Re: Oscilloscopes to look for

> I wouldn't go for a 4xx series now. There are a number of plastic parts
> in them, and they are all now quite brittle. I picked up a 2465 on eBay
> a couple years ago, and it is quite nice. Probably more scope than you
> need for general testing, though. There are a number of good scopes in
> that series, the 24xx is a higher grade of construction, etc. than the 22xx.
>
> There are a number of outfits that make digital storage scopes and
> digital scope pods for attachment to a PC. The pods are certainly
> small, and if you have a PC handy, that may be a good way to go. Tek
> DSOs are likely to be pretty expensive, even used. The ones we use at
> work are about $10K (new price).
>
> Jon
> >
> I wouldn't go for a 4xx series now. There are a number of plastic parts
> in them, and they are all now quite brittle. I picked up a 2465 on eBay
> a couple years ago, and it is quite nice. Probably more scope than you
> need for general testing, though. There are a number of good scopes in
> that series, the 24xx is a higher grade of construction, etc. than the 22xx.
>
> There are a number of outfits that make digital storage scopes and
> digital scope pods for attachment to a PC. The pods are certainly
> small, and if you have a PC handy, that may be a good way to go. Tek
> DSOs are likely to be pretty expensive, even used. The ones we use at
> work are about $10K (new price).
>
> Jon
>

I used to work for Tektronix, first repairing the scopes and then selling them in the late 60's and first half of the 70's. I still have an engineering model 475 that more or less works.

When one selects an oscilloscope, the first question is what is the bandwidth required. That can be a difficult question to answer. If you buy too much, you are probably safe but it is more expensive. If you buy to little, the scope might not even see the signal.

If one is contemplating a digital scope, the sampling rate has to be 10X the frequency of the signal or the shape will not be captured adequately.

If the events to be observed are of low repetion, then if a digital unit is unaffordable, a suitable camera may be the only way to really 'see' the signal. Suitable in this sense means something that will hold the shutter (mechanical or digital) open until the even passes. Normally has to be fairly sensitive too.

The timebase needs evaluation too. Is the signal repetitive at a rate that allows me to easily see it or is it an infrequent event? Is the signal the triggering event for the scope sweep or is there some triggering event that is displaced in time enough that one trigger from it and see the signal in any detail. If the delay is sufficient, you may require a delayed sweep feature.

Then there is the issue of hooking up to the signal without distorting it. Oscilloscope probes are fairly good but probably more measurement mistakes are made by inappropriate use of scope probes than any other means.

In troubleshooting digital signals, I find a good logic probe to be of more general use than the scope.

A bit of warning about purchasing older oscilloscopes. Tektronix does not make the jugs (display tube) anymore. So if you find one you think you'd like to take home, excercise everything. Don't accept a burned screen and check the jug for double-peaking. To do this you turn the brightness down and then increase it. As brightness goes from minimum to maximum, it should do so in a continuous manner. If it increases, then decreases and then increases again, the tube cathode is reaching its end-of-life and it is not emitting enough electrons. What that means is you may, if you use the scope all the time or just leave it on all the time, have a useless pile of electronics on your hands.