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 Post subject: Reading unreadable tube numbers by UV light
PostPosted: Oct Sat 03, 2020 5:16 pm 
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Location: Wood River, Ill.
This may have been posted before, so please forgive me if it has.

I had one of those You Tube popups this week regarding this subject. In it they were suggesting using UV light to read a tube number that was otherwise un-readable. I thought I would give it a try using one of those UV flashlights that are typically used to detect pet urine. Since I already had one, I thought I would give it a try. It works! I had to turn off the shop lights to see it, but it does work. I had tried everything else, and never could decipher the marking.

One tip, though; Do Not Leave the Batteries in the flashlight! Ask how I know!!!!

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 Post subject: Re: Reading unreadable tube numbers by UV light
PostPosted: Oct Sat 03, 2020 6:20 pm 
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Joined: Aug Tue 28, 2018 9:22 pm
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Location: Sanford Fla 32771 (USA)
I have couple of tubes I have tried various methods, breath condensation, freezer method, pray to the tube gods, and some methods have worked on most tubes, but a particular tube, nothing so far. So I tried the UV light since I had one of those lights, in a dark room but no luck. Tried different angles of UV light and viewing.
Any suggestions on position and viewing angles ?
For this RCA tube it is just a challenge befor I discard it.


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 Post subject: Re: Reading unreadable tube numbers by UV light
PostPosted: Oct Sun 04, 2020 2:02 am 
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Paul,

I used it on a RCA 6D6 that simply was un-readable. I tried all the methods you tried, and nothing worked for me, so I thought I would give this method a shot. You do have to position the light just right, otherwise it does not come up. Perhaps there were various methods of marking tubes that has changed over the years? Who knows??? Either way, it's worth a shot, if you have one of the flashlights available, but I don't think I would go out and buy one.

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 Post subject: Re: Reading unreadable tube numbers by UV light
PostPosted: Oct Sun 04, 2020 4:16 am 
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Location: Sanford Fla 32771 (USA)
Quote:
but I don't think I would go out and buy one.

No, I already have a couple of UV lights. And they sure do show up urine stains.


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 Post subject: Re: Reading unreadable tube numbers by UV light
PostPosted: Oct Tue 20, 2020 2:23 am 
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Location: Rochester NY USA
LED flashlight has worked well for me.

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 Post subject: Re: Reading unreadable tube numbers by UV light
PostPosted: Oct Fri 30, 2020 8:41 pm 
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Location: Highland & Livonia, MI
I've lucked out salvaging a number of tubes by using a high-powered stereoscope (up to 40X) and an array of lighting conditions. Markings that are for all practical purposes invisible become faintly visible at high magnifications under the correct light.

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 Post subject: Re: Reading unreadable tube numbers by UV light
PostPosted: Jan Mon 18, 2021 1:54 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Cedar Rapids, Iowa, USA
One time I tried taking my tubes out into direct sunlight while the sun was high. When I held them so that the sunlight reflected off the bulb away from me, I could make out faint markings on a few of them.

John


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 Post subject: Re: Reading unreadable tube numbers by UV light
PostPosted: Jan Mon 18, 2021 11:14 pm 
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Location: N. Palm Bch, Fl.
I've been using that trick for a while. Sunlight is so much better then artificial light and the eyes aren't what they use to be. Trying to follow black, brown,green wires in a cluttered chassis and the colors seem to blend together. Outside in the sun light they all become clear.

Freeman


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 Post subject: Re: Reading unreadable tube numbers by UV light
PostPosted: Jan Wed 20, 2021 1:37 pm 
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Location: Sunbury, Ohio 43074
Off topic a bit and don't want to hijack, but a tip: Use a daylight color temperature color LED "fluorescent" bulb on your bench. Makes a world of difference to "more mature" eyeballs. I got a 4' shop light that was LED to start... next I might just modify and old flourescent fixture for newer LED bulbs. 5000 degree K is about right.

As for tube markings .... it's all in the light and the angles. In some cases combined with the cooling trick as well. I wonder if Collings, then using UV light, makes any difference. I'd always thought that the cooling was simply a gentle way to allow condensation on the glass ... much like just breathing on it but better, and sustained for a minute or two till it warms up.

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Last edited by Barry H Bennett on Jan Thu 21, 2021 2:49 am, edited 1 time in total.

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 Post subject: Re: Reading unreadable tube numbers by UV light
PostPosted: Jan Thu 21, 2021 1:04 am 
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Joined: Dec Sun 06, 2020 10:33 pm
Posts: 221
Location: Waterbury, CT. 06704
Good to know.
I just bought one of those lights from Ollie's for $3.99. I had a 15% off coupon that was about to expire and they sometimes have little do-dads really cheap so I looked around. Something told me that light might be useful so i bought it. now I'm glad I did because I have a few tubes that the markings are gone. Thanks for the tip.

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