Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!think!snorkelwacker!mit-eddie!uw-beaver!milton!whit From: whit@milton.acs.washington.edu (John Whitmore) Newsgroups: sci.electronics Subject: Re: Slowing down a disk drive Summary: ceramic resonator, similar to quartz crystal Keywords: 350 rpm -> 300 rpm Message-ID: <1717@milton.acs.washington.edu> Date: 3 Feb 90 02:39:07 GMT References: <324@ctycal.UUCP> Reply-To: whit@milton.acs.washington.edu (John Whitmore) Organization: University of Washington, Seattle Lines: 28 (Terry Ingoldsby writes: >indicated an oscillator that seems to be controlled by a >small, green, square edged device on the printed circuit >board, about .7 cm wide, .3 cm thick and .5 cm high. The >device appears to be a ceramic capacitor EXCEPT for the >fact that all other caps on the board are silk-screened as >C1, C4, etc. and this one is called Y01. Well, you have definitely found the frequency-setting component. It is a crystal resonator made of a polycrystalline material (ceramic), and "poled" into the correct behavior by electrical biasing while it was being boiled in oil... Such ceramic resonators, and the similar ceramic filters, are cheaper than quartz crystals, and more than accurate enough for most applications. The "Y01" is a crystal designation, and I guess the ceramic components are close enough to qualify. Usually a replacement for such a component would be a "pi" network; input node to capacitor to ground and to an inductor, other end of inductor to capacitor to ground, and to the output. Replacing the inductor with a quartz crystal, this becomes a parallel resonant crystal circuit. If you want to change the value, find capacitors and an inductor such that 1/SQRT(L * C) = 2*pi* where 1/C= 1/C1 + 1/C2 for the two capacitors Depending on the nature of the resonator, it may have external capacitors already connected in the appropriate spot. Good luck. I am known for my brilliance, John Whitmore by those who do not know me well.