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tabbypurr@gmail.com: Jan 04 09:23PM -0800 On Thursday, 4 January 2018 18:55:05 UTC, Terry Schwartz wrote:   > Any tube tester could be used to "rejuv" a tube or CRT. The process was well known in the shops. The key was always to leave the tube in the tester for some period of time after applying the 2X or 3X heater voltage for a minute or so (hopefully you didn't burn out the heater) and then seeing if the emissions dropped off unacceptably over the next hour. If emissions stayed up, the rejuv "took" and you were good. If not, maybe you sold a new tube.   > The problem with CRT rejuvenation was that the excess electron flow eroded the tiny aperture hole in the gun, causing blurry focus, smear, etc, on the face of the CRT. In lots of cases the customer didn't care, he did not want to spring for a new picture tube or new TV.   > I often got the job of replacing CRTs after the sets came back in when the rejuvenation didn't hold up, or the customer didn't like the result. I had a knack for doing convergence, which can be one of the most frustrating things to attempt.   The rejuve process used in repair shops that I'm familiar with involves a zapping discharge at the same time as applying heater power. Although it fairly often restores emission, it's only a short term result, and as the emission falls again the tube becomes unusable due to severe smearing.   You could say it was a way to ruin customer TVs prompting another purchase while appearing to be helpful.     NT

Terry Schwartz <tschw10117@aol.com>: Jan 05 07:01AM -0800 The only zapping process I knew of was used when there were shorted elements in the tube. It can't be done with a tube tester -- rather a charged cap. It can restore emissions, depending on what was shorted in the tube. Heater voltage was not required. If it works, the picture is not typically affected. But too often the short cannot be removed. In fact sometimes it welds an intermittent short permanent.   NT: I'm curious as to your understanding of the process you described -- what is the mechanism that would be in play that would increase emissions by zapping it while powered? Emissions are largely a function of the cathode quality (useful remaining life) and unless a zap removes a cathode short, I don't see how it works. Also don't understand how it would contribute to smear, or how the emissions would fall again, unless the cathode was already bad, in which case the emissions would not have recovered at all.   Terry

"pfjw@aol.com" <pfjw@aol.com>: Jan 05 07:07AM -0800 On Friday, January 5, 2018 at 10:01:46 AM UTC-5, Terry Schwartz wrote: > The only zapping process I knew of was used when there were shorted elements in the tube. It can't be done with a tube tester -- rather a charged cap. It can restore emissions, depending on what was shorted in the tube. Heater voltage was not required. If it works, the picture is not typically affected. But too often the short cannot be removed. In fact sometimes it welds an intermittent short permanent.   > NT: I'm curious as to your understanding of the process you described -- what is the mechanism that would be in play that would increase emissions by zapping it while powered? Emissions are largely a function of the cathode quality (useful remaining life) and unless a zap removes a cathode short, I don't see how it works. Also don't understand how it would contribute to smear, or how the emissions would fall again, unless the cathode was already bad, in which case the emissions would not have recovered at all.   > Terry     Agreed.   I have used charged caps on three occasions (two successful) to restore bad coils in field-coil speakers. I have tried it several times without any success to 'save' open transformer windings.   But, otherwise, 'rejuvenation' for tubes has consisted of over-voltage on the filament for varying periods of time and at varying percentages over what is rated - and not much more. And CRT "Brighteners" increase voltage to the filament in my experience as well. Some by a variable (adjustable) amount as well. Perhaps NT is conflating different processes?   Peter Wieck Melrose Park, PA

Fox's Mercantile <jdangus@att.net>: Jan 05 09:28AM -0600 On 1/5/18 9:01 AM, Terry Schwartz wrote: > The only zapping process I knew of was used when there were > shorted elements in the tube.   I have a B&K CRT rejuvinator. I pulled the CRT out of my 1948 Andrea. It tested just below the Green range. Hit the zap-o-matic rejuvinator button. It crept up into the Green range. The third time it fell all the way down to the bottom of the Red range.   Well that settles that. Now it's dead instead of very dim.         -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com

Terry Schwartz <tschw10117@aol.com>: Jan 05 07:53AM -0800 The B&K units and their ilk work exactly that way -- increasing the filament voltage temporarily. They may also change the grid bias during the process - not sure.   Jeff, I suspect your filament is open now.... unfortunate.

Terry Schwartz <tschw10117@aol.com>: Jan 05 08:31AM -0800 Ok, a quick google search reveals that the CRT specific rejuvenators apply a high potential between the cathode and G1. The resulting arcing exposes some "fresh" cathode surface. I'd have to believe the area would be tiny and therefore the fix very temporary. Seems like it would also be prone to throwing cathode debris at the phosphor surface, aperture mask, or gun aperture. Ugh. But now I understand the ZAP reference.   I was familiar with the older method that used general purpose tube testers with CRT adapters. There was no such capability with those that I was aware of -- only raising the filament voltage to overheat the cathode and boil up the emitting surface. Seems like a better chance of lasting results, if the filament survives the process.   Funny because I owned a B&K 467 for a while, but I don't think I ever tried to use it for rejuvenation.

tabbypurr@gmail.com: Jan 05 08:45AM -0800 > But, otherwise, 'rejuvenation' for tubes has consisted of over-voltage on the filament for varying periods of time and at varying percentages over what is rated - and not much more. And CRT "Brighteners" increase voltage to the filament in my experience as well. Some by a variable (adjustable) amount as well. Perhaps NT is conflating different processes?   > Peter Wieck > Melrose Park, PA     The zapping method was standard in the TV repair industry here while CRTs were in use. It only takes a couple of minutes to do.   http://www.thegleam.com/ke5fx/crt.html talks about a pulse of grid current much improving emission. How it works is I gather disagreed on, but it does. The problem is the tube declines after not long, giving a smeared picture.     NT

Baron <baron@linuxmaniac.net>: Jan 05 02:34PM > That > there are no other suspension components that could be getting > stuck? Eric   If you look carefully, you will see that not only does the lens move up/down, but also from side to side. You can get tiny fractures in the parts securing the wires. So it is possible that one side twists slightly and rubs.   -- Best Regards: Baron.

tabbypurr@gmail.com: Jan 04 09:29PM -0800 On Thursday, 4 January 2018 22:14:06 UTC, Jon Elson wrote: > the resistor. I've broken enough over the years to know the inside is > always white for film resistors, and black for carbon composition.   > Jon   Quite. Even in the carbon comp days they weren't made that way.     NT

Murray atuptown <murrayatuptowngallery@gmail.com>: Jan 05 03:02AM -0800 The clay ones sound like the process used in the Lascaux process circa 15000 BC 🧐

Chris <ithinkiam@gmail.com>: Jan 05 09:03AM >> they were actually trying to *extend* the life of batteries.   > Yes, they were trying to extend the life of the battery until the warranty > runs out.   Batteries are not covered under warranty unless shown to be truly defective - not just swear and tear.

Chris <ithinkiam@gmail.com>: Jan 05 09:06AM > slowdown of the CPU performance had no impact on the usability of the phone. > The articles I have read seem to indicate that was how the problem was > discovered by users, the performance of the phone dropped off. No?   Not as I read it.   It was discovered by the developer of a benchmarking program which collated the results of thousands of tests and noticed distinct peaks in results which matched different iOS releases. When he published his findings only then did people become outraged.   Users always complain of slowdowns, but that is hugely subjective and inverifiable.   I can see both sides of the argument. Apple were trying to extend the life of devices' batteries with minimal impact on users, although they did it in a slightly underhand way. They were trying to do the right thing and should have been more transparent about it.

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