[Test-Equipment] HP equip questions

[Dave Brown]

Since Stan has brought the matter up-
snip-
> 5x10E-11. Does this mean that an HP 5245 with a retrofitted 10544A
> timebase should be called an HP 5245H? (or would that be an HP 5245N?)
snip-
Has anyone actually done this type of changeout to a 5245M? And documented
any measurable performance changes?
I use my 5245M as a local freq. standard, but am aware that I could probably
do better these days. Basic question is whether it is worth it or not.

 It's worth noting that the 5245M has an auxiliary psu that runs the time
base continuously as long as it is plugged into AC power. I had a pass
transistor fail in this psu a few years back and it let the nomally
regulated output go high and semi-fry the oscillator/oven assy. I put some
big well over-rated transistors in that psu and one or two extra safety
features as well!

Because I had to pull the ovened assy to bits to replace burned phenolic
insulation pieces and change out a signal buffer transistor (totally
diabolical job-just like a 3d jigsaw puzzle!) I have been a bit concerned
that something similar could happen again.  'Replacing' it with an external
10544A or better on a battery backed supply etc. seems like a good thing to
do. But would be interesting to hear if anyone else has done this sort of
thing to an 'M'.
For the record  a GPS 'stabilising' scheme is in the works for this
reference oscillator, regardless of  what hardware I wind up using.

73 Dave, ZL3FJ