The gear train is just a gear train... but, as you point out, in quartz, it is under a lot less stress. Eta's higher end (flatline) quartz are designed to be disassembled and repaired like any of its mechanicals... but it shouldn't need it for a very long time if it is highly jeweled like most are. (Seiko has gotten away with no jewels... but the Japanese don't come from a tradition of long lived movements so probably don't think about this much.)
Originally Posted by Ray MacDonald
The circuitry is really only a quartz crystal and (usually) one integrated circuit module. Quartz crystals are very durable. The single module is a pretty simple one that isn't really state of the art anymore.
The only things that are likely to kill these modules are
1) the random cosmic ray (!) -- a gamma ray can create new conductive paths inside the chip.The other main killer of quartz is destruction of the signal paths on the printed circuit board. The most common reasons for this are
or 2) a strange power surge -- they also cause shorts in the chip. But the only power source is a battery and they tend to loose voltage rather than surge to high voltage.
1) acid leakage from a dead batteryMost manufacturers will just replace a quartz movement with another quartz movement... it's so much cheaper than fixing them. They would probably do this with mechanicals too if they thought they could get away with it.
2) mechanical shock causing distortion of the board (this will probably kill the gear train too)
3) improper repair... 'tourists' can kill anything
But the better quartz movements can be repaired. Check the Eta Technical Documentation for their quartz movements... they even give parts lists, disassembly and assembly instructions. The manufacturing documentation gives electrical tests for the electronic parts.
I have 45 year old computers that still work... the only problem usually is the things that move like disks and cooling fans ... oh, and dirty switches...