Re: Advice about buying a 7904

Dave Daniel

The 7904A is easier to wotk pne because it has the “kickstand” feature where one can split the display section up off of the lower section to make repairs. I’ve never compared the specs of a 7904 and 7904A. I imagine they are quite similar. I’d probably buy a 7904A if I had to choose. As far as I know there are well-known problems with either ‘scope.

If it were me, I’d also consider a 7854.

Selecting plug-ins is a pretty deep subject. 7A26s with 7B92s is a good choice for general purpose work. IIRC, 7A19s are 50 ohm input only.

Once you get a 7xxx ‘scope you will probably want to get a differential amp, pulse and counter plug-ins as well. It’s a rabbit hole.


On May 28, 2020, at 18:50, Reginald Beardsley via <> wrote:

I have a 485 and a 7104. The onlyfragile CRT of the latter discourages regular use unless needed. Reed refurbished my 485 and obviously it's a really fine instrument.

I'm mulling over getting a 7904 for more routine work because I find the overshoot on DSOs very annoying. My 1.5 GHz LeCroy has a spec of 17% overshoot. I don't consider anything above 2-3% acceptable. I've asked Tek for a step response for a 3 or 4 series 1 GHz DSO using one of Leo's pulsers or similar. After my adventures with Keysight's MSOX3104T and the Rohde & Schwarz RTM3104 I don't want to get a demo unit unless it has an acceptable step response. It will be interesting to see if I get one.

I've never touched a 7904 and have no knowledge of them other than what I've read on TekWiki.

So some questions:

which is the best choice from a long term support basis, 7904 or 7904A?

what plugins? 2x 7A19 and 7B92 + ???

common issues (e.g things like the 576 transformer problem)?

anything else?


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