Alberto, In the commercial world that the Z3815A's (and quite possibly the Z3801 etc) were used in, they were installed "vertically" at the bottom of a large equipment cabinet that had convection air channels running within it. A bank of 12-16 fans towards the top of the cabinet sucked up ambient air and forced it past the PA heatsinks. The hot air was vented out the PA modules & cabinet top. Ambient air temp was controlled at 20-25 deg C. The GPSDO pcb (and associated electronics) was cooled with incoming ambient air with the pcb and IC temperatures settling at some value. The critical point here is that the whole cabinet was operating 24x365 and for years on end.
While semiconductor life is inversely proportional (?) to Tamb and cooling the electronics may seem a logical approach to prolonging life, I would suggest that <in this application>, this is a second-order effect. The killer is thermal cycling which can induce premature failure in any electronic assembly - passive or active - with everything else being equal. Most (if not all) of these commerciall modules were designed with very high MTBF's in mind when used "au natural". I would leave well alone and look into providing "standby power" to your Z3801. Regards, Kit VK2LL ************* Message: 3 Date: Mon, 28 Jul 2008 15:40:40 +0200 From: Alberto di Bene <[EMAIL PROTECTED]> Subject: Re: [time-nuts] A fan for the Z3801A To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Murray, thanks for the advice. Well, my intention was, as suggested by a private message, to use a 12V fan powered at 5V, so that it runs slowly and silently, not blowing external air into the unit, but just extracting the hot air from the inside. And given that the unit is placed in the basement of the house, with a change in temperature between the day and the night of no more than 1 Celsius, may be the use of the fan should not disturb the thermal regulation of the OCXO and the other temperature-sensitive devices, while at the same time lowering the working temperature of those hot ICs, thus prolonging (maybe) their life. Anyway I am open to comments and suggestions. Thanks 73 Alberto I2PHD -- _______________________________________________ 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.