Oscilloscope adjustment...width

redrabbit · 21st November 2008, 02:19 AM

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 ?).

=RR=

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.

CY

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.

see http://www.sphere.bc.ca/test/tek-par...ing-scopes.pdf

redrabbit · 21st November 2008, 03:41 AM

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.

=RR=

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.

21st November 2008, 02:19 AM	#1
redrabbit diyAudio Member Join Date: Oct 2004	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 ?). =RR=

21st November 2008, 03:41 AM	#3
infinia diyAudio Member Join Date: May 2005 Location: Californication	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 __________________ like four million tons of hydrogen exploding on the sun like the whisper of the termites building castles in the dust

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21st November 2008, 03:20 AM	#2
CY diyAudio Member Join Date: Nov 2002 Location: Hong Kong	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

21st November 2008, 04:41 AM	#5
CY diyAudio Member Join Date: Nov 2002 Location: Hong Kong	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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