Oscilloscope for home duty

[SSDIY]

Hi, I am new in using oscilloscope, I just got a Tektronix 20MHz scope. I was told 20MHz is good enough to use for most audio applications. Is that true or it is better to get a 50MHz or even 100MHz scope? I am still playing around with it to perform some square and sine waveforms for the amplifiers I had built.

[Iain McNeill]

Well, it's a tektronix so it will have clean amplifiers and steady trigger and a GENUINE 20MHz bandwidth which is 90% of what you need. 20MHz will only be a limit if you are working on high frequency class D amps, SMPS's or debugging stability issues on amplifiers - even then it will still be useful. For GP audio work it will get all your audio projects working well enough.

Enjoy your new tool!

[funkytek]

Originally Posted by m8o

To all those in the know...

Thanx everyone for the input so far. I settled on a decent looking (I have to see once it's delivered) Tek 465B with DM44 multimeter that I won for a good price on eBay. But no probes. As the seller wants something like 60$ for the 465B manual that he's selling in another auction (but not convering the DM44 ; forget about it either way), I found some scanned 465B manuals, so I know the probe is P6105. The only scanned manuals I found including the DM44 were for the 475.

Now for the questions:

1) Can I assume the 475+DM44 will work fine for my 465B+DM44 in regards to just the DM44 part? I ask, because I understand after 465B/466 the scope's circuits changed a good deal. So my worry is that affects the DB44 part somehow.

2) Can I depend on the probes stated in that 475+DM44 document for the DM44 section's current probe and temperature would work for my 465B+DM44, as far as the DM44 is concerned ?

3) What other probes would work for me -- say high voltage probes if I do work with Tubes in the future -- for the 465B, or what probes will work that may have come with later models?

Is there a cross-reference anywhere? It's not on Tektronix's site as far as I could find; at least not one that covers the 465B in it if it exists?

4) And finally, can I 'trust' non-original-Tektronics , aftermarket, probes I find being sold new on eBay? Like this:
http://cgi.ebay.com/For-HP-Tektronix...QQcmdZViewItem

Thanx very much again!

Mr. Gootee gave some good answers, but yes on the probes. All the probes for the 475 will work fine on the 465, including the DMM probes. Just not the newer style probes that get power and indicator signaling from the scope (via a ring around the BNC connector)

I have a set of those ebay cheapo probes you mention in #4. They look pretty cheap. I haven't actually tried one yet. I just got them because I was curious. I will plug one into my 465 and see if I can get it to compensate etc. But maybe not until this weekend.

[funkytek]

Originally Posted by CBRworm

My goal - to spend less than $1,000 on ebay for a scope. My needs are a scope that is probably less than 100mhz it might be nice to have higher, but I don't need it. Most of what I look at are power supplies and low speed serial data.

I am having a hard time figuring out where the different obsolete TDS scopes fit in the hierarchy. I don't need high Mhz, and the LCD display of the TDS200/ 1000/2000 series is appealing to me (because of size), but I don't know how they compare to the older higher number TDS series scopes like the 300,400,500,600 etc.

I have not used a digital scope in the past, always analog. I understand that these newer digital scopes have the ability to display realtime waveforms much like an analog scope (if this is incorrect please let me know).

I see that the newer low mhz scopes have higher sampling rates than the older high mhz scopes. Is this relevant? I also have noticed that the LCD scope only has a display resolution of 320x240 where the CRT scopes were 640x480. Is this something that would noticeable? Seems like it would be. Again I am used to perfectly smooth analog scopes. I don't know if one of these newer ones would look grainy, or if it matters.

I am leary of buying a 22xx or 24xx vintage machine due to just generally being afraid of buying 15-20 year old sensitive electronics that I can't repair.

So it would seem my options are the TDS 200 series or the TDS 300-600 series.

any suggestions?

I have a TDS2014 (color 4ch 100MHz) and find it quite useful. I love the small form factor. I mean, coming from more traditional scopes, it is wonderfully small and light and (most important) of shallow depth. Because of this it fits into almost any test bench situation.

The other pros on these little digital gems are the super easy set and usage. I can take it out of the drawer and acquire a trace in a minute (mainly slowed down because the scope has to boot up). There are gobs of math functions you can do on the traces, including FFTs to look at the spectrum distribution (poor man's spectrum analyzer).
Having a color one is sweet because the traces are color coded with the color rings on the probe. Sweet.

The cons are that these, and most digital scopes, are only 8bits of resolution, though they sample at 1-2Gs/sec. So you can't simultaneously look at as much amplitude resolution as a good analog scope. But, ya know, I must have a dozen Tek scopes including 7854's, 2445, 7834, 7904 and even a 547 (best analog scope ever made, as long as convenience isn't a parameter) and the one I grab the most is the TDS. Then probably the 465 or the 2246A, then a 7854...depends on what I am looking for.

The high sample rate is useful for time-domain events allowing for better triggering. The faster the better, although it means a larger data set and smaller capture window, always the tradeoffs.

As to screen resolution. Well....there are times in audio design when being able to recognize the type of fuzz on a trace is valuable and then you want the best trace you can get. So I pull out the 547 watch the lights dim while it powers up it's 50 tubes. Or I grab the 465, if a smaller screen is ok, or the 2445. Yup an top rate analog scope rules the trace war, hands down. Unless you want to sell your house and get one of the big screen power scopes.
But, hey, it's digital. Say you are looking at some crap on a AC power line. Just demodulate it by subtracting a pure sine wave and presto, crap all by itself.

I wouldn't be afraid of a 2200 series Tek scope though. If it works well when you get it, it will stay that way unless you kill it.

Sorry, rambling. From what you state as your needs, I would think a TDS2000 series would be perfect.

[funkytek]

Originally Posted by gootee

Yes, a 2465 (or A or B) is probably the best portable analog oscillocope ever made.

Shhh! Say that quietly. I was hoping the prices will drop.

Originally Posted by gootee

And yes, you cannot get actual "new" replacement parts, directly from Tektronix, anymore, for (at least) the 2400-series' Tek-custom ICs, some of which were prone to early failure. [Tek sold basically their whole IC operation and basically all of their IC designs to <some well-known IC manufacturer> (was it Maxim, maybe?), who then promptly refused to make them anymore, at the low volumes Tek wanted, killing the 2400-series!]

Yes, it was Maxim. Tek should have realized the tiny volume on those lines were not enough to keep them going, but that was a problem with the whole captive fab thing.

Originally Posted by gootee

And, FWIW, back when I was buying large lots of used or surplus scopes, the 2465 family was the ONLY type that never included ANY dead ones, and, in fact, presented no functional problems at all, when received in lots that could not be tested before bidding.

Shhh again, dang you are killing me!

Originally Posted by gootee

Additionally, last I heard (a year or more ago), there were some guys on the TekScopes group who had some friends who were considering fabricating reverse-engineered replacements for some of the most-sought "unobtanium" Tek-custom ICs. But I haven't been following that group's message traffic, since then.

Yeah, right, then they woke up in a cold sweat. They aren't technically ICs. Yes the modules contained custom bipolar (Super High-3 was the process) ICs inside, mounted on a Tek custom ceramic hybrid substrate with thick film laser trimmed resistors, inductors and caps. The ICs also had laser trimmed NiCr resistors. Cool stuff, state of the art back then. I still have one with a clear lid on it instead of the cast aluminum cover (that doubled as a heat sink). Yeah, I doubt anyone would fork over the cash to design, fab, package and test those again. What, for replacement part volumes? Heck they cost Tek more to make (back then) than the entire 2465 scope sells for now. I'll have to search out that thread, to see if I can get some of whatever they are smoking these days