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5370 troubleshooting help needed

Scott Newell
 

My 5370A has never completely worked. It will measure time interval,
especially from stop to start, but frequency and period are way off (10MHz
ref measures as about -97kHz, or about -10.299us). A friend loaned me a
book, but it's a little out of date to my serial number (2044A010XX).
Anyway, I've been going though some of the fault trees, and I think I've
got a problem with the stop channel arming circuit (I suspect it's stuck in
the armed state).

For instance, I can power the sucker up with the inputs set to sep, X1, 50
ohm, positive slope, and no input signals. +TI mode, 1 sample, mean, etc.
If I toggle the *stop* slope, then the start slope, the display will update
and show the interval between stop and start. From what I can tell, this
is wrong in +TI mode. Can anyone check against a known good 5370?

If anyone is following along in the book, I'm working through the A22 fault
tree:

2: Connect BNC cable from rear panel 10MHz output jack to front panel START
input. Set both LEVEL controls to PRESET. Also set switches to 50 ohm,
X1, DC, START COM, SLOPE switches to rising, SAMPLE RATE out of HOLD, and
FREQ STD switch (rear panel) to INT. Turn instrument power on. Counter
should power up to TI, MEAN, SS of 1, and +TI only. -> 3

3: Does counter display ~100ns? No -> 4

4: Remove input signal and push RESET. Does the ARM light come on? Yes -> 6

6: Is U21(12) an EECL low (-0.6V)? Yes -> 8

8: Are P1(/6) and P1(12) at EECL lows (-0.6V)? Yes -> 10 [I think they
mean P1(/12)...]

10: Does level at P1(/6) change to EECL high (0V) when position of start
channel SLOPE switch is changed? (Return to rising when done.) Yes -> 22

22: Push RESET. Is TP10 an EECL high (0V)? No -> 23

23: Flip flop U24A and U25B is not being reset. U25 pins 14 and 15 should
be EECL low (-0.6V). [End of the line, no further direction. U25-14 and
U25-15 are both low, as they should be.]


thanks!
newell N5TNL
John Miles
 

Hi, Scott --

I have a 5370B, but am not sure what differences there were between the -A
and -B models. They are really neat pieces of gear.

I don't understand why you're able to get an interval reading from "stop" to
"start". That is exactly backwards. On mine, I can wiggle the trigger
level adjustment on the "start" channel, then do the same on "stop", and it
will tell me the elapsed time between the two events. If I do it the way
you described, it doesn't trigger.

That makes me wonder if you have either (a) some swapped cable connections
inside, or (b) a source of noise on the Start channel that's allowing it to
complete a sampling cycle.

What I don't understand about mine is the fact that none of the adjustments
on the trigger-level calibration step (A18) can reach -2.56/+2.55V. I
actually have two DAC assemblies, and neither of them will crank past about
+/-2.35V. Voltage at TP4 and TP5 always ends up around +/- 1.9V as the
trigger level controls are adjusted, regardless of what the display says.
It works fine -- the only consequence is a slight reduction in trigger-level
range -- but I've always been curious as to why the DAC output compliance
doesn't seem to achieve spec on either of the two boards I have.

There's some good info on the 5370 at
, for what it's worth. Maybe
the author (John Ackermann) is on the list and will see your inquiry, or you
could email him?

-- john KE5FX

My 5370A has never completely worked. It will measure time interval,
especially from stop to start, but frequency and period are way off (10MHz
ref measures as about -97kHz, or about -10.299us). A friend loaned me a
book, but it's a little out of date to my serial number (2044A010XX).
Anyway, I've been going though some of the fault trees, and I think I've
got a problem with the stop channel arming circuit (I suspect
it's stuck in
the armed state).

For instance, I can power the sucker up with the inputs set to sep, X1, 50
ohm, positive slope, and no input signals. +TI mode, 1 sample, mean, etc.
If I toggle the *stop* slope, then the start slope, the display
will update
and show the interval between stop and start. From what I can tell, this
is wrong in +TI mode. Can anyone check against a known good 5370?

If anyone is following along in the book, I'm working through the
A22 fault
tree:

2: Connect BNC cable from rear panel 10MHz output jack to front
panel START
input. Set both LEVEL controls to PRESET. Also set switches to 50 ohm,
X1, DC, START COM, SLOPE switches to rising, SAMPLE RATE out of HOLD, and
FREQ STD switch (rear panel) to INT. Turn instrument power on. Counter
should power up to TI, MEAN, SS of 1, and +TI only. -> 3

3: Does counter display ~100ns? No -> 4

4: Remove input signal and push RESET. Does the ARM light come
on? Yes -> 6

6: Is U21(12) an EECL low (-0.6V)? Yes -> 8

8: Are P1(/6) and P1(12) at EECL lows (-0.6V)? Yes -> 10 [I think they
mean P1(/12)...]

10: Does level at P1(/6) change to EECL high (0V) when position of start
channel SLOPE switch is changed? (Return to rising when done.) Yes -> 22

22: Push RESET. Is TP10 an EECL high (0V)? No -> 23

23: Flip flop U24A and U25B is not being reset. U25 pins 14 and
15 should
be EECL low (-0.6V). [End of the line, no further direction. U25-14 and
U25-15 are both low, as they should be.]


thanks!
newell N5TNL






Yahoo! Groups Links
Scott Newell
 

At 05:26 PM 8/15/2004 -0700, John Miles wrote:
Hi, Scott --

I have a 5370B, but am not sure what differences there were between the -A
and -B models. They are really neat pieces of gear.
Absolutely. I'm very impressed with the startable phase locked oscillators
used to vernier against the timebase, even though I don't fully understand
how they pulled that off.


I don't understand why you're able to get an interval reading from "stop" to
"start". That is exactly backwards. On mine, I can wiggle the trigger
level adjustment on the "start" channel, then do the same on "stop", and it
will tell me the elapsed time between the two events. If I do it the way
you described, it doesn't trigger.
Thanks so much for taking time to test that. This fits with my guestimate
that the stop channel is armed in +TI when it shouldn't be. (You should be
able to measure negative time from stop to start in +/- TI mode.)


That makes me wonder if you have either (a) some swapped cable connections
inside, or (b) a source of noise on the Start channel that's allowing it to
complete a sampling cycle.
I've been wondering about swapped cable connections too, or maybe something
to do with the HPIB interface (as it can swap the inputs under program
control). If they were swapped, I wouldn't expect the counter to display
the time interval sign correctly. (If I blip stop, then start, the
displayed time interval is negative, as it should be. Start then stop:
displayed time interval is positive.)

Noise on the start channel would start the measurement interval, then
complete the measurement when I blip the stop channel (which would update
the display). In fact, I can blip the stop channel (no display update),
then the start channel (display update).



What I don't understand about mine is the fact that none of the adjustments
on the trigger-level calibration step (A18) can reach -2.56/+2.55V. I
actually have two DAC assemblies, and neither of them will crank past about
+/-2.35V. Voltage at TP4 and TP5 always ends up around +/- 1.9V as the
I'll see what mine is sitting at next time the cover is off.


There's some good info on the 5370 at
, for what it's worth. Maybe
the author (John Ackermann) is on the list and will see your inquiry, or you
could email him?
Yeah, I've pestered him with 5370 questions back before I had a book...and
I thought he might be on this list as well.


thanks!
newell N5TNL

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