Re: tek 7xx4 series brightness dimming after power on

Tom Bowers


I have a 7904A and it works exactly as you describe. I consider that
normal, nothing to worry about. Just a minor annoyance.

Tom Bowers

On Mon, Jan 6, 2020 at 8:29 AM Alberto, IZ2EWV <iz2ewv@...> wrote:

Hello dear friends,
I own three beautiful oscilloscopes from the series 7000: a 7904A, a 7104
and - the most recent arrival - a 7854.
Some of them had common issues, after powering on (failure at the RC
snubber and the AC line filter - which I replaced with new components and
everything come back to normality.
I ask you about a behavior that is common to the 7904A and the 7854: at
power on, the traces and the readouts are bright, but after some minutes
they dim: to restore the brightness it’s a matter of little correction on
the related controls.
By the way, I ask you if it is a normal situation (e.g. “normal” at the
time that the equipment was younger, by memory of somebody of yours) or if
it is a sign of aging of some component in the main power supply or in the
HV power supply. In this latter option, I ask you advice to let me get
closer to the problem (I have the service manuals).

Tnx es 73 de Alberto, IZ2EWV

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