Re: Tek 7834 Question


Brian
 

Hi GerhardMine does the same , or it did before the power supply went into tick mode , not had time to fix that yet . I put it down to expectations of a bi-stable screen like that in a 564 or a 549 but I think it performs differently because of the multi-mode features as every one I have seen a photo of in bi-stable mode shows the same bright background giving you only something like a 3 or 4 to 1 contrast ratio .
Brian

On Wednesday, 22 April 2020, 16:31:30 BST, Gerhard Hofbauer <gerhard.hofbauer@...> wrote:

Has anyone experience with the TEK 7834 400 MHz mainframe?

About 20 years ago I bought a used 7834 mainframe for the 7S11/7T11
plug-ins. At that time I wondered about the storage function.

When "Bistable" is pressed, the screen starts dark andĀ  gets completly
bright after abot 5 seconds. No adjustments of intensity etc. can adjust
the right brightness to get a good stored image.
"Var Persistence" is fine.

At the time I did not care, since I did not need any storage function.
Last year I decided to repair the scope, and I did all the tests and
adjustments of the service manual, but could not get even a bad
"bistable" screen. I read theĀ  "Storage Cathode-Ray Tubes and Circuits"
and "Oscilloscope Cathode-Ray Tubes" books and came to conclusion that
the CRT is probably defective. So I bought another 7834 with some other
defects (vertical), but it had the same screen effects.

So my question is: Is this a common failure of CRT aging, or am I doings
something wrong. (All voltages on the CRT are perfectly fine in each
operation mode)

br,

Grhard.

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