No, glass is opaque to far IR, so those will only measure the temp of the glass envelope, not the anode itself. You'd need a valve with an exotic envelope transparent to far IR.
The valves I have examined all had wall thickness less than 1.5 mm, so I estimate a vacuum of about (-) 0.1 bar.
TV tubes go down to about (-) 0.95 bar or even more.
The important thing, I think, was contamination.
TV tubes go down to about (-) 0.95 bar or even more.
The important thing, I think, was contamination.
At least the meter will tell the surface temperature.
At the same time other parts of the chassis can also be checked for temperature rise due to sunlight.
At the same time other parts of the chassis can also be checked for temperature rise due to sunlight.
Not disagreeing on the principle which is a physical fact, but on the scale and effect.
A few degrees? ... no doubt.
100 C or higher?
Sounds too much; anyway measurements will tell.
Will that rise affect/damage tube?
Don't think so.
Tubes survive replating unless it's too prolonged, think hours or days.
Have I ever seen tube plate get red-hot by simple Sun exposure?
No, and very much doubt such thing can happen.
Not to that degree.
True in theory but common place blue tube glow tells me that some gas still remains.
Read somewhere that in tube factories they do not strive for "perfect" vacuum but"good enough"
And in any case plates may gas out something, much later in their life,inside user's device at-home.
Going by the wall thickness, where the outside air pressure would have to be withstood by the material...I think that my estimate is reasonable, the front of a 20 inch picture tube was about an inch thick, and even the necks were quite thick in section.
EL84 is less than 1 mm thickness.
The equations for strength to withstand crushing pressure exist, but I do not have the time to collect all the data, and give the results. In any case, it will be in a range, as quartz glass is much stronger than other types.
The original post was about a valve amp giving distortion after being exposed to sunlight, and reversible problem...means some part is affected by sunlight (photons), or heating up.
OP has not told us tube types, after being asked, so let us wait for more data instead of arguing about the vacuum level inside tubes, where you will agree that Chinese tubes may not be as good as European or Soviet tubes.
USA, GE and RCA were good in their day.
EL84 is less than 1 mm thickness.
The equations for strength to withstand crushing pressure exist, but I do not have the time to collect all the data, and give the results. In any case, it will be in a range, as quartz glass is much stronger than other types.
The original post was about a valve amp giving distortion after being exposed to sunlight, and reversible problem...means some part is affected by sunlight (photons), or heating up.
OP has not told us tube types, after being asked, so let us wait for more data instead of arguing about the vacuum level inside tubes, where you will agree that Chinese tubes may not be as good as European or Soviet tubes.
USA, GE and RCA were good in their day.
Many years ago, the rumor in amateur circles was that the vacuum in receiving valves was pulled down to better than the vacuum between The Earth and the Moon, but some disputed that. Keeping that vacuum, with multiple metal to glass seals, is another whole story. Eimac used Uranium glass around the seals, for its lower expansion with temperature, and spec'd heat radiators (with fins) for the external metal bits to moderate seal temperature.
There's no direct way to measure vacuum in a random valve in hand, without letting the magic escape, but grid current can be measured directly with semi-ordinary (I've got two! for a future project, total cost less than US$50) instruments.
Also, I find it very hard to believe that we could measure, let alone actually hear, any effect of sunlight on an ordinary vacuum valve not designed for the purpose, and not at all for sunlight on the anode. Maybe, but I'm very very skeptical.
All good fortune,
Chris
There's no direct way to measure vacuum in a random valve in hand, without letting the magic escape, but grid current can be measured directly with semi-ordinary (I've got two! for a future project, total cost less than US$50) instruments.
Also, I find it very hard to believe that we could measure, let alone actually hear, any effect of sunlight on an ordinary vacuum valve not designed for the purpose, and not at all for sunlight on the anode. Maybe, but I'm very very skeptical.
All good fortune,
Chris
Mundane reason may be transformer or other bits in power supply getting warmer...but I think New Zealand does not have the intensity of sunlight to cause that much of an issue...
A couple of silly reasons / incidents come to mind:
1. If it is sunny, power supply grid is less loaded, so mains volts goes up enough to cause issues...
2. Man goes to car dealer, says car will not start if I get butterscotch (IIRC) ice cream, but other flavors, including chocolate chip do not cause this.
They were mystified, took the carburetor apart, all was normal.
So they took the car to the ice cream warehouse / large shop, sure enough it happened.
Then they realized that butterscotch was in a different building, and took 10 minutes to deliver, enough for the car to develop vapor lock in the Texas heat!
Anyway OP is mute, so wait a bit for him to pipe up.
A couple of silly reasons / incidents come to mind:
1. If it is sunny, power supply grid is less loaded, so mains volts goes up enough to cause issues...
2. Man goes to car dealer, says car will not start if I get butterscotch (IIRC) ice cream, but other flavors, including chocolate chip do not cause this.
They were mystified, took the carburetor apart, all was normal.
So they took the car to the ice cream warehouse / large shop, sure enough it happened.
Then they realized that butterscotch was in a different building, and took 10 minutes to deliver, enough for the car to develop vapor lock in the Texas heat!
Anyway OP is mute, so wait a bit for him to pipe up.
Cool story, and good reason to stay humble when troubleshooting. Another, about a company in Chicago making hotdogs IIRC. Built a new modern streamlined plant, tried to keep all processes to their time-honored tradition, but something was not quite right, maybe wrong color or something subtle, but important. Eventually discovered that their streamlining had removed a step - somebody in the old plant had needed to walk the product between two buildings, a 15 to 20 minute trip, during the cooking process. Rest period added, problem solved. Reminds me to stay humble, stay hungry.
All good fortune,
Chris
All good fortune,
Chris
Yes, there's often/always? some aspect ignored as unimportant which confuses experiment results.
A Chemist once mentioned a mystery: a certain "simple" reaction, at room temperature, normal atmospheric pressure, worked twice as fast or better inside a certain plastic bucket than on any other, same type, all "twin brothers".
Much later he found, reading old Lab notes, that once a Mercury thermometer had broken inside it.
Apparently tiny mercury remains, adsorbed or absorbed in bucket walls, were acting as a catalyzer.
A Chemist once mentioned a mystery: a certain "simple" reaction, at room temperature, normal atmospheric pressure, worked twice as fast or better inside a certain plastic bucket than on any other, same type, all "twin brothers".
Much later he found, reading old Lab notes, that once a Mercury thermometer had broken inside it.
Apparently tiny mercury remains, adsorbed or absorbed in bucket walls, were acting as a catalyzer.
I have my own very recent lesson in humility. Replacing the mains transformer in an H.H.Scott 299 earliest version for an acquaintance (and also for money - not a fun gig). Found a (used, of course) replacement, terrible shipping as always, but seemed OK on the curve tracer* except that the high voltage leads looked very strange - two were colored identically and the third had a stripe (as usual) - but I/V curves were very different between the color coded halves of the HV secondary. Because I know-it-all, ignored this as unimportant and installed.
Bringing it up on a Variac, B+ approached +500 VDC at half mains voltage. Much head scratching later, realized that the factory color codes on the previously factory installed mains transformer were deceptively wrong, with the striped wire actually one of the HV ends. Someone at the factory must have discovered this (or it couldn't have been sold), fixed the immediate situation without correcting color code and gone home to dinner.
I, who knows everything!, especially color codes, didn't believe the evidence of my own curve tracer, and paid the price for my hubris. Several hours for this one.
* Everyone needs an I/V curve tracer, sometimes, as I've recently learned, called an octopus. Everyone. A filament transformer, a resistor, a couple wires, maybe some nice probe ends - viola.
All good fortune,
Chris
Bringing it up on a Variac, B+ approached +500 VDC at half mains voltage. Much head scratching later, realized that the factory color codes on the previously factory installed mains transformer were deceptively wrong, with the striped wire actually one of the HV ends. Someone at the factory must have discovered this (or it couldn't have been sold), fixed the immediate situation without correcting color code and gone home to dinner.
I, who knows everything!, especially color codes, didn't believe the evidence of my own curve tracer, and paid the price for my hubris. Several hours for this one.
* Everyone needs an I/V curve tracer, sometimes, as I've recently learned, called an octopus. Everyone. A filament transformer, a resistor, a couple wires, maybe some nice probe ends - viola.
All good fortune,
Chris
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No, it wasn't. The OP said that he feels some differences in sound, depending on UV light. He didn't even say that there's a difference for sure. I'd say it's nothing else than expectation bias. Not worth any serious discussion.
Best regards!
glass already blocks almost all UV. try getting a tan in a greenhouse!
unless you have a transmitting tube made out of pyrex, there isn't gonna be UV going into the tube.
You tubes might be a bit gassy in which case any light entering the tube will effect it possibly... like a neon bulb.*
other than that, it probably is just placebo... I myself don't mind the sunlit tone 🙂
*Does your amp maybe have a regulator tube? those will be effected by externernal light. changing their regulating voltage a bit... and also making them strike faster although that shouldnt be a problem.