gbusg at comcast.net
Sat Oct 10 23:03:04 UTC 2009
I think 1 o'clock (instead of 12 o'clock) might still be OK and/or typical?
Maybe some other 5370A users can tell us where their Trigger Level pots are
pointing when centered for triggering on a weak signal. (The pots point to
12 o'clock on my 5370B, but I can't remember exactly where they might point
on a typical "A".)
I do know that some of the 5370A A3/A4 Input Amp & Schmitt Trigger I.C.s
developed "I.C. rot" many years after manufacture (due to a contamination
problem during manufacture). For units so afflicted, the symptom was that
"Preset" trigger level was no longer correct, but the trigger level could
still be successfully set manually. For these cases, as the years progressed
(and the "rot" worsened), you had to turn the manual trigger level pot
further and further to one direction to find trigger. As the years of
deterioration continued, there came a point where both trigger level
setability and sensitivity were no longer acceptable.
If you have only a small trigger level issue in "Preset" mode, my thinking
is that you can still correct for it by doing the A3/A4 input adjustments.
----- Original Message -----
From: "Joseph Gray" <jgray at zianet.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Saturday, October 10, 2009 2:23 PM
Subject: Re: [time-nuts] 5370A
Yes, the trigger levels are near zero when the LEDs are flashing. The
level pots are both at 1 o'clock, instead of 12 o'clock, however.
There does seem to be a problem with the preset trigger postition.
Although the display shows 0.00V when at preset, I don't think it is.
When I manually set the levels to 0.00V, the TI shows 100nS. At preset
levels, the TI is noticeably higher.
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