I have a Motorola based 5 MHz unit, that's a rack mount, that's the same, using a 45-48 Vdc supply, and was told at the time it was due to the Telco standard voltage. I use it with my Racal products, as their timebase is at 5 MHz. By the way, this unit was pulled from a cell tower.
Best, Will *********** REPLY SEPARATOR *********** On 7/9/2011 at 11:19 AM bownes wrote: >My educated guess is that they expected to sell these to telcos, who traditionally run everything in a central office on -48v and running off of ac was an afterthought. > > > >On Jul 9, 2011, at 9:43, Marco IK1ODO <ik1...@spin-it.com> wrote: > >> Hello group, >> >> after many years (about 12, I think) of faithful continuous operation, my Z3801 failed. >> I opened it, and found that there was no supply to the main PCB. The power supply board in the Z3801 (and Z3805, 58503A, possibly all the series) is marked 58503-60003. It is a very strange board. It seems to have a first DC-DC converter taking 48V input, powering two other DC-DCs that work on 48V (!), one supplying +5/+15/-15V to the main board, the other supplying 5V 4A to a fourth DC-DC that drives the outer oven with up to 18V. >> Well, it is the first DC-DC that failed. I bypassed it, powering directly the no. 2 and 3 from 48V, and all works again. The questions are: does a schematic for that board exist? Anyone knows why such a complex power supply architecture was adopted? It is not very energy-efficient, all those DC-DC run hot. >> >> 73 - Marco IK1ODO / AI4YF >> >> >> _______________________________________________ >> 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. > >_______________________________________________ >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. > >__________ Information from ESET Smart Security, version of virus signature database 5851 (20110206) __________ > >The message was checked by ESET Smart Security. > >http://www.eset.com _______________________________________________ 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.