Re: One more quick question about CRTs

David Kuhn

With an instrument, in my industry, that we use to work on, the KB6000, we
significantly INCREASED the life of the CRT by lowering the
filament voltage. We went from a filament transformer rated at 6.3 volts to
one rated at 5.2volt (I think, or maybe 5.0) and the tubes never failed on
on us again. If I fire one up today, it looks as good as it did 25 years
ago. Before with the higher filament voltage, we were lucky to get two
years from the tube, in 24hrs/day/365. It was rated for 6.3 volt
filament. Its possible if the original transformer was for 110vac that
running on 120vac cause a problem. All I know is that the new transformer
allowed the CRTs to last, virtually indefinitely, and the presentation was
better. They used Telefunkin tubes, if memory serves correctly.

On Fri, Mar 27, 2020 at 10:20 AM Ernesto <> wrote:

Since I realize the vast expertise in the group, I want to ask a question
for which I didn't find an answer.
It is about the life of the metal oxide cathode in a CRT.
In vacuum tubes, insufficient electron emission due to insufficient heat
can shorten the life of the cathode, the tube.
This is why my 547 scope has a time delay before the higher voltages turn
Is the CRT included in this precaution, or is it only for the regular


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