CurtPalme.com Home Theater Forum

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Got some "new" used tubes that you are thinking about using?

You can't see any wear on them but you know they're used, and you haven't installed them yet?

Well, I've learned that you can illuminate the face of the CRT with a violet/UV LED light, and it will excite the phosphor
faintly, which will reveal phosphor wear that's difficult or even impossible to see with the naked eye and the CRT
not energized.

It can also be helpful in determining the phosphor color of a CRT that's missing its labels. Red phosphor glows
distinctively reddish, blue glows blue, and green glows sort of an off-white color.

Try it. It works pretty well and it's super cheap and easy.

CJ

wkosmann · Posted: Mon Oct 25, 2010 3:28 pm Post subject:

Please recommend a specific violet/UV LED that one could purchase for this purpose.

perisoft · Joined: 29 Aug 2007 Posts: 2920 Location: Ithaca, NY

That's pretty cool.

If you haven't got access to that, the other option is to take a photo of the tube face in as even light as possible (no flash!), crop out everything that isn't tube face, and use the equivalent of an auto-level function to enhance the visibility of the wear.

If you want to do that, you need to use as little compression as possible on your photo - ideally none - though, since compression by definition will try to remove data you can't see yourself. Usually even with a JPG you can get an idea what's going on, though.

secstate · Joined: 20 Mar 2006 Posts: 720

Interesting, I seem to remember that Greg E. stating that LED flashlights also showed wear patterns more easily. A lot of them are shifted towards the blue end of the spectrum so they may be an alternative if you dont' have a blacklight.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Most any violet LED should work. Or a UV LED, if you can get one.

From what I've seen, using a UV or violet LED to reveal wear patterns is a more sensitive test method than even making a contrast
enhanced photo of the CRT face.

For some reason it seems to be most effective on the blue CRT as well, but it is effective on all colors.

CJ

akajester · Joined: 09 Jul 2008 Posts: 934 Location: Wisconsin

emdawgz1 · Joined: 14 Mar 2006 Posts: 7949

http://www.theledlight.com/UV.html

Spanky Ham · Joined: 22 Mar 2006 Posts: 5643 Location: Comedy Central

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I put a 99 cent violet LED into one of those little keychain LED light cases. How much cheaper can it get?

CJ

Spanky Ham · Joined: 22 Mar 2006 Posts: 5643 Location: Comedy Central

Where did you get it?

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I bought several from a guy selling LEDs at a hamfest.

There's also this obscure place called "ebay" where you can get them really, really cheap, too. They may cost more to ship than it costs to buy a handful of them.

CJ

AaronB · Joined: 05 Sep 2007 Posts: 22 Location: Ottawa, Canada

can't beat 99 cents including shipping and batteries!
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300418632901
The downside: based on experience with various cheap Hong Kong based sellers, I can tell you that it will take roughly 2 to 4 weeks to get your package.