The cheap PC supply may need a load greater than the Thunderbolt to work, as a quick dirty hack I've used a 12V auto signal light on the 5 volt supply.   Stanley ----- Original Message ---- From: Didier Juges <didier@cox.net> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Sent: Saturday, June 14, 2008 8:31:22 AM Subject: Re: [time-nuts] [Fwd: Re: Thunderbolt PS] > > I would like to add an extra question: > > > > How about adding an extra filter after a cheap PC power supply? > > > > 73, > > > > Rainer > > > >  > Whilst that may help with the high frequency power supply > noise, it wont help with power supply flicker noise. > > Bruce Or the lousy regulation and temperature stability, which on a cheap supply may be worse. If the cheap supply can be adjusted to provide 6V instead of 5 and 14V instead of 12, both outputs could be followed by a stable low drop-out voltage regulator (probably discrete rather than an IC) to provide stable and clean 5V and 12V respectively. The -12V only drives the RS-232 chip I believe, so I don't think there is anything to gain with further regulation. If the voltage is too high (as a result of adjusting the other outputs), use a cheap regulator or a zener/resistor. Didier _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.