Re: 2465B - Weak Readout Intensity


 

I would consider increasing the heater voltage as a test, and only as a test.  It does risk destroying the tube completely but it usually does increase electron output and can brighten a CRT.  So if an increased heater voltage corrects the dim display you have diagnosed the problem and can go ahead with CRT replacement in confidence.  .  But, as you, these instruments are too proud to suffer long term indignity.

On Monday, February 3, 2020, 09:35:01 AM CST, flanneltuba@gmail.com <flanneltuba@gmail.com> wrote:

I have to admit it is tempting to try bumping up the heater voltage and seeing if the tube will eek out a bit more brightness. Some part of me though can't bring myself to making such mods to a Tek scope of this particular pedigree. This old gal is too proud to stoop to a facelift! :) Another aspect that holds me back from this is knowing that this would really amount to a temporary fix. If the cathode is already spitting out its last gasps of electrons, forcing it to work harder surely will only bring desired results for limited amount of time. I would always be worrying that it would fizzle out at any moment. It also seems to me this technique would cause a considerable amount of extra heat to be generated in the tube, which feels bad somehow. I suppose if there were no surplus/used CRTs available at all, this would be a much more enticing path.

I recall using one of the old fashioned color TV CRT "restorers" on a Sony Trinitron sidewalk salvage back in my college days in the early 80's. It did the trick quite neatly as I recall. Never tried the grid-cathode arc technique. Sounds fun, but pretty chancy. Then there's the CRT neck whack... I'm just imagining the Wile E. Coyote comic moment standing there with that resigned look on his face, the imploding CRT in his hands in a halo of flying glass. We used to whack old hard disks that had developed "sticktion" in a similar fashion to the horror of any onlookers. Worked about 50% of the time.

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