[time-nuts] Defective Z3801 and strange PS board

Will Matney xformer at citynet.net
Sat Jul 9 15:32:37 UTC 2011


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 <ik1odo at 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
>> 
>> 
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