So which Tek scope should I look for?

[tonyptony]

I have the opportunity to dig through some old Tek gear, among them (if they are working properly) are 475s, 485s, and 2465s. Discounting the fact that I really only will ever use two channels (don't weight the 2465 better just because it has 4), which of these is the best performing scope? Doesn't the 2465 have Time Delay and the others not?

[john curl]

The 485 is a great scope.

[gootee]

John is right. But they are ALL great scopes and were the industry-standard workhorses of their time.

The 2465 was probably the best portable analog oscilloscope ever made. Its 300 MHz bandwidth (or 350 MHz for the 2465A or 400 MHz for the 2465B) is very nice. But its on-screen automatic measurement cursor modes can become very difficult to live without! Its calibration is mostly automated, too, providing you have the proper precision DC and frequency sources.

The main problem with the 2400-series scopes is that they contain Tek-custom ICs that are no longer made, at least one of which tends to fail too often. (But, somewhere in the message archives of the TekScopes group, at yahoogroups.com, there is a message-thread that tells which serial-number ranges had the ICs that tend to fail.)

In any case, make sure that you get probes that are sufficient for the scope you get. You can find a list of the originally-recommended Tek probes for each scope at Test and Measurement Instrumentation : Tektronix . And if you plan to try to perform accurate high-frequency (RF) measurements, then you will need some of the probe accessories, especially the special ground connectors.

[Enzo]

Just a thought. If you are doing analog audio work rather than digital stuff, 300MHz bandwidth doesn;t really have any advantage over 100MHz. Or 60MHz. All of those are more than enough for analog audio.

I mention that because you mention "if they are working." Light each one up and get a display on the screen. If you have no probe with you, just touch a paperclip to the center of an input jack to inject a noise signal. Exercise the various controls. Personally I would much rather buy a more basic scope that worked reliably and smoothly, than a "better" scope with noisy gain switches and other controls or intermittent function aspects. In other words I'd be looking for a useful instrument rather than a rebuild project.

But your needs may be different.

[gootee]

High bandwidth isn't just for digital work!

But yeah, take one that works well instead of a "better" one that doesn't work.

And yeah, you might not need more than 200 MHz for audio work. (You might need to see RF in your audio system, not just audio frequencies.)

But you will find that most of the 2465's controls don't get noisy like those of older scopes do. And older or cheaper scopes will tend to become "rebuild projects" sooner than newer or high-end scopes. And calibrating a 2465 is an absolute breeze compared to calibrating a 475. And if the 2465 works, it will be a MUCH more useful instrument than any of the older scopes.

Trust me. I've had many dozens of Tek 475 scopes pass through here, and have bought, refurbished, and sold MANY different Tektronix (and other) oscilloscope models. I loved them all! But eventually a Tek 2465 is what I kept to use as my personal scope.

I also have a 500 MHz Tek 7904A and plug-ins (perhaps the best analog oscilloscope ever made), and some 475s, and a 453 and a 454, and probably a 2235 or two, and quite a few others. But the 2465 is what I keep on my bench.

[john curl]

Hi bandwidth is good for professional audio troubleshooters, because high frequency oscillations can not be seen by lower frequency scopes. Had them all over 5 decades.

[tonyptony]

A wealth of good advice from you all, thanks. Unfortunately I lost out on the 485. Somebody got to it ahead of me. Haven't had a chance to sort through any of the others.

[nickds1]

Vote here for a 2465 (a,b). Fantastic 'scope. I have a 2465A as my main 'scope - used to have a 7904A as well, but that developed "the click of death" (SMPS failure), so I gave it away. Still got a 2430A but hardly ever use that.

Analogue 'scopes offer so much more that pure digital ones - you get to see everything - nothing is missed.

I had a channel 1 attenuator failure and replaced that, but nothing else has ever gone wrong with it. Lovely 'scope.

Cheers

[star882]

Originally Posted by john curl

Hi bandwidth is good for professional audio troubleshooters, because high frequency oscillations can not be seen by lower frequency scopes. Had them all over 5 decades.

I remember reading that for through hole power transistors, ringing from poor layout or incorrect gate drive design is around 100MHz. It can be even higher for SMD. But you can also use a spectrum analyzer to check for that.

And of course, there's plenty of high frequencies in digital audio.

[tonyptony]

Originally Posted by gootee

The main problem with the 2400-series scopes is that they contain Tek-custom ICs that are no longer made, at least one of which tends to fail too often. (But, somewhere in the message archives of the TekScopes group, at yahoogroups.com, there is a message-thread that tells which serial-number ranges had the ICs that tend to fail.)

I know this is an incredibly old thread, but I'm finally getting my hands on (what I hope will be) a decent 2465A. I did get one a while ago during the time of this thread but it turned out to be a dud. I wanted to know if anyone could help me find the thread referenced here. I did a search on U800, serial number, and some other terms for the Yahoo group and couldn't find the serial number range postings.