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Tektronix 2430 DSO question — Parallax Forums

Tektronix 2430 DSO question

Martin HodgeMartin Hodge Posts: 1,246
edited 2013-08-13 05:41 in General Discussion
Anyone with Tektronix experience?

I just bought a used Tek 2430 150MHz Digital Oscilloscope off eBay and so far I really like it. This being my first DSO I'm ignorant on what to expect from it. The only thing that concerns me is what appears to be a constant noise on the trace on all V/div settings. I've attached two images, one at 5V and one at 2mv, with no probe attached. You can see the noise only changes a little from one extreme to the other. Is this normal? Is it normal for most DSOs or just this model? Or should I be seeing a more flat line?
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Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-06-26 14:33
    An input that's floating will always pick up a little noise, especially at those low voltage scales. Try grounding the input to see if that helps with the noise. Also, because the input is is converted to digital, you will always see one bit's worth of "bobble" if the voltage level happens to lie near the boundary between two conversion values.

    -Phil
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-06-26 15:33
    The noise is there with a grounded input as well. (grounding the BNC connector center-pin with no probe attached) I found a service manual PDF and tracked down the A/D section. Both channels are multiplexed, attenuated, amplified, massaged and stuffed through one thin coax into into a single 8-bit ADC (TDS5427) with a -0.5v to 0v range. So I guess there's quite a bit of "bit bobble" to be expected with an 8-bit system. The "averaging" function takes care of that very nicely anyway.

    Tearing apart this unit has been a lot of fun and very educational. I found and replaced a dead 1F cap that, along with a lithium battery, keeps the SRAM alive. Cleaned dirty contacts in one of the attenuator modules. And followed the external calibration procedure. But I did not know if this "noise" was normal for this unit or a sign of a problem (dry capacitors, etc.)

    Thanks for your input! I'm going to tinker with it some more.

    Post Edited (Martin Hodge) : 6/26/2010 3:39:16 PM GMT
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  • davejamesdavejames Posts: 4,047
    edited 2010-06-26 17:07
    ...wow! Tek sure packed that box!

    DJ

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  • skylightskylight Posts: 1,915
    edited 2010-06-26 17:59
    Can you get the "fishes" on the screen? that's a real test of a tek scope
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-06-26 19:27
    davejames said...
    ...wow! Tek sure packed that box!

    DJ

    Right on that one. Miles of 74LSxxx gates running at 20MHz and a 5" fan running flat out to keep everything cool. My 2215 by comparison is 1/2 empty inside, and light as a feather. There's a lot of hybrid technology in this thing that, while probably obsolete, is quite fascinating.
  • davejamesdavejames Posts: 4,047
    edited 2010-06-26 20:04
    ...nice thing about "obsolete" is that it doesn't mean "bad"!

    All my hi-fi equipment, all save one piece of my test equipment, a fair smattering of my collection of guitar effects pedals, all my guiatr amps, and cripes...even my computer since it's almost 6 years old...would be considered (actually are) "obsolete".

    I like to think of them as.........."vintage".


    Smiles,

    DJ

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  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-06-26 21:08
    Re-reading my post, it might have read like I was putting it down. On the contrary, I love it. While it's large, loud, heavy and power hungry, it's also RUGGED! Very few static sensitive parts, low noise susceptibility, it boots in under 30 seconds and the OS never crashes!
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2010-06-26 23:32
    I think I had the exact unit I got from a dumpster at the TRW swapmeet like 6Y ago ..


    It was In Bad shape inside so I scrapped it ..........I kept many of the parts from inside ..Knobs and most of all I saved the attenuators as there Precision for RF lab work . I Still have yet to use them ..

    peter KG6LSE

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    "Carpe Ducktum" "seize the tape!!"
    peterthethinker.com/tesla/Venom/Venom.html
    Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway. —Tanenbaum, Andrew S.
    LOL
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-06-27 01:41
    I'm seeing some screen shots of other Tek digital scopes of this era and they all show the same minor anomalies on a quiescent input. So it looks like my inexperience (and marginal OCD) is to blame on this one.
  • ppaing126ppaing126 Posts: 1
    edited 2013-08-13 05:41
    Hello Martin,

    I have purchased a 2430A from an auction. How do you did to clean the noisy attenuator..? mine has this problem in the B channel.
    I just replaced the battery but my ennglish is not good so I do not get exactly the manual steps to dissassemble and unmount the attenuator.
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