Re: A possibly sick 7904A


On Wed, Aug 19, 2020 at 09:24 PM, Eric wrote:

I have shied away from the MCP CRT as read some where that those tubes were
all on borrowed time as even at very low levels on intensity there was some
slight phosphor damage.
I think that's generally true, though it shouldn't be exaggerated. Acceptable brightness levels are fine and the 'scope does have some protections.

OTOH, some people like to see how bright the image of their 'scope will go. That's not what these 'scopes were designed for:
A few years ago, I had a friend who proudly showed me the screen brightness of his newly acquired 7104, the only problem being that brightness couldn't be turned down. Obviously a DC restorer problem or the like. After repair there was very little permanent (local) loss of brightness and no burned spots were visible. Quite different from the HP 1727A analog storage 'scope that turned out to have burnt its target.

The CRT in the 2467 appears to be far more resilient than the much older design in the 7104. It has better protection as well I guess. At low/normal brightness levels, life should be fine.
I only use a 7104 when I especially feel like it. It's not the best choice as a regular 'scope. Its screen graticule size is a bit smaller than regular models' as well (8mm/div vs. 10mm/div).

AFAIK, the 2467BHD, with its MCP CRT, was intended for regular HDTV-work.

FWIW, the CRT of my 7104 is as new, as are the CRT's of my 2467B and 2467BHD.


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