Tektronix 2225 Channels showing up twice - Page 1
Forum section: electronics / beginners

author: elore
author_rank: Newbie
timestamp: March 10, 2019, 06:05:13 am
content: 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.

author: macboy
author_rank: Super Contributor
timestamp: March 10, 2019, 01:03:03 pm
content: 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.

author: bd139
author_rank: Super Contributor
timestamp: March 10, 2019, 01:12:20 pm
content: 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.

author: elore
author_rank: Newbie
timestamp: March 10, 2019, 04:22:59 pm
content: 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

author: bd139
author_rank: Super Contributor
timestamp: March 10, 2019, 04:55:12 pm
content: Cool. Glad it worked

author: David Hess
author_rank: Super Contributor
timestamp: March 10, 2019, 06:01:10 pm
content: 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 (!), Magnification2215/2215A/2235 Alternate Dual Delayed, Magnification2236/2236A Alternate Delta Dual Delayed, Magnification2220/2221/2221A Single, Magnification2225 Single, Alternate Magnification2201/2205/2210/2211 Single, Magnification465/464/466 Mixed Dual Delayed, Magnification475/475A Mixed Dual Delayed, Magnification485 Alternate Dual Delayed, Magnification465B/468 Alternate Dual Delayed, MagnificationMany of the various 465 models also optionally support Alternate Delta Dual Delayed.Single delayed is like having a 1.5 delayed sweep.