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Old 21st November 2008, 01:19 AM   #1
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Default Oscilloscope adjustment...width

I installed a used projection tube in a miniature oscilloscope (VU Data), to replace the original tube that broke (cracked).

It works, except that the trace is shrunk horizontally--the trace does not extend to the sides, like it should.
External adjustments do not fix this...so ...
What internal adjustment might I find inside the unit ??... (Like a trim pot or trim cap maybe ?).

Click the image to open in full size.

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Old 21st November 2008, 02:20 AM   #2
CY is offline CY
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I do not quite understand the "projection tube'".

If I am faced with such a problem with my scope, I would try to adjust the gain of the X amplifier which amplify the horizontal sweep signal and could stretch out the display horizontally.

I suppose you may need to identify the X amplifier board and look for some trim pots.

CY
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Old 21st November 2008, 02:41 AM   #3
infinia is offline infinia  United States
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Cy is correct
Locate the horizontal amplifier s/b connected to CRT deflection.
Find gain adjustment pot.\X-Y position front panel still works/
May need to check timebase accuracy.

see http://www.sphere.bc.ca/test/tek-par...ing-scopes.pdf
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Old 21st November 2008, 02:41 AM   #4
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Quote:
Originally posted by CY
I do not quite understand the "projection tube'".
CY
Sorry, should have said, "Cathode Ray Tube".


I'm reading that guide (pdf link) now.
Thanks guys.

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Old 21st November 2008, 03:41 AM   #5
CY is offline CY
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Did you replace the tube with one of the same model?? If not, there is a good chance that the sensitivity of the new tube being lesser than the old one hence causing the problem.

You may have the same problem with your Y amplifier without you noticing it. You may also need to tune up the amplification of your Y amplifier.
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