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redrabbit 21st November 2008 02:19 AM

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 ...
What internal adjustment might I find inside the unit ??... (Like a trim pot or trim cap maybe ?).


CY 21st November 2008 03:20 AM

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.


infinia 21st November 2008 03:41 AM

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.


redrabbit 21st November 2008 03:41 AM


Originally posted by CY
I do not quite understand the "projection tube'".

Sorry, should have said, "Cathode Ray Tube".

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


CY 21st November 2008 04:41 AM

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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