[time-nuts] "The Penultimate HP5065 A15"

[Poul-Henning Kamp]

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Bob kb8tq writes:

>If a more extensive rebuild is in the works …..

Yes, that's where we're headed eventually, but I prefer to do it
incrementally.

>+/-20V is (as has been observed) not an ideal voltage for “modern” electronics. 
Right, and being able to drop that down later is in the design.

However, from a noise point of view, there is a lot to be said for
having local LDO's on individual subassemblies.

>A11 Unless you want to redo the heater windings on A12, you are
>stuck with +20 to +30V. Rest of the board sort of begs for a modern
>op-amp approach.

I have not given much thought to A11 yet, and I do find a certain
elegance in the wien-bridge approach.  It is worth noting that the
actual heaters run of the unregulated supply, when I stabilized
that, A11 worked less hard.

Unless you plan to run the HP5065 at the freezing point, I expect
the heaters could run of a lower voltage, though +15V may be too low.

>A14 If the upstream boards get changed, this likely does as well.
>Sort of begs for a $1 MCU and a handful of resistors as a replacement. 

I was actually pondering doing that on A17.

-- 
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