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Old 5th July 2007, 03:36 AM   #1
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Default Buying an Oscilloscope

Buying an Oscilloscope
1. It's important to keep in mind that a scope is a highly complex piece of electronic test equipment, and not only has to be functional, but correctly calibrated to actually be useful. Many scopes can be broken down into these rough categories:

A. Known bad or broken (Consider it as parts only, or repairable if you are highly skilled with access to parts)
B. Unknown condition and calibration, not shown with a trace (LEAST Desirable as a usable scope)
C. Unknown condition and calibration, but shown with a working trace (Worth considering, especially if you have lab access)
D. Condition known good, shown working (Very desirable, even for those unable to fix it themselves)
E. Known good, provided with calibration and warranty, shown working (Best possible for all buyers)

2. People sell scopes for many reasons, not all of them good for you. The unit many have problems, especially subtle ones, that can't be fixed, or the unit may be in poor condition, damaged or very old. As general rule, buy NO SCOPE unless it is shown working, unless you only intend to buy it for parts. And certainly buy nothing with no picture at all, the classic tell-tale of a disaster in the making. On the positive side, many excellent instruments get sold off as sites downsize or get new equipment, and there are some excellent buys to be had.

...read the full guide with pics here
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Old 5th July 2007, 06:45 PM   #2
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Hi

In every case to purchase an used scope is as a lottery.
Some are almost new and they originate from stores or military equipment.
Others originate from factories that they have used them for testings
= many hours of operation
Others originate from private laboratories and they could have been modified.

My opinion is that it is not worthwhile to purchase used scopes on-line
if it is very expensive.
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Old 5th July 2007, 07:09 PM   #3
Nordic is offline Nordic  South Africa
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http://www.measuregroup.co.za/index_files/page0149.htm

I found a local company that sells, repairs, recalibrates, and stock secondhand units....

See anything there that might do as a starter scope?
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Old 5th July 2007, 08:33 PM   #4
anatech is offline anatech  Canada
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Just to add,
Absolutely everything I have purchased off Eeekbay has been broken or not functional in some way, even guarantied good units. Shipping back across the border from Canada is a no flier after paying duties and brokerage fees.

For something like a primary 'scope, I'll buy new only. It's okay to buy secondary 'scopes used. Assume there is something wrong. Even if the picture is very good. (oops, we must have shipped the wrong one).

Pay attention to the brands and model numbers! Old Tek scopes have no real support, and newer there is poor access to parts and information. Philips have terrible reliability problems (I have one from new, PM series). HP stuff is better for information and access to parts. Old ones require donor units. I find that the HP stuff has a much higher build quality over most other units.

Pay attention how hot a unit runs. Philips "combi" scopes run hot as do parts of the PM 30xx series. New Tek units (DPO4000) run stinking hot somewhere - I will not touch one for that reason alone. Watch the size. Some older 'scope systems are huge, possibly making your power meter spin. The newer DPO4000 series from Tek is larger than your average scope (ie: it may not fit where you want to put it).

-Chris
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Old 6th July 2007, 11:29 AM   #5
mobyd is offline mobyd  New Zealand
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Quote:
Originally posted by anatech
Absolutely everything I have purchased off Eeekbay has been broken or not functional in some way, even guarantied good units. Shipping back across the border from Canada is a no flier after paying duties and brokerage fees.-Chris
I seem to have had exactly the opposite experience -
The two Tek scopes I have bought online (A 2445A on EBay ex Singapore and a 2465A on a local auction site) have both turned out to be "How did I survive this long without these" purchases.
Top whack scopes at decent prices. I don't miss my old Trio/Kenwood (which I did buy new) one little bit.
Cheers
M
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Old 6th July 2007, 04:27 PM   #6
anatech is offline anatech  Canada
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Hi mobyd,
That dealer (something99) seems to be pretty good, but shipping is murder to Canada.

It seems that there are many less-than-honest people hanging out in North America. I've purchased a few things that were in need of a ton of work from me. Even a pair of Tek 2235's that are semi functional. I won't buy any 24xx series due to the higher cost and the module issue. If one could be sure a 24xx series would last, it would be an excellent buy.

I've even had a number of flood damaged instruments (water babies) that were unmistakable. So in North America, assume it's busted. If it works, then you are ahead of the game.

-Chris
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Old 21st March 2010, 05:57 AM   #7
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Perhaps you can find small companies importing oscilloscopes and other test instruments directly from manufacturers, working on reasonable mark-ups, offering new technology equipment which comes with a guarantee.

One such company can be found at : Oscilloscopes :: Test and Measurment Instruments C.C.

This way there is no risk involved in purchasing used test instruments.
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Old 30th March 2010, 04:27 AM   #8
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Default craigslist scopes

On craigslist, it is a cash face to face transaction, no reputation required. I saw a scope listed for $25, took a transistor radio and a plug for a signal source, proved that the screen and trigger circuits work. Cool. Calibration is off, but I have 11 cent zeners to give me some sort of reference on voltage, and the wall voltage leaking out of my finger gives me some sort of reference on time. It is not that far off, about 25 %. Worth every bit of $25 even if obsolete for any sort of digital work. I'm fixing a Hammond organ and a preamp this month, 20 mHZ is fine.
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Old 30th March 2010, 03:40 PM   #9
star882 is offline star882  United States
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Quote:
Originally Posted by anatech View Post
I find that the HP stuff has a much higher build quality over most other units.
That was true in the past, but now HP is pretty bad quality, as a friend of mine found out.
Another use for the Kill-a-Watt... - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com
Quote:
BTW, I would not recommend HP stuff anymore. The power supply appears to be lesser quality than some other ones I have worked with. It was not the first time I had issues with HP, either. In one of my engineering labs, the HP oscilloscopes would intermittently fail to display the cursors. Very annoying when I'm trying to find the actual voltages. The "fix" is to rapidly cycle through several menus, which somehow clears the bug. And when I'm looking for deals on oscilloscopes, I would mainly look for Tektronix.
I believe HP sold their oscilloscope division to Agilent so hardware should not be a problem. Firmware bugs are definitely annoying, though.
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Old 4th April 2010, 04:23 PM   #10
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Do like I do. Sacrifice one of this year's vacation getaways to the Caribbean and get yourself a new scope instead. Actually a few years ago I sacrificed two years worth of vacations and splurged on a Tektronix TDS2024B. No regrets whatsoever.
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