| Author |
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Luca T.
Guest
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 Posted:
Thu Feb 10, 2005 10:01 pm Post subject:
Oscilloscope HP 1740A, how to fix it? |
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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.
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Jim Yanik
Guest
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| Posted:
Fri Feb 11, 2005 6:11 am Post subject:
Re: Oscilloscope HP 1740A, how to fix it? |
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|
"Luca T." <lucat@despammed.com> wrote in
news:371eqdF582vqjU1@individual.net:
| Quote: | -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
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 |
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Luca T.
Guest
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| Posted:
Sat Feb 12, 2005 2:58 pm Post subject:
Re: Oscilloscope HP 1740A, how to fix it? |
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Jim Yanik wrote:
| Basic modules of any scope;
| 1. power supplies;*first to be checked*
This seems to work, at least the values that i could read on some
test-points were correct, unfortunately i do not have a service manual
or anything that would tell me what the correct voltages of other
test-points are (i could only test the ones where their supposed voltage
values is written on the board).
| 2. vertical deflection circuits
| 3. triggering
| 4. sweep(horizontal) deflection
| 5. CRT unblanking and intensity control
|
Sigh, i am absolutely ignorant about oscilloscopes and without a manual
to tell me exactly what to do i am lost :(
| 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)
|
I wish i knew where those pins are, i do not really feel like to
short-circuit random pins. Sigh... anyone knows where i could find the
service manual of this oscilloscope without having to buy a copy?
Thank you for your answers,
~ Luca
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