Oscilloscopes - Are they important and what Kind is adequate

[gearhead]

Am in the process of looking into Oscopes myself, and came across two excellent Tektronix writeups:

http://www.valuetronics.com/Details.asp ... ronix_465B

Haven't chewed thru them yet, but have more than you probably cared to know

[thousandshirts]

I just got a Tektronix 475A, 250MHz scope.

It was quite a coincidence--I decided that I finally had to break down and get a scope, so I had been looking through the local Craigslist for sale ads to see if I could snipe a scope from a student just finishing up a course, or something. I found a good set of scope and generator for around $350. I looked around and thought, "I've got this acoustic guitar here that I rarely play, so I'll put that up, and have it pay for the scope." Well, at least, most of it.

I listed my guitar on Craigslist for a relative steal of a deal ($200) and within an hour I had a caller. We talked for a bit, and we arranged to meet up the next day, and it was sounding like a done deal. I thought I'd explain to him why I was selling a guitar like this, so I told him "although I'd like to keep it, I need an oscilloscope."

"Really?"

"Yep, I need to get an oscilloscope."

"Well isn't that funny! I have a real nice one here that I never use. Want to trade straight across? It's a Tektronix 250MHz 475A."

Long story short, he worked for the local phone company for years, and got this stuff as they were upgrading their equipment. He's going back to check on a HP signal generator for me, as well, in the neighborhood of $100.

Anyhow, this scope is WAY more than I need. But it was in superb shape, and the price was right! 1x, 10x, and 100x probes, manuals, the works.
Using it now to fix up a nasty PA amp (300w per channel, PCB) problem.
Currently using the function generator from e-dsp to make sine/square waves:

http://www.e-dsp.com/software-functionsignal-generator/

Moving right along!

[skyboltone]

Way to go mister. I got the baby brother of that one....A 453....50 mhz.
Does everything I need it to do.

[v846]

Way to go mister. I got the baby brother of that one....A 453....50 mhz.
Does everything I need it to do.

Those 453's are great little scopes, cheap and easy to fix. IIRC they are the last of the 400 series that don’t use proprietary chips..

I picked up a working one for $40 and later on a non working “parts unit” for $20 which needed a good cleaning plus a couple of transistors in the vertical output amp, now my main machine Also like the bright , sharp display..

[butwhatif]

Doing audio electronic work w/o a 'scope, is really like working blind, sure you can do it but at what cost timewise, and never really knowing sometimes what signal you're dealing with. I bought a new 15MHZ Leader scope 25 years ago and it has worked flawlessly ever since. In fact, I never turn it off.
Do yourself a favor and buy a new one, complete w/warranty, and you will be one happy camper. Check these out---

http://www.mcminone.com/product.asp?pro ... CMProducts

http://www.testequipmentdepot.com/leader/ls8022.htm

btw, you don't need anything faster than a 20MHZ scope for audio work

[thousandshirts]

btw, you don't need anything faster than a 20MHZ scope for audio work

That's right! 20MHz is plenty.

Excellent advice to get an affordable new scope with warranty, as opposed to a used, unknown scope with 10 times the bandwidth you'll ever use. The 250MHz scope I got could be used to build microwave ovens or some such. 250MHz is totally out of hand.

[d2camero]

He he - this should get some hackles up...

I use a USB scope. A 4 channel jobby from pico scope made for audio analysis.

I can do real time freq analysis, save the pictures, tweak and do it all again.

I can put in 4 probes throughout the circuit to see how the signal changes as it progresses throughout.

I can also do one-shots and freeze them on screen.

For a hobbyist this is probably overkill, but if you do a lot of audio analysis work it is great stuff.

I also have a two channel Tek scope that I use for quick checks.

d2

[jhaas]

Inspired by this thread, I recently picked up a Tektronix 453 off eBay for a reasonable price, and I have one Tektronix passive 10X probe on the way.

I'm totally new at this, and have much learning to do, so here is my newbie question.

Do I need, or is there any benefit to, having more than one 10X probe?

[peesinstew]

from what I've seen, the 453 is a dual channel scope, so if you get two probes, you can trace two signals at once and have them both displayed on the screen. This can be useful to see what's going on before and after any part of the circuit. I don't actually own a scope, so there's probably alot more you can do with 2 probes, but I'm not sure how much else is applicable to amp work.

[Structo]

He he - this should get some hackles up...

I use a USB scope. A 4 channel jobby from pico scope made for audio analysis.

I can do real time freq analysis, save the pictures, tweak and do it all again.

I can put in 4 probes throughout the circuit to see how the signal changes as it progresses throughout.

I can also do one-shots and freeze them on screen.

For a hobbyist this is probably overkill, but if you do a lot of audio analysis work it is great stuff.

I also have a two channel Tek scope that I use for quick checks.

d2

Sounds good to me.
I knew they made signal generators but a USB scope sounds like just the ticket.
What brand did you get?
Quite a price range on them.
Cheapest I saw was $129 on up to hundreds.

[d2camero]

Yeah, they are pricey. I have a 3424, which is about $1200 (I think). But it is used for lots of other audio work, so for building one or two amps it is a bit rich. There are a lot of other USB scopes out there, this was the only one I found that had the resolution for audio work.

d2

[gearhead]

I'm looking at a Tektronix 465; anyone have experience with that one? Can't seem to find any 453s; must be in a drought/wrong timing.

It's been eons since I used one. One of the spec diff's between the two that has me concerned is that the 453 has 10V per division, vs 465 is 6V per division.

With a 10x probe, that 100 and 60? For those 453 users, do you get close to pegging out the range? If so, the 465 might not do it.

Thanks all,

Dave

[v846]

Dave,

I use a 100x probe for the plates using the 453 though I probably could get away with 10X I wouldn't try it with an SVT I like to play it safe so use the 100X..
465 would be nice if its got a guarantee as it has proprietary parts which could be a pain to source..

[skyboltone]

I'm looking at a Tektronix 465; anyone have experience with that one? Can't seem to find any 453s; must be in a drought/wrong timing.

It's been eons since I used one. One of the spec diff's between the two that has me concerned is that the 453 has 10V per division, vs 465 is 6V per division.

With a 10x probe, that 100 and 60? For those 453 users, do you get close to pegging out the range? If so, the 465 might not do it.

Thanks all,

Dave

No. Thats just the stripes on the screen. The grid marks. You just change the volts per division with a knob. The 10 volts per division is easier and more intuitive to read. Unless you work in base 6 for some reason.

[gearhead]

Oops, mistyped. It is 5 volts per division MAX. It goes from 5 mV to 5 Volts per division. Looking at pics of the screen, there are 4 divisions above, and 4 below. With a 10X probe that would be (I think) 400V peak-to-peak.

Good enough for most preamp sections, but not power amp? That's where I was coming from, but not having an Oscope, don't know what I don't know. LOL.