Tektronix 2215 with short trace

[David Hess]

A common failure which can cause a slightly short sweep is the JFET used to buffer the sweep integrator, but I would determine if the problem is the sweep generator or horizontal CRT amplifier first since that can be done externally in XY mode.

[bdunham7]

One thing you can check if it hasn't been mentioned is the horizontal sweep rate.  Make sure the cal knob is locked and set the horizontal to 1us/div and apply a 1MHz signal (or whatever combination works for you that would give 1 cycle per division).  Then check and see if your cycles are squeezed to less than a division, in which case the sweep is compressed, or if the cycles are approximately 1 per division, in which case it is truncated.  If compressed you probably have a horizontal gain issue, if it is truncated, a sweep generator issue.  If it is 9 divisions long, it is possible that some clown has gone in there before you and diddled the adjustments to hell--so you might start with the calibration and adjustment part of the manual. 

[BrianHansell]

May I thank both bdunham7 and David Hess for your replies. I appologise for the delay in replying but I have been away from home and therefore done no work to this baby.

David, as far as XY is concerned, a base line trace gives just a dot that can be moved off of both edges of the screen, so this would signify a Sweep Generator problem as opposed to the Horizontal CRT amplifier.

When I was playing with it I noticed that a Baseline trace set to five seconds/division (I do like things when they're slow) gave a momentary miniscule flash of the beam as it passed each division line. This could be repeated for both the one and two seconds per division, so the timing circuits seem to be ok.

Once again thanks gentlemen, I will now go and put your theories to the test. " I'll be back ".

regards

[David Hess]

That does seem like a problem with the sweep generator, which is hardly unknown with these oscilloscopes.

Sometimes the JFET which buffers the integrating capacitor fails with high leakage leading to problems like you describe.