First Oscilloscope Advice - Page 1
Forum section: electronics / testgear

author: arrow727
author_rank: Newbie
timestamp: April 04, 2015, 06:17:13 am
content: I've been looking at buying an oscilloscope for some time now and came across this Tektronix 7633 on Craigslist for $115. The guy says it has 4 plug in channels with two 7A18 dual trace amplifiers and a 7B53A time base installed. The display works, shows a clean looking trace in the pics, shows a couple sine waves through it, and he says it's pretty much up to spec comparing it to his function generator. But the storage part doesn't work and the display "tends to flood". Those are my main two concerns with it. My first question is, does anyone know how to fix these problems if possible? My second is do you guys think this is a good deal and if not, are there any suggestions on what I should offer him? I'm looking at it tomorrow and kind of want to be a little more prepared. Here's the link if you want to see the scope I'm talking about:http://detroit.craigslist.org/okl/ele/4897851086.htmlThanks so much for the help in advanced!

author: Rupunzell
author_rank: Frequent Contributor
timestamp: April 04, 2015, 06:41:27 am
content: Storage tube bloom is often due to lack of user knowledge. 7633 has both variable persistence and bistable storage, four storage modes total. To use the variable persistence storage properly, it takes reading the user manual and some experience. 7633 also has reduced scan to increase effective writing speed. The CRT brightness (writing speed) is lower than non-storage CRT's as a trade off for the storage feature. These do not make good daily user due to their specialization and the CRTs die over time by loosing display brightness. This is where a DSO is a better way for most applications that require image retention.Quick search will return the user/service manual.BerniceQuote from: arrow727 on April 04, 2015, 06:17:13 am

author: tautech
author_rank: Super Contributor
timestamp: April 04, 2015, 07:03:02 am
content: Yes, CRO storage scopes use specialized phosphors for waveform retention.These are renown for not lasting as long as conventional phosphors. You might be lucky and the scope has had little use, however if you want to capture and save waveform images, a DSO is THE best option.

author: arrow727
author_rank: Newbie
timestamp: April 04, 2015, 12:40:02 pm
content: So are you guys saying I should pass on this scope? I know Dave has said multiple times in different videos to get an analog scope so that's why I was considering this one.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: April 04, 2015, 08:14:34 pm
content: Quote from: arrow727 on April 04, 2015, 12:40:02 pmDave has also repeatedly said that people should stop taking this old advice from 2009(?) literally, as it's no longer accurate because the entry level scope market has changed a lot from the time he made the recommendation.

author: timofonic
author_rank: Frequent Contributor
timestamp: April 05, 2015, 02:37:12 am
content: Quote from: Wuerstchenhund on April 04, 2015, 08:14:34 pmCould you point to his opinion? Please, I'm a newbie!

author: tautech
author_rank: Super Contributor
timestamp: April 05, 2015, 03:02:08 am
content: Quote from: Circuiteromalaguito on April 05, 2015, 02:37:12 amWell to summarise, the mostly now 20+ year old CRO's are reaching the end of reliability. This statement I know WILL incite all sorts of responses, but bear with me.For a NEWBIE, the possibility of maintaining and repairing a CRO, while fascinating, will be a substantial diversion to the projects they are working on. Been there done that myself.Many may have the skills and equipment to do so, and good on them.But if you are starting out and budget is not a great concern, DSO is the way to go.The features they now offer are amazing.Yes the Wuerstchenhund is correct, Dave has lately made several posts in various threads very similar to this one, recommending a recently introduced DSO. Can't bring myself to state the brand.

author: timofonic
author_rank: Frequent Contributor
timestamp: April 06, 2015, 09:32:12 pm
content: Quote from: tautech on April 05, 2015, 03:02:08 amWhat if there's limited budget? Is better an old analog or a cheap digital?

author: tautech
author_rank: Super Contributor
timestamp: April 06, 2015, 10:03:51 pm
content: Quote from: Circuiteromalaguito on April 06, 2015, 09:32:12 pmIMO, regardless of budget is ones ability to keep an old CRO working.Circuitry in CRO's, especially the HV supply for the CRT is often problematic, irrespective of component quality used, it is the nature of the beast.Even the signal path, sweep and low voltage circuitry needs another scope to diagnose faults.Consider that if you invest in an CRO, it is not without risk.If one has the skills and tools but not the budget, it is indeed an option.Always ensure a Service manual is available too.Even the very low cost DSO's offer SO many more usefull features that a CRO doesn't.Reliability is almost unquestionable.But consider this very old wise saying: First cost= last cost.If you don't want any hassles get a DSO.

author: Fungus
author_rank: Super Contributor
timestamp: April 07, 2015, 02:11:13 am
content: Quote from: Circuiteromalaguito on April 06, 2015, 09:32:12 pmThe answer is still: DS1054ZThe price difference between 'old analog' and 'cheap digital' is a lot smaller than when the "get an old analog" advice was handed out.At best get a *really* cheap old analog just to keep you going while you save up for a digital. There's no way you should be paying more than $90 though unless it's a really high bandwidth 'scope that you can re-sell when save up enough to get your DSO.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: April 07, 2015, 05:24:21 am
content: Quote from: Circuiteromalaguito on April 06, 2015, 09:32:12 pmIf the budget is $100 or less then there's probably very little choice and an old analog scope looks like the only option. But it still leaves you with all the drawbacks, and very likely due to it's very limited capability will quickly become a dead end which requires further investment to replace it anyways.If budget is an issue then I'd say rather wait and save a bit more and buy a decent entry level DSO. Like many other hobbies, to start with Electronics properly requires a certain minimum investment where if you try to cut corners you'll very likely end up flushing money down the drain (try to get into say building and flying model aircraft with only $100 and see how far you get).I'd say unless the analog scope is free and working save the money and get a DSO.

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 07, 2015, 07:22:25 am
content: If $100 is budget, you can snag a nice analog one for $50 and save the rest. As for longevity, I've never owned a scope that wasn't at least 20 years old and bar minor issues they've been very reliable. Optimum age for repairability is late 1960s to mid 1980s. No valves and no custom ICs.The most basic thing, even 20MHz bandwidth is probably good enough for a first scope. After that, get something nice.At $50 if it does die miserably after 6 months, you can still harvest it for bits.I wouldn't buy a DSO for personal use (I would if I was doing this professionally).