7:17pm