[time-nuts] Defective Z3801 and strange PS board

[Marco IK1ODO]

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