Re: Advice about buying a 7904


Harvey White
 

I can speak of this from the 7904 perspective, since I have two that work, and some backup parts sources,

I had 7904's available, and no 7904As.

the 7A19 are the "appropriate" plugin for a 500 mhz single channel plugin.  However, they're protected by fuses which may be (impossible) hard to find.  The 7A29 has a higher bandwidth and is apparently not protected by fuses (and by something that can be reset), so I prefer them.

My general setup is a 7A26, 7D12 (with sampling plugin), 7D15, and 7B92A.

I've swapped the vertical plugins as needed, 7A22, 7A13, 7A24, 7A29.

I've used the 7B10 and 7B15, but only rarely.

Don't have the 7B8x or 7b7X to speak of, at least, I may have some of them, but don't use them.

I've had (generally) few issues, a hybrid perhaps bad, a PS bad, but nothing that I thought was system wide.

Harvey

On 5/28/2020 6:50 PM, Reginald Beardsley via groups.io wrote:
I have a 485 and a 7104. The fragile 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?

Thanks,
Reg


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