This Oscilloscope - worth getting?

Discussion in 'General Electronics Chat' started by NZMikeV, Aug 22, 2010.

  1. NZMikeV

    Thread Starter New Member

    Jun 18, 2010
    22
    0
    Hi People,
    This oscilloscope is being offered on an auction site in NZ. I am contemplating purchasing it so I can see what's going on in my PWM (and other) circuits. It's a bit old but would it be a good starter-scope ?
    Price is NZ$50. I've never hd a scope before and can't afford a new one just yet.

    Blurb (from site):
    SERVICESCOPE manufactured by Telequipment about 1968. In good working order, complete with original detailed manual and six spare valves still in original packages (untested).

    Measurements: approx 14.5cm wide, 17cm high and 23cm long. Screen diameter is approx 7cm.

    Photo (from site): See attachment
     
  2. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    From the looks of it: no.

    Starting from the top:

    • Single channel only. Dual channel is pretty much a requirement in modern circuits. For example, you may want to follow a clock signal for a microcontroller, whilst looking at the data stream out of another pin. You can't do this with a single channel oscilloscope. In fact, as I own a quad channel oscilloscope, I'd say the more channels the better - but if you're only starting out dual channels should be fine.
    • Can't see any trigger on it. If any, it will be zero crossing, or not stable enough for serious use.
    • Very limited bandwidth. I wouldn't imagine it going much faster than 5 or 10 MHz. I recommend at least 50 MHz, if not 100 MHz. (Any more than that is going to be overkill for a beginner.)
    • Attenuation controls(?) I don't see any. They should be in fixed, calibrated values, not as a dial (except for some scopes which have a 'fine' or 'CAL' dial; but this should only supplement the fixed values, not replace them.)
    • It's not a digital (or even analog) storage scope. This isn't critical, but you will wonder what you did without it. If you have a digital scope, you can compare waveforms, and save them to memory. Don't underestimate how useful this is. A DSO is very useful, because instead of counting divs, you can just ask the scope "what is the peak-to-peak voltage" or "what is the risetime" and it will tell you.
    I highly recommend you have a look around for used electronic test equipment stores. I found one 8 miles away from me and they sold me a very nice HP 54501A DSO 100 MHz 4 ch. for £160 including a 100 MHz 10X/1X probe. It's still working great, and was even calibrated in 2006. The store specialised in collecting old test equipment from education and business and reselling it.

    Also, I would avoid equipment with valves. It is very difficult to find replacements if you break them.
     
    NZMikeV likes this.
  3. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    Looks pretty old to me, what kind of vertical amp and horizontal sweep response does it have?

    If it's only good for audio it's going to be kind of worthless for digital stuff.

    I bought a used Tektronix 2465 for $167.50 from http://www.techrecovery.com but you've got to call and see if they still have one and and willl make the same deal. They want a ton more for the A and B models but this one's fine for me.

    Look it up for the specs, it's one fine scope with tons of features.
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I don't know how much NZ$50 is in American, but $100 got me a dual trace 60Mhz scope with all the bells and whistles from a local ham convention, including two X10 test probes.

    If you're paying shipping I'd save a bit more and buy a better solid state model, the shipping alone is going to eat the advantages of a low cost scope (in other words, cost).
     
  5. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
    90
    A 7cm screen will drive you crazy.
     
  6. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
    804
    Not as much as uncalibrated time and attenuation knobs. These boxes used to be called oscillographs, because you can´t really measure anything without a precise timebase.
     
  7. NZMikeV

    Thread Starter New Member

    Jun 18, 2010
    22
    0
    Hi All,
    Thanks heaps for all the advice.
    I will pass up on the 'scope and look at saving towards a 'real' one.
    ;)
     
  8. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    Real ones can be found on the cheap if you're patient, even eBay occasionally has a deal.

    I've found it pays to be patient when dealing with eBay. One week there may be 10 of something but 100 people wanting them so bidding wars occur, a few weeks later 20 show up and nobody wants one so you can get the same thing a lot cheaper.

    When I first stated buying stuff on eBay I got addicted and was very guilty of being part of bidding wars, took a long time to learn to be patient. I picked up quite a few old Timex Sinclair "computers" (if you can call them that) for around $10 each, often with the extra memory module. For a while they were demanding top prices, then it seems everyoen that wanted one had finally bought one and whatever showed up from then on didn't draw much interest. Same with the TI 99/4A. Now I've got a pile of both and I haven't a clue what I'm going to do with them. I am hoping in time they'll pick up some value but for now it appears they were a lot more common than I ever thought.

    If you don't have an old Timex Sinclair and can get one for $10 with all the accessories they can be handy to have around. They program in Basic with single keystrokes representing the common commands. Inside is a complete Z80A computer with all the common interface chips. Built in cassette tape I/O for storage and they used a common TV set for the display. Options were the extra memory module and I think there was even a floppy disc at one time.
     
  9. mbohuntr

    Active Member

    Apr 6, 2009
    413
    32
    Generally, you get what you pay for. I picked up a older energy systems 30 mhz dual trace model. Works pretty good, but no calibration, unstable, and the upper ranges (above 100khz) is unable to adjust the trace to stabilize. $30. I learned a lot, enjoyed it, but will now save up for a digital scope w/ storage. It will be able to (at least partially) function as a logic analyzer as well.
     
  10. gootee

    Senior Member

    Apr 24, 2007
    447
    50
    You should even be able to find a lot better scope for that same price. But it needs to have "calibrated" horizontal (time) and vertical (voltage) settings. i.e. The knobs should set the vertical and horizontal scales to actual numeric values. And there has to be a "triggering" control.

    What is the exchange rate for NZ dollars to US dollars?

    On the other hand, if it's US$20 or less and you can spare the money and there's no shipping cost involved, it might be worth having anyway. Even the six spare valves might be worth well more than that and could help finance a better scope.

    My old Heathkit from 1969 was like that, 5 MHz, no calibrated settings, no trigger. But it was made with several of a certain type of Mullard 12AU7 (?) tubes, prized by tube audio enthusiasts (a few years ago at least). I had similar used tubes that went for about what I paid for the scope kit when it was new ($20 or $25). (I still have the scope and it still works, after a few electrolytic capacitor replacements.) [I was even offered $250 for my old Ameco AC-1 15-Watt CW transmitter, for which I paid $14.95 for the kit, when new, around 1969. I still have it, but only for its sentimental value.]

    Anyway, do some research on ebay for the valve prices...
     
    Last edited: Aug 23, 2010
  11. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    1 New Zealand dollar = 0.7078 U.S. dollars
    1 U.S. dollar = 1.41282848 New Zealand dollars (sqrt(2) to 2 digits... yay)

    Source: Google, accurate as of this posting.
     
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