Oscilloscope trace disappears question - Page 1
Forum section: electronics / beginners

author: n0b
author_rank: Contributor
timestamp: December 31, 2015, 03:43:17 am
content: I saw an oscilloscope on Ebay that said that the trace came up then disappeared. What could some possible problems be? How exspensive could the fix be?ThanksBaron ClarkP.SHere is what they said:When turned on, a wave appears on the screen for a split second, then disappears. But I'm assuming it needs to be connected to something(then later)Other then that, I can't really say much more about the unit as I don't even really know what they are used for

author: Brumby
author_rank: Unknown
timestamp: December 31, 2015, 03:50:32 am
content: From the description, it could be anything from a functional scope with an improper trigger setting to something awkward and/or expensive.Is it a CRO or DSO? A make and model number would be helpful - plus a video showing the behaviour.Much more information is required to even start speculating.

author: n0b
author_rank: Contributor
timestamp: December 31, 2015, 03:56:32 am
content: I'm not sure about the video part, I say it on ebay. It is a Tektronix 2213a, analog.And thanks for the reply

author: tautech
author_rank: Super Contributor
timestamp: December 31, 2015, 04:28:40 am
content: If the CRO has the correct settings to display a trace and only does so on power up/down, IME it will be due to a HV or plate output stage problem, the trace momentarily appears as the voltages pass through the normal operating voltage ranges.There'll be plenty of members able to help you fix it if you can get it cheap enough, definitely pay less than $50

author: Brumby
author_rank: Unknown
timestamp: December 31, 2015, 04:48:36 am
content: This one, I take it?http://www.ebay.com/itm/Tektronix-2213A-60MHz-Oscilloscope-/231798635124?hash=item35f8467a74:g:PokAAOSwUdlWhB0NThe fact that it does power on andsomethingappears on the screen is encouraging - to a point. It does suggest taking a punt might be worth the risk, so long as you don't bid too much. Remember, there are working units on offer from around the $200 mark.Since it still has several days to go, I might ask the seller if he could take a video of the unit during power up so you (we) can see what is happening on the screen. This may not prove to be conclusive, but I expect it will show something we can make better guesses about - maybe even thattautechpicked it in one.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 31, 2015, 05:39:39 am
content: If that's the one,checking the pix against an online manual,it seems to be in "auto" with the trigger coupling set to dc,so it should be showing a line on the screen.I would agree, with the others--only if it isverycheap,it may be worth it.

author: n0b
author_rank: Contributor
timestamp: December 31, 2015, 05:45:35 am
content: Thanks so much guys! I will watch it and bid, and if I do end up getting it I will have a thread about fixing the problem.Thanks againBaron Clark

author: alsetalokin4017
author_rank: Super Contributor
timestamp: December 31, 2015, 06:54:16 am
content: Quote from: vk6zgo on December 31, 2015, 05:39:39 amBut it also has the CH1 vertical position knob all the way to one side, which would take the trace off the screen -- and in fact would produce the reported behaviour when the scope is turned on (I just tried it on my 2213a). But the vertical mode switch is set to CH2... so who knows.I've seen a lot of "broken" scopes that were perfectly OK, the owner-seller just didn't know how to set them up to display a trace properly.I see that the V/div indicator skirt on the CH1 knob is broken and about 1/3 of it is missing. This is pretty common; and these knobs are hard to find.http://www.sphere.bc.ca/test/tek-parts/tek-knobs.html

author: vk6zgo
author_rank: Super Contributor
timestamp: December 31, 2015, 07:57:29 am
content: The crazy thing about Oscilloscopes which "don't work",or the vendor "doesn't know whether they work",is that they often attract so many bids that they end up costing more than you would expect to pay for a functional one.http://www.ebay.com.au/itm/oscilloscope-Tektronix-TDS210-model-/281894814810?hash=item41a23d845a:g:TrIAAOSwYaFWe14C

author: Mephitus
author_rank: Regular Contributor
timestamp: December 31, 2015, 10:57:49 pm
content: Or this one:http://www.ebay.com/itm/Tektronix-Analog-Oscilloscope-455-/231771804872I bet that some minor repair and this thing would be good to go. I have a Tek 465 and it's very easy to service.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: December 31, 2015, 11:25:48 pm
content: For certain values of "easy".....