WTB: My first oscilloscope

[PedroDaGr8]

Looks like you have gotten some good advice. If you change your mind about the DS1074Z do know that TEquipment gives a 6% discount to EEVBlog members (mention it to them to get a coupon code). Also, the DS1074Z is more expensive but it is also a MUCH more capable unit overall. Now of course many of the tradeoffs between digital and analog apply but many are dramatically lessened with the Intensity Gradient aka Digital Phosphor display. Also, the Rigol is hackable in that you can get the basic DS1074Z an hack it to add (100Mhz, advanced triggering, 24MPt memory, Data recording, data decoding (I2C, SPI, etc.), an unofficial 500uV sensitivity mode that is a bit buggy). The triggering is one area where modern digital scopes shine compared to the older analog scopes. On an older analog scope you could trigger on height, slope, TV and occasionally a few other variations on those. Modern scopes have loads of triggering to more easily capture transients which are causing bugs. On the rigol you can trigger on : edge, slope, pulse, pattern, CAN, USB, FlexRay, RS232/UART, I2C, SPI, Runt, Windows, Nth Edge, Delay, Time Out and I think a few more. Some of these triggers come from the Advanced Triggering package which you can hack on. This ability to trigger on digital interfaces can be useful when trying to find particular bugs. Similarly, the 24MPt of memory allow you to trigger and just record until you find the glitch occurring.

This is not to say that this is the way you must go or should go. You know your budget and needs better than me. This is just something I thought should be mentioned. As I said, you have received some good advice so far, I just wanted to add a bit more to the conversation.

[GeorgeOfTheJungle]

Like I said, I am pretty new to this world, so I might have it wrong. The Saleae website describes the new (shipping soon) Logic units as having analog inputs, but as you might expect, the sample rates and max bandwidths are pretty low compared to a proper scope. For example the max analog sample rate on the model I ordered is 10 MS/s (bandwidth 1MHz). For the applications I've been messing with so far (I2C, SPI, MIDI and basic serial protocols) I feel like that is good enough. The digital sample rates / bandwidths are much higher (100MS/s and 25MHz).

I think that with a good scope on the bench you're going to find little use for the saleae. In 30 years I've never come across a problem that required a logic analyzer. Perhaps that's because I've never had one. Not even now that they're cheap.

Yes 8+ signals on screen at once looks cool, but its very rarely something you *need* to see, if ever. I got the DS1074z in April to have at least one scope with 4 channels, but channels 3 and 4 are still virgin, huh.

The only negative thing I can say about a 2232/2221A is that once you try a small one like that rigol you begin to notice how big a chunk of bench the 2232 requires. But you're about to discover that that tiny saelae takes up a lot of space as well because without a laptop it's useless.

On the other hand the databooks now are .pdfs, and the .pdfs are a google search away, and we can't live without checking the email at every minute, and may want to do a quick check in LTSpice, or google something else, so a laptop on the bench is something you're going to want to have anyway.

[GeorgeOfTheJungle]

Beyond just simply being more complex, the 2232 switching power supply has some odd failure modes besides just the aluminum electrolytic capacitors wearing out with age.  But I agree that the analog part is pretty straightforward and since the oscilloscope shares so much with some other oscilloscopes in the 22xx series, parts are easy to come by . . . except for the bezel switch assembly. :/

The SCR/preregulator/FET current limit board you mean, right? If so, yes, I still have a 2215 with the disease. It works if I bypass that and feed it directly from an external DC power supply. I haven't figured out yet the fix, but there are not any custom parts in there I think, everything are discrete easy to find parts, so I'm not too worried about it.

The bezel switch assembly is that below the CRT, with the 5 save ref push buttons? Mine are fine, but I'll touch wood :-)

[GeorgeOfTheJungle]

Feel free to share links to good deals on DSOs you might find! I appreciate all the help

I've found that the "make offer" button in ebay is much much more useful than what I thought :-)

[David Hess]

Beyond just simply being more complex, the 2232 switching power supply has some odd failure modes besides just the aluminum electrolytic capacitors wearing out with age.  But I agree that the analog part is pretty straightforward and since the oscilloscope shares so much with some other oscilloscopes in the 22xx series, parts are easy to come by . . . except for the bezel switch assembly. :/

The SCR/preregulator/FET current limit board you mean, right? If so, yes, I still have a 2215 with the disease. It works if I bypass that and feed it directly from an external DC power supply. I haven't figured out yet the fix, but there are not any custom parts in there I think, everything are discrete easy to find parts, so I'm not too worried about it.

The 2213 and 2215 are distinct from others of the 22xx series and are the only ones that used the SCR preregulator and FET current limiter.  They have their own issues like generating too high a CRT filament voltage for which Tektronix issued a change notice but they seem to be pretty reliable.

The 2213A through 2232 series (and the later 24xx oscilloscopes) have a universal input switching FET preregulator driving a saturable core inverter.  Over at TekScopes@yahoogroups.com we have had a couple that defied diagnostics and repair despite the design being pretty straightforward but of course off-line regulators are inherently difficult to scrutinize because of safety issues.  The bad ones tend to run for a while and then self destruct again without damaging the oscilloscope.  I have not been able to get my hands on one to find out what is really going on.

The 2201 through 2225 series have a different power supply design yet which which uses a 60 Hz transformer for step down and isolation before a low voltage buck preregulator and non-saturable core inverter and they seem to be more reliable.  I would have expected them to have problems with their voltage driven inverter but apparently that has not been an issue.  Maybe there are just fewer of them.

The bezel switch assembly is that below the CRT, with the 5 save ref push buttons? Mine are fine, but I'll touch wood :-)

I have a 2232 which needs a replacement bezel switch assembly.  The silver traces on the flexible printed cable tend to fail after a while and the only oscilloscopes which used that part are the 2221A, 2224, and 2232.

Some are repairable with conductive ink but it is difficult.

[PedroDaGr8]

Feel free to share links to good deals on DSOs you might find! I appreciate all the help

I've found that the "make offer" button in ebay is much much more useful than what I thought :-)

 QFMFT! I have also found that even it doesn't say make offer, a messaged offer often works as well.

[GeorgeOfTheJungle]

The 2213 and 2215 are distinct from others of the 22xx series and are the only ones that used the SCR preregulator and FET current limiter.  They have their own issues like generating too high a CRT filament voltage for which Tektronix issued a change notice but they seem to be pretty reliable.

The 2213A through 2232 series (and the later 24xx oscilloscopes) have a universal input switching FET preregulator driving a saturable core inverter.  Over at TekScopes@yahoogroups.com we have had a couple that defied diagnostics and repair despite the design being pretty straightforward but of course off-line regulators are inherently difficult to scrutinize because of safety issues.  The bad ones tend to run for a while and then self destruct again without damaging the oscilloscope.  I have not been able to get my hands on one to find out what is really going on.

The 2201 through 2225 series have a different power supply design yet which which uses a 60 Hz transformer for step down and isolation before a low voltage buck preregulator and non-saturable core inverter and they seem to be more reliable.  I would have expected them to have problems with their voltage driven inverter but apparently that has not been an issue.  Maybe there are just fewer of them.

I have a 2232 which needs a replacement bezel switch assembly.  The silver traces on the flexible printed cable tend to fail after a while and the only oscilloscopes which used that part are the 2221A, 2224, and 2232.

Some are repairable with conductive ink but it is difficult.

David, interesting and very useful, thank you!