Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: firemedic on September 25, 2011, 08:43:56 am
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Out of curiosity I took a look at my SE amp tubes with a thermal imager.
The 5V4 rectifier held steady at @325-350 degrees F.
The 6V6GT was in the 300 degree range around the edges but the center went straight up to over 1200 degrees!
I know, duh. I was curious though.
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I have noticed that some children like to reach in and grab the tubes.
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It's the only way they'll learn. :think1:
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I have noticed that some children like to reach in and grab the tubes.
Some adults around here have on more than one occasion picked up freshly pulled tubes off his bench, but only after he's taken off his OVEGLOVE!
It's the only way they'll learn. :think1:
I hope I learn before I do it again! :laugh:
but the center went straight up to over 1200 degrees!
Do you mean the center like inside the tube? or on the tip top?
Ray
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I think it only took me one time grabbing a rectifier tube that was on only a short time before I got the idea to not do it again! I'm normally a slow learner, but not in that case wow! :cussing:
Regards,
Don
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"Do you mean the center like inside the tube? or on the tip top?"
The TI can't see inside the tube, just the outside of the glass.
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I use a tube sock to handle hot vacuum tubes. I'm just punny that way.
(http://3.bp.blogspot.com/_Lt6Yc4rAb6w/SQ8H5iUH46I/AAAAAAAAB6w/uJ8_KFHQd-E/s400/Socks.jpg)
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She does not always cover her legs, but when she does... she wears dos sockies.
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The 6V6GT was in the 300 degree range around the edges but the center went straight up to over 1200 degrees!
That's hotter than the cathode, and, I think, hotter than the melting point of the glass... measurement error perhaps?
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The upper *safe* limit on receiving-tube glass is 400-425 degree F.
This is a happy fit to economical pin/glass seal technology and to fire-risk ("Fahrenheit 451").
The melting point should be considerably higher; 400F on the bulk of the bottle is 300F at the seals and they give trouble before glass does.
300F on a Power bottle means you are not using it as hard as possible. When I was cooking 6550 at 35W-42W I was getting 375F-410F.
And FWIW my $20 IR reader only went to about 410F; you pay more for higher range.
The plate runs hotter. And I could show higher temp adjacent to the plate, much lower at top or base.
The cathode should be 1000F-1150F. The heater will be hotter. However the glass is nominally opaque to IR waves. And nominally you "should not" be able to resolve a small hot-spot inside a larger bottle; you should read the average of the area. Maybe some glass is not so IR-opaque? Maybe your sensor reads between IR and visible?
What do you see on your soldering iron?
Can you find a clear-glass incandescent and read the filament? It is probably out of range, IF it can read through the glass; otherwise it should read the average which for a hi-watt lamp should be around 400F.
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Uh, it may not be 100% accurate. The TI is designed to find hot spots &/or victims when working in a smoke-filled house. It's sensitive to temperature differentials within the scanned areas, not exact temps. There's a bullseye in the middle which with a temp indicator (0-1200 degrees) up the side of the display telling the user -roughly- how hot the bullseye is. It's pretty cool, you can see IR footprints on the floor when someone walks with shoes on, etc.
The tubes appear all white, dark background. As the bullseye scans across the power tube it goes from 325 to >1200 as the cursor passes over the center of the tube (kind of like a stud finder). It's probably a mistake but still cool. Didn't happen with the rectifier. I'll try to post a picture soon.
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The cathode should be 1000F-1150F.
Oh, I missed the Fahrenheit part. Awful awful ridiculous temperature scale.
Incidentally, cathode temperature is 1050K, or 1430F.