[time-nuts] HP Z3801a insights and progress.
paulswedb at gmail.com
Sat Dec 17 15:59:10 EST 2016
Making serious progress on the ole basket case Z3801a.
Somethings that may be helpful to others.
Its easy to completely remove the 48 volt power supply and use a normal
bench supply. Especially if you are not using the outer oven and have a bad
ocxo. So all below without the ocxo and a TBolt 10 MHz feeding the 3801 ref
Red +5 at 57 ma
Yellow + 15 at 27 ma
Blue -15 at 0 amps very small.
The purple is a control wire and the green is a temp sense from the outer
Seems not to matter on these two. Though I sense (Pun intended) green does
need to be set.
How does the system tell when the OCXO is warm. Since the OCXO gets 24
volts by a +/- 12 V the sense must go negative to at least -9V.
this then signals the oven is warm. The rest of the 3801 starts working.
I suspect this same require can be used for the outer oven. Its unclear its
By using an external bench supply the board becomes easy to work on after
the 48 V converter is taken off. This is a great way to troubleshoot.
More to learn.
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