On 7/14/05, Mark Chauvin wrote: > I'm experiencing about a 3% failure rate on my PIC-based product. Are you so kind and tell us on how many pieces has been computed this 3%. I'm very curious because I found a quite similar rate in other circumstances. Except > for one time that a wire was cut, the rest of the time it's been the 20MHz > crystal that's died. I'm using a 16C58B chip and the crystal is an Abracon > ABL-20.000MHZ-B2. Is this a normal failure rate for this type of crystal? > Also, I'm not sure what the two capacitors should be. Right now, I'm using > 33pF capacitors with the crystal, but from what I read in the PIC manual > that may not be right. The PIC manual recommends 15pF, but there's a note > that it should be 30pF if VDD > 4.5 (I'm using a 78L05 so VDD is 5 volts), > and Abracon lists "Shunt capacitance" for this crystal at 7pF & "Load > Capacitance" at 18pF. Being almost totally ignorant of circuit design, I'm > not sure what the right capacitors are, so I'm blindly using what someone > else told me to use, but could using a capacitor that's too big cause these > failures? It could be possible that failure comes from the PIC-XTAL resonant circuitry and not from the crystal itself. Do a check by inspecting the shape of your XTAL-OUT pin using a scope and at least 1:10 (verified) probe. Check the signal level for the faulty crystals. Check it again for a good crystal. A too small capacitor on the OSCOUT will reveal a high Vpeak to peak signal, looking like a square signal with some resonant shapes on every high logic level, immediately near every rising edge. A too high capacitor will create a smaller amplitude, looking more like a sinusoidal shape. Essential is the level of that signal. There is some signal with faulty crystals or there is no oscillation ? Answering this will show you who is quilty. best regards, Vasile -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist