Tektronix 2225 Channels showing up twice

[elore]

Hello all, I am new to the forum and to hobbyist electronics. Recently I picked up an older analog  oscilloscope to learn the basics on from ebay but I noticed something odd. The scope is a Tektronix 2225 and everything seems to be in order. I checked the knobs and buttons and they all seem to be working (as far as I can tell) but the channel signals show up twice. When I adjust the position knobs they move in pairs as if it is only one signal that is being doubled. When I adjust the seconds/division knob to the slower settings the signals appear to move slowly as expected but the duplicates appear to move a bit faster in comparison. This is the only difference I could tell between the two. The scope has not been calibrated for over a decade. I do not know if that has anything to do with it but I thought I’d share everything I know.

I attached a photo of what I mean. Both channels are on but the upper two lines are from channel 1 and the second two are from channel 2. Any input is appreciated thank you.

[macboy]

This is a dual (or delayed) timebase scope and you have that feature enabled. Turning this off may be as simple as pushing the horizontal timebase knob in (pull to enable). I do strongly encourage you to read about this feature in the manual, as it is a very powerful and desirable feature.

[bd139]

2225 doesn’t have delayed timebase. It has mag instead. Above the timebase control switch it to X1 instead of alt and it will go away.

Nice scopes.

[elore]

I switched it to X1 instead pf ALT just like you said bd139 and it went away! I thought I got a dud there for a second! Shows I still have a lot to learn about oscilloscopes. Now I can start learning

[bd139]

Cool. Glad it worked 

[David Hess]

In my notes I refer to this feature as "alternate magnification".  When magnification is active, the magnified traces are displayed alternately with the main traces.  It is basically a poor man's alternate delayed sweep which is distinct from delayed sweep and mixed delayed sweep.  Alternate magnification was very rare or unique to the 2225.

2213/2213A   Single Delayed (!), Magnification
2215/2215A/2235   Alternate Dual Delayed, Magnification
2236/2236A   Alternate Delta Dual Delayed, Magnification
2220/2221/2221A   Single, Magnification

2225   Single, Alternate Magnification
2201/2205/2210/2211   Single, Magnification

465/464/466   Mixed Dual Delayed, Magnification
475/475A   Mixed Dual Delayed, Magnification
485   Alternate Dual Delayed, Magnification
465B/468   Alternate Dual Delayed, Magnification

Many of the various 465 models also optionally support Alternate Delta Dual Delayed.

Single delayed is like having a 1.5 delayed sweep.