Say, anybody know any disadvantages of using
freeze spray as a duster or a duster as freeze spray?? Turn one
upside-down to make it work as the other, of course.? TIA.
Jim Ford
Sent from
my T-Mobile 4G LTE Device
-------- Original message --------
Date: 3/1/22 12:12 PM (GMT-08:00)
Subject: Re: [HP-Agilent-Keysight-equipment] HP8640B RF
Fails Several Seconds After Power Up
@Jim: I too am a big fan of freeze spray. It can really root
out faults that would otherwise be very difficult to diagnose
with bench equipment, especially intermittent issues like this.
I gave each of the regulator sections a nice dose of freeze
spray, without any revealing results, except for the one
drawback of such techniques, namely the condensation that can
result after cooling the boards, which in this case would throw
the regulators off until they'd dried off. Ordinarily, I avoid
freezing entire sections of a circuit at once, preferring to
freeze each component separately with a nice steady and directed
drip from the freeze can. This not only helps eliminate the
condensation issue, but saves on the freeze spray, which is not
inconsequentially pricy. Unfortunately, without any extender
cards, it's nearly impossible to just freeze a specific
component at a time, so, firehose freeze spray it is! Anyway, it
didn't expose any temperature sensitive issues on the regulator
cards.
@George: I definitely plan to re-flow all of the TO3
connections, and clean the sockets and pins. Even if it doesn't
fix this issue, it's good hardware hygiene in any case. I'll put
all of the power transistors on a curve tracer too, and run them
through a wide temperature sweep. None of them generated any
notable heat while in circuit, but a flakey P/N junction can
decide to fail at relative room temperatures. I will say, the
day this failed, the temperature in my shop (uninsulated barn
actually) was probably in the mid 40°s, F. Admittedly a silly
temperature to be aligning a receiver, but it was intended to be
a rough alignment. I was bored, what can I say?
@Dave: As long as I've had this 8640, is has always been
positioned horizontally, so I would hope this would preclude the
possibility of the lubricant creeping into the electronics. I do
agree that the behavior of the 44.6V supply floating high when
the oscillation stops, seems like the regulator's reaction to
being underloaded, perhaps when the circuits it supplies, take a
nap. Thanks for the tips on where these los might reside.?
I really need to make or buy some 15 pin extender cards.
Troubleshooting such circuits without, is like trying to fish
coins out of a storm drain. Anyone know a good source of such,
that aren't priced by concert scalpers?
