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    Newbie intro and oscilloscope question

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    rdonahue

    Posts : 1
    Join date : 2016-05-15
    Location : Lancaster, PA

    Newbie intro and oscilloscope question

    Post by rdonahue on Fri Jul 22, 2016 4:55 pm

    Hi all,

    I am new to the forum. I'm currently saving up for either the VTA-70 or -120 and am in the research phase. I don't have much of an electronics background so I have been starting off small and moving up. I've built a few guitar pedals from kits and have a Bottlehead headphone amp kit on order that I plan to build before I move up to the VTA kit. I'm sure I will have a number of questions when I finally place my order and begin the project but I have one right now about test equipment and oscilloscopes in particular.

    I would like to slowly start picking up test equipment since I'm very interested in tube audio and want to learn what exactly is going on inside those circuits. One of the obvious pieces of equipment is an oscilloscope. My question is, for someone just starting out and wanting to have equipment that will last a while, would you go with a new digital scope like the Rigol DS1054z or an older analog Tektronix scope? I have a lead on what looks to be a good condition 2246 that is fairly close but I am thinking that it might be better for me to go with the new unit first since, if anything goes wrong with the older one I don't have the skills yet to get in there and fix it myself. What do you folks think?


    arledgsc

    Posts : 330
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: Newbie intro and oscilloscope question

    Post by arledgsc on Fri Jul 22, 2016 8:09 pm

    I have a Rigol 2-ch scope at home and a 4-ch. version at work.  The model you selected would be great for a beginner scope.  Just keep in mind the supplied scope probes and/or input to the scope may have voltage limitations that prevent you from measuring ripple on the 500V supply of say the ST-120.  But no issue on smaller signal levels.  You may be able to purchase different probes with higher voltage ratings. 

    Also the lower price scopes don't have a tremendous amount of bandwidth (these days) which would make it difficult to accurately measure risetimes on digital clocks.  The 50Mhz bandwidth rating is the -3dB response so it is already rolling off at that point.  In general you need 5x the bandwidth for the speed of the signal measured.  But for audio and general digital stuff looks good!

    https://www.rigolna.com/products/digital-oscilloscopes/ds1000Z/ds1054z/

    Peter W.

    Posts : 73
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Newbie intro and oscilloscope question

    Post by Peter W. on Wed Aug 10, 2016 3:38 pm

    rdonahue wrote:Hi all,

    I am new to the forum. I'm currently saving up for either the VTA-70 or -120 and am in the research phase. I don't have much of an electronics background so I have been starting off small and moving up. I've built a few guitar pedals from kits and have a Bottlehead headphone amp kit on order that I plan to build before I move up to the VTA kit. I'm sure I will have a number of questions when I finally place my order and begin the project but I have one right now about test equipment and oscilloscopes in particular.

    I would like to slowly start picking up test equipment since I'm very interested in tube audio and want to learn what exactly is going on inside those circuits. One of the obvious pieces of equipment is an oscilloscope. My question is, for someone just starting out and wanting to have equipment that will last a while, would you go with a new digital scope like the Rigol DS1054z or an older analog Tektronix scope? I have a lead on what looks to be a good condition 2246 that is fairly close but I am thinking that it might be better for me to go with the new unit first since, if anything goes wrong with the older one I don't have the skills yet to get in there and fix it myself. What do you folks think?


    A couple of things:

    a) Tektronix scopes are generally of excellent build quality, last a very long time, and are very reliable. For an analog CRT-based scope, you cannot do better. Writing entirely for myself and based on my experience, for a newbie, I would only recommend Tek scopes if CRT-based.
    b) If you can afford it, look for a good, used or new, FLUKE solid-state LCD-based scope. New, they are out-of-sight expensive, but often can be found used at a reasonable cost and within the range for general audio use. They are also truly auto-ranging so that you will not need a multiplicity of probes. Fluke scopes are far less hungry for real-estate, and are portable as well.
    c) And, if you (eventually) wish to move on to FM tuner alignments and such, you will need a scope at a higher MHz level than for general audio use. So, consider that in your equation.
    d) And last, A good scope, well kept, will retain its value more-so than most other pieces of test equipment. Meaning that you should be able to find a home for it (sell it in the future) should you either get out of the hobby, or decide to upgrade.

    One observation: I have been in this hobby for over 40 years now. I can count on one (1) hand the times I have really *needed* a scope to diagnose or correct a problem. As they are expensive, awkward, and greedy for real-estate, you might invest in other things first. If you are serious enough for a scope, then you will want a first class workbench first, and the tools to go with it, also first. Start with an Isolation Transformer, preferably one wedded to a Variac (AKA: IsoVariac). ALL mains-based, and even some battery fed tube equipment has lethal voltages inside. Some over 500V. An isolation transformer gives you some protection. Then, tools: I keep some very nice tools, not one of which is from China. Yes, I paid a bit more, but some go back with me almost 50 years - my ChannelLock box-joint linesman's pliers for instance. I also keep an VOM, LCR, and ESR meter, also all US-made. Excellent lighting (three (3) articulated lamps, one with an optical grade magnifier) and such. Third hand, soldering station, solder dispenser, and so on and so forth. I keep a very good tube tester, as well... the very last thing I acquired for test instruments.

    Point being that an expensive, complicated, and needs training, care and feeding item may want to fall back on the list until you are more firmly grounded in the process. Maybe, not certainly. The balance to that thought is that if you get used to, familiar and adept with a scope, you will be well ahead of most newbies in short order - for those tasks that need a scope.

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