Tell me about oscilloscopes

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by webs, Oct 2, 2008.

  1. webs

    webs Supporting Member

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    I'd like to get an oscilloscope for testing amps and radios.
    I've looked around online but I'm suffering from a little data overload.

    Are there a certain few brands I should be looking for?
    What's a good place to buy? Most of the places I see are either only set up for big orders or have limited selection.
    I don't need any digital capability. Storage would be a big plus.
    I'd rather not go the computer-based route if I can help it.

    I'm on a strict $250 budget for the scope, probes, and signal generator. That looked reasonable until I was told that ebay isn't a good option, and that new is the way to go.

    Any help here would be great.
    Colin
     
  2. Tonefish

    Tonefish Member

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    FWIW I think there are decent scopes and signal generators on eBay. I recently bought a Tektronix 2246a scope for $192.50 including shipping (before eBays 10% off coupon), and a BK Precision 3020 signal generator for $48 (free shipping coupon from eBay), so your budget is not out of line.

    I would suggest that if you go this route that you limit your bidding to equipment that has been tested. There's a lot of people who buy surplus stuff from governement auctions by the semi-trailer load. This has some great gear in great shape and some junk. The only way you know which you are getting is if it has been tested. If the auction states tested and in good working condition, you have an expectation of condition that PayPal will support if it turns out not to be so.

    Both brands listed above are highly reputable.
     
  3. gregc

    gregc Member

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    I like Tektronics & LeCroy. A digital, self-testing unit is probably a good bet though I have a fondness for older, analog scopes. I wouldn't recommend them for the casual user though.
     
  4. webs

    webs Supporting Member

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    Thanks guys,

    I'm having trouble finding self-testing units. Are most digital units self-testing or how would I find out if they are?
    Digital does look like the way to go- I'm definitely a "casual user."
    Tonefish, you're definitely right about surplus junk on ebay- almost all of them are "as-is" in this price range.
     
  5. SatelliteAmps

    SatelliteAmps Member

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    Can't go wrong with a good Tektronix. I prefer the analog ones, but the digital are nice too. The digital are much more expensive. I've got three Tektronix analog's and two digital's. The analog's get used all the time.

    I also have a small B&K for taking with me. It is a bare bones deal, but it is good to have for traveling with.
     
  6. donnyjaguar

    donnyjaguar Member

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    Amateur Radio Fleamarkets, or Hamfests as they are called are a great place to find this sort of thing. I still have my 40$ Dayton Ohio 'scope I bought in 1989. Its good to 25MHz, dual trace and has V and H inputs for Lissajou testing. It also has a trigger that works well on complex waveforms. I have two identical 100kHz sig-gens that I paid less than 100$ for both. Mind you, both were broken when I got them but repairs were very inexpensive and basically involved replacing resistors and capacitors that had gone out of tolerance.
     
  7. stratman_el84

    stratman_el84 Member

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    For 'scope brands, Tektronix is the way to go. Most anything in the 2000-series models are quite good for one of the more-modern models. I prefer my old Tektronix 453, a real classic and widely considered the "gold standard" of analog 'scopes by which all others are judged.

    I find that analog 'scopes seem to be more practical and useful for most amp & radio work. However, I'm an old fart so YMMV. You can still find used Tek 453's being sold calibrated and tested by test equipment dealers/calibration shops because it's still such a good tool and still in demand, even with all the whiz-bang digital stuff out there. Some googling should turn up a few dealers.

    Cheers!

    Strat
     
  8. webs

    webs Supporting Member

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    What makes an analog scope more desirable than a digital one?
     
  9. SatelliteAmps

    SatelliteAmps Member

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    Price, quality, tubes, and response.

    Some cheap digital scopes don't trace signals as well as older analog ones. Mid to high end digital scopes can do it quite well though. Some have choppy responses. Cheap is cheap though, because cheap analog units suck too.

    High end digital scopes can get into many thousands of dollars, and can trace way outside of the range that a tube audio circuit needs. A high end used scope can be had for a few hundred dollars.

    I prefer gear that is built very well. If you look inside an old Tektronix, you will see how well built they are. Insane hand wired and tested gear. (most Tektronix require silver solder to work on them, for quality reasons. Most also come with a roll inside the scope, in case you ever have to work on it.) There are no circuit boards, no crappy Chinese parts, and if it has lasted this long, with good care it can last for 40 more years, easy.
     
    Last edited: Oct 5, 2008
  10. stratman_el84

    stratman_el84 Member

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    +1 on everything Adam said. The older Tektronix equipment is just insanely well-built. My first Tektronix 'scope was an old 500-series 30 mHz 2-channel all-tube unit that used various plug-in modules. I got it with the matching cart, which was good because the thing was *huge* and weighed at least 150-200 pounds! It contained on the order of 50 tubes. What a great old 'scope though! It served me for many years. Wish I still had it.

    I used to joke that in a few hundred thousand years or so after man is long gone from Earth aliens will be visiting and be picking through the rubble of an ancient city, when they'll suddenly notice a strange green glow coming from under some rubble. They'll dig down to investigate, only to find some technician had forgotten to turn off his Tektronix 453, and it's still sitting there happily tracing away.

    Other than the build quality, older analog 'scopes like the 453/454 are much quicker and easier to work with than many digital 'scopes, especially the lower-cost models, for common guitar amplifier/amateur radio workbench tasks. It's sort of like trying to gig with a digital effects processor with all the menus and patches to scroll through, etc when a couple good pedals and a tube amp would be much easier to use onstage and (IMO) sound better.

    Analog 'scopes seem to be a bit better at showing 'trends' in a changing waveform, similar to how an analog meter can be much better at showing a trend of change to a voltage when adjusting something, and to display rapidly varying signals in "real time" (or as they occur). This is especially useful when adjusting power tube bias, or looking for intermittent noise, oscillations, or other similar problems in an amp.

    Their trigger circuits (what locks onto a waveform and "freezes" it in place for display) seem to work much better for 'dirty' audio and RF waveforms, and to much lower signal levels than many digital 'scopes, at least until you get into digital instruments costing thousands of dollars.

    Here are a couple excellent web resources on 'scopes in general, and on older Tektronix 'scopes.

    General 'scope use basics: https://www.cs.tcd.ie/courses/baict/bac/jf/labs/scope/oscilloscope.html

    Bills' Tektronix 453/454 Info Page: http://www.reprise.com/host/scopes/default.asp

    Bill and Stans' Tektronix Resource Site: http://www.reprise.com/host/tektronix/home/default.asp

    Cheers!

    Strat
     
  11. killer blues

    killer blues Member

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    I have an HP 1741A analog 100MHZ dual trace scope I got for peanuts, then sent it out for maintenance and calibration. Total cost was about 150 bucks. This is a top notch lab quality scope there are none better. I was also able to get all of the necessary HP probes for it cheap on ebay. This scope is considered overkill for audio, but alot of parasitic oscillation is in thr rf range which this scope is capable of. The dual trace is nice too. Don't forget an audio signal generator and dummy load setup. You'll have fun for hours!
     
  12. twinrider1

    twinrider1 Member

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  13. stratman_el84

    stratman_el84 Member

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    If it was re-tubed and checked, it could be marginally-useful. IIRC, I think that 'scope was a 3 or 5mHz or so bandwidth model, so it's usefulness for detecting and viewing small waveform changes like that in crossover-notches when checking power tube operation when adjusting bias would be "iffy".

    Much would depend on the operators' experience and skill in interpreting and understanding what they're seeing, while taking into consideration the 'scopes' limitations.

    Cheers!

    Strat
     
  14. SatelliteAmps

    SatelliteAmps Member

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    The Model 34 is a pretty low quality scope. Might be worth playing with as a first scope, but I think you will run into it's limitations very quickly, even if it was retubed, capped, and calibrated.
     
  15. mark norwine

    mark norwine Member

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    I agree on Tek....can't go wrong with their older (yet solid state) units. "State-of-the-art", c.1969!

    My personal favorite is the Tek 422. Dual trace, 20mHz, small footprint on my bench.

    EDIT: I have no affiliation, but here's a clean 453 on ebay

    http://cgi.ebay.com/Tektronix-453-O...256988684QQcmdZViewItem?hash=item190256988684

    And the seller's screen name is 1952_telecaster !!! How bad of a guy could he be? :)
     
  16. donnyjaguar

    donnyjaguar Member

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    Much as I love tubes, I wouldn't recommend any 'scope that uses them. They have trouble on complex waveforms and some take so long to warm up that they are left on 24/7. Many 'scopes are hybrid, meaning a kluge of transistors and tubes. I'd avoid these also.
     
  17. SatelliteAmps

    SatelliteAmps Member

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    Gotta love the 564. It's a hybrid, but it is awesome. Works excellent for pretty much everything a tube amp throws at me. (And yes, I do have a few solid state scopes too, this one is just my favorite.)

    [​IMG]


    And the point to point wiring

    [​IMG]
     
  18. webs

    webs Supporting Member

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    Wow! That's some wiring.
    Do all those CC resistors give it a warm, vintage glow?:Spank
     
  19. dick wiewy

    dick wiewy Member

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    Try getting something de-soldered from those porcelain tag strips! Whatta muthah.

    I bought a 458 with the cart for a killer price. I wish I had gotten the manual with it!:mad:
     
  20. SatelliteAmps

    SatelliteAmps Member

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    It's not that bad with the right de-soldering station.

    Are you sure yours is a model 458 not a 485? I can't find anything on a model 458 at all, but I know where the manual for a 485 can be downloaded.
     

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