Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Aug Sun 25, 2019 12:13 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 6 posts ] 
Author Message
 Post subject: How to retrieve worn off tube numbers
PostPosted: Apr Sat 02, 2016 12:07 am 
Member

Joined: Apr Thu 16, 2015 11:04 pm
Posts: 439
Location: Sacramento, California
I learned of this trick from a PDF of a 1950 radio magazine that I was looking at for a schematic. If you can't read the number of a tube, rub a pencil "lead" (graphite today) over it, look at it under a light such as a flashlight or desk lamp, and you can see the numbers. Apparently this works because of the way tube numbers were embossed on the glass, leaving an indentation. I used this to retrieve the tube numbers from my Lear 562-more on that in the electrical restoration forum.


Top
 Profile  
 
 Post subject: Re: How to retrieve worn off tube numbers
PostPosted: Apr Sat 02, 2016 10:21 pm 
Member
User avatar

Joined: Feb Thu 24, 2011 3:13 pm
Posts: 916
Location: Ironwood, MI
This is a great tip.

I've tried all sorts of techniques from freezing them, bringing them
out of the freezer and trying to read numbers; black light; breath vapor;
all with so-so results.

I couldn't wait to try this one and, by gosh, it worked! I had to find a
pencil with a very soft "lead." The new pencils all seem to be made of
Chinese crappy who-knows-what and even on white paper make
an anemic gray shadowy line. Pencil grading numbers yielded inconsistent
results so I couldn't really go by what number or HB value was noted.
But I found an old pencil (Jay's Potato chips...remember when they gave those
away?) that makes a really well-defined dark line and it brought the tube numbers through nicely.

Thank you BakelitemanCA for sharing.


Top
 Profile  
 
 Post subject: Re: How to retrieve worn off tube numbers
PostPosted: Apr Sat 02, 2016 11:33 pm 
Member
User avatar

Joined: Sep Mon 16, 2013 2:42 am
Posts: 3384
Location: Tucson, Arizona U.S.A.
Try art pencils rather than office supply pencils. They come in a variety of grades. As long as you stick to the same brand, you can tell if a given pencil is harder than softer than another. But the numbers aren't consistent across brands. You get them at an art supply store.

Jim Mueller

_________________
Jim Mueller


Top
 Profile  
 
 Post subject: Re: How to retrieve worn off tube numbers
PostPosted: Apr Sun 03, 2016 12:20 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 13930
Location: S. Dartmouth MA 02748-1225 USA
A 5 or 7 mini LED flashlight seems to work rather well too.

Chas

_________________
Smith's Ale Gives Strength, Smith Bros. Brewers, New Bedford MA


Top
 Profile  
 
 Post subject: Re: How to retrieve worn off tube numbers
PostPosted: Apr Mon 04, 2016 4:04 am 
Member

Joined: Oct Sun 18, 2015 2:49 am
Posts: 237
Location: San Angelo, TX
Sunlight and a 10 power loupe are a great help especially if you are on the top side of 70!


Top
 Profile  
 
 Post subject: Re: How to retrieve worn off tube numbers
PostPosted: Apr Tue 12, 2016 7:02 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 5722
Location: 253 Blanche St. Plymouth, MI USA
I find a little "face oil" off my forehead brushed onto the glass does the trick 90% of the time. View it under your bench magnifier lamp at various angles. TIP: the markings are nearly always above the KEY of the base, so look there. The KEY of fat pin tubes (6A7, 78, 26, 42, 2B7 etc) is considered between the two fat pins.
After WW2, the marking can be anywhere.
Mark Oppat


Top
 Profile  
 
Post New Topic Post Reply  [ 6 posts ]  Moderator: Chuck Schwark

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB