Repaired my Tektronix 2225 but 4 lines?? What the - Page 1
Forum section: electronics / repair

author: marty
author_rank: Contributor
timestamp: March 01, 2016, 09:47:52 am
content: First I want to say this is my first repair, first scope, second lab piece of equipment I suppose since I had a semi-decent multimeter, first desolder, first solder, so I am a NOOOB.I got this Tektronix 2225 wouldn't power on. Took me all day to fix it and the power rails are all within spec. the only thing I found out of alignment so far was the trace rotation, and I can't do much more yet until my frequency counter shows up then I can build my Oscillator. Oh and my probes wont be here for another 4 days.I get ch1 and looks like a 2nd line, same goes for ch2.It doesn't do this on anything else rest seems like normalI watched Dave's videos and recreated what his did and his didn't show 4 lines but when I look at the manual fold out it seems to show 4 lines and the first picture on the manual.this normal?Here's settingsTriggermode p-p/autosource ch 1 line ac coupleVerticalch1/ Div doesn't matterch2/ Div doesn't matterch1 acch2 acHorizontalhold off doesn't matterAlt Div doesn't matterX-5

author: tautech
author_rank: Super Contributor
timestamp: March 01, 2016, 11:21:22 am
content: QuoteThis would imply you've set the triggering toLine, this means the scope will trigger at your mains line frequency. This is fine for when needed, but that is not often. Turn Line triggering off.For most use you'll want the trigger DC coupled, change that too.X5 s/div multiplier should be off too.With a CRO you need think about the signals you are intending to see, they're not at all like a DSO where you can just hit the Autoset button and it sorts it all out for you. You do have to "drive" a CRO.First sanity check is the probe Cal output, they're mostly 1 KHz frequency and square wave and at a few volts, commonly 3 or 5V. So now set the vertical to 1V/div and the timebase to 1ms/div and your ready to check the probe Cal output with a 1:1 probe. Remember a 10x (10:1) probe will divide the signal by 10 so to see the same amplitude waveform as you've just set up for, the vertical would need to be changed to 100mV/div.Got your head around all that?So have a play with a piece of wire in the BNC and your probe Cal output, but nothing else until your probes arrive.Again, think about the settings you'll make before anything's connected, probably Trigger settings are the most important.Take the time to watch some of Alan's vids on scope use in the sticky thread in the Beginners forum.Enjoy.

author: wkb
author_rank: Super Contributor
timestamp: March 01, 2016, 11:27:16 am
content: Quote from: marty on March 01, 2016, 09:47:52 amEhmm.. any chance you can post some pictures of what you observe? This is a bit hard to follow (at least it is to me)

author: siggi
author_rank: Regular Contributor
timestamp: March 01, 2016, 03:15:32 pm
content: Quote from: marty on March 01, 2016, 09:47:52 amCongrats on the repair!Quote from: marty on March 01, 2016, 09:47:52 amIt looks like the 2225 has a magnified sweep in addition to the regular sweep.If the horizontal MODE button is set to ALT, you should see both normal and magnified traces, for a total four traces (Vertical MODE set to BOTH and ALT or CHOP).With horizontal MODE set to X1 or ALT modes you should see only two - is that what you observe?With an input signal on the channels it'll be clearer what's happening - DC isn't very interesting to magnify neither in vertical nor horizontal.

author: marty
author_rank: Contributor
timestamp: March 01, 2016, 03:57:19 pm
content: great thanks, I just wasn't sure if something else was broken after seeing Dave's video of him messing with his, I thought I had some issue.Quote from: tautech on March 01, 2016, 11:21:22 am

author: marty
author_rank: Contributor
timestamp: March 01, 2016, 04:30:33 pm
content: Thanks yes it's that alt mode that's showing the 4 linesQuote from: siggi on March 01, 2016, 03:15:32 pm

author: marty
author_rank: Contributor
timestamp: March 01, 2016, 04:46:33 pm
content: Quote from: wkb on March 01, 2016, 11:27:16 am

author: LazyJack
author_rank: Frequent Contributor
timestamp: March 01, 2016, 06:17:45 pm
content: Yeah. You are switching the horizontal magnification on and off. As said here before, alt displays the normal and the magnified trace simultaneously, so four traces for two channels. Hook up the calibrator to the input, you'll immediately see it. Also, reading the manual really helps, this switch is explained there on page 2-2.

author: Milmat1
author_rank: Contributor
timestamp: March 04, 2016, 02:43:11 pm
content: Quote from: LazyJack on March 01, 2016, 06:17:45 pmExactly, As you (OP) will discover as you learn to use this scope, This is a very handy feature.. I have a 2225 as well, and it is good scope...