[time-nuts] Re: Z3801A questions

[Mahlon Haunschild]

Yeah, you guys are thinking like I’m thinking.  I really don’t feel like
spending time sorting out the power supply when all I really need to do is
pull the two DC-DC converters and connect up my triple supply.

Btw, one converter is +-15VDC, 830 mA and +5V 5A (25W total combined) the
other one is +5V 4A.

Best regards

Mahlon - N4ZK

On Sat, May 20, 2023 at 12:17 PM paul swed <paulswedb at gmail.com> wrote:

> Mahlon I am aware that the big black block that is a DC to DC converter
> does fail.
> So as you suggest absolutely just replace it with a AC to DC multiple
> output unit. Think it was +12 -12 +5. But the schematics and such show what
> the voltages are.
> The other thing is the input circuit to the unit can also fail. Its all
> pretty reasonable to troubleshoot or get rid of if you do not intend to run
> on batteries. My Z3801 has never been run on batteries. Though I have 2 X
> 24 V linear supplies in series for it. Been working fine for 15 years or
> more. I am knocking on wood right now.
> Regards
> Paul
> WB8TSL
>
> On Sat, May 20, 2023 at 11:42 AM Bob Camp via time-nuts <
> time-nuts at lists.febo.com> wrote:
>
>> Hi
>>
>> First step would be to look for melted blobs / debris where capacitors
>> used to be …..
>>
>> Bob
>>
>> > On May 19, 2023, at 9:17 PM, Mahlon Haunschild via time-nuts <
>> time-nuts at lists.febo.com> wrote:
>> >
>> > Hello list.  Just joined and, after reading the list archives, I feel
>> that I Am Not Worthy to ask these questions, but here goes.
>> >
>> > I’ve had a Z3801A just sitting around for years now and, the other day,
>> I finally decided to experiment with it a bit.  I already had a 26dB Andrew
>> antenna and a Vicor 48V 2.9A power supply for it, so I put the antenna on
>> the back of the receiver with some N adapters, wired up a serial cable to
>> an ancient ThinkPad running SatStat, placed the whole rig in the back yard,
>> and turned everything on.
>> >
>> > To my astonishment, after placing it into survey mode, four hours
>> later, it had completed its sky search and had switched over into position
>> hold, with a  TFOM of 3 and a FFOM of 0.  Since all I wanted it for was to
>> use as a freq reference, I thought it was good to go.
>> >
>> > The next day I tried it again.  No go.  The Z3801A acted like it had
>> developed an internal power supply short because it was causing the Vicor
>> to go into current limiting, with zero volt output.
>> >
>> > I’ve read the material on 56V vs 48V switching supply startup for
>> these, and I will them that next.  Failing that, I’ll troubleshoot the
>> power supply.
>> >
>> > It appears that a long time ago someone reverse-engineered the power
>> supply design and published a schematic for it, and Google found it
>> somewhere in https://xdevs.com/doc/HP_Agilent_Keysight/ <
>> https://xdevs.com/doc/HP_Agilent_Keysight/> but is it on the web
>> elsewhere?
>> >
>> > If all else fails I’m tempted to yank the two DC-DC converters from the
>> power supply board and power the whole thing with a suitable AC-DC
>> triple-output switcher (specifically, a Nemic Lambda LWT-50H-5FF, which is
>> on hand).  Has anyone done this?
>> >
>> > Lastly, I’m considering trying an Oncore UT+ instead of the VP to get
>> its better front-end filtering.  Opinions?
>> >
>> > Best regards and thanks in advance,
>> >
>> > Mahlon - N4ZK
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