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Jim Yanik
 
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"Luca T." wrote in
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Hello,
i have a HP 1740A. Unfortunately it stopped working while it was showing
the 1V calibration signal and i was changing the VOLT/DIV scale to
increase its size on the screen.
The screen stopped showing the signal and also i noticed that it is not
anymore illuminated (changing the scale illumination doesn't change
anything).
I opened it and i can see that the cathodic tube shows an orange light
and its brightness changes when i change the "scale illumination" but
the screen keeps being "black" [without illumination].

Any idea about what might cause this?

I checked all the Test Points where i could read the supposed voltage
and all seems fine, unfortunately i do not have a service manual (i
believe this is how you call those manuals for reparation purposes) so i
could not test many other test points.

Does anyone have the service manual for this oscilloscope and could send
it to me by email?

Thank you,
~ Luca

P.S.: Sorry for my bad english.


Basic modules of any scope;
1. power supplies;*first to be checked*
2. vertical deflection circuits
3. triggering
4. sweep(horizontal) deflection
5. CRT unblanking and intensity control

If you can access the vertical and horizontal deflection CRT pins,you can
short them (vert-vert,H to H) and see if you get a trace or spot on screen.
If so,then you have a problem in the corresponding circuit.(short verticals
and get trace=bad vertical amp).short horizontal pins and get spot=bad
horiz or triggering)

--
Jim Yanik
jyanik
at
kua.net