1B3GT,6CU6, and 24A  vacuum tube. free - Page 1
Forum section: electronics / general

author: whitevamp
author_rank: Regular Contributor
timestamp: June 18, 2017, 11:18:57 pm
content: edit:as richnormand and N2IXK have mentioned it looks like these are 1B3GT, 6CU6, and 24A vacuum tube'si dont know if they are worth any thing or not or if any one wants them. but there still free just pay shipping.--------ok so i have a what appears to be a new tube,and box, with no markings on it and its all yours for free you just need to pay postage, or pickup.was saved from the trash can. i also have a Mogul bi-post base light bulb. if you want that one, as well i'll through it in at no charge..

author: richnormand
author_rank: Unknown
timestamp: June 19, 2017, 01:20:59 am
content: I think this is what you might have here.A high voltage rectifier damping tube from the early TV use of fly-back supply for the crt acceleration voltage.Made by several manufacturers such as RCA, Westinghouse, Sylvania etc... Some were a bit shorter than the standard length.Also, as yours, some had a white/yellow fluorescent coating near the base looking at xrays emitted sideways, if the max voltage or current was exceeded. They would glow a dull green ring in that area.If you look at the photo of one that does not have the coating you see a rolled up plate to avoid hv discharges. The cap on top was the plate and had to be there since the base pins could not deal with the 20kV or so for operation.A quick check for continuity between pins 2 and 7 will tell you if the filament is still good.Cheers.

author: whitevamp
author_rank: Regular Contributor
timestamp: June 19, 2017, 03:08:31 am
content: Quote from: richnormand on June 19, 2017, 01:20:59 amthx for this and yeap indead thats what it is. as i found on the cover of the box 1b3.and yea it has 1.90ohms on pins 2 and 7..and i also have a couple more that i just found. also free.and6cb6

author: N2IXK
author_rank: Frequent Contributor
timestamp: June 19, 2017, 01:31:32 pm
content: Definitely looks like a 1B3GT high voltage rectifier tube. The white band isn't for X-ray protection, but to prevent electrostatic charging of the bulb glass which can lead to punch-through and failure.The 6CU6 is a beam power amplifier tube, designed for use as a horizontal sweep amplifier in B/W television sets.The Cunningham tube looks like a type 24A, an early tetrode type used in radio receivers.

author: whitevamp
author_rank: Regular Contributor
timestamp: June 19, 2017, 01:46:14 pm
content: Quote from: N2IXK on June 19, 2017, 01:31:32 pmthanks for this.also i updated the op, and title of this thread.

author: richnormand
author_rank: Unknown
timestamp: June 19, 2017, 09:50:34 pm
content: Quote from: N2IXK on June 19, 2017, 01:31:32 pmI was servicing TVs in the 60s to pay for my studies and I am pretty sure either RCA or Sylvania had the x-ray emission warning band in them. Not as wide as in OPs photo however, but in the same spot. It just told you the tube was overdriven. Most of them had noting there. Adjusting the trimmer for the horizontal sweep drive would trigger the green glow when the current or hv was too high. I will try to find the spec sheet for one of those and post it. It's been a long time...In early colour TVs, working at insane 25-30kV acceleration voltage, I remember similar coatings on hv regulator and rectifier tubes using a wide coating as shown for exactly what you described, particularly with recessed socketed tubes near the chassis. It would dissipate the possible corona and static. They were typically in brand new TVs and I don't remember if the replacements tubes had them. In a 1B3 I don't remember seeing such a wide band used as such, but very possible.

author: N2IXK
author_rank: Frequent Contributor
timestamp: June 20, 2017, 12:09:40 am
content: I have heard of 6BK4 shunt regulator tubes that would glow green with excessive current/voltage, but never an HV rectifier type. I had assumed that it was just glass fluorescence under electron bombardment, rather than a designed-in warning feature. If you have any further info on this, I would love to see it, and to find an example of a tube that has that feature. The HV regulator tube's glass envelope often turned brown from electron/X-ray bombardment, and used examples as dark as a glass beer bottle are commonly seen.The 1B3 rectifier wasn't used in color sets, as the PIV rating wasn't generally high enough. Color sets usually used a 3A3 or later derivative.If anyone is interested in a real "deep dive" on the humble and once ubiquitous 1B3 tube, a 1960 issue of the "RCA Engineer" covered the development history, and the multiple variants that came out over it's production life. The white banded variant (among others) is discussed in some detail in an article on page 42 here:http://www.americanradiohistory.com/Archive-RCA-Engineer/1960-02-03.pdf

author: richnormand
author_rank: Unknown
timestamp: June 20, 2017, 01:15:15 am
content: Thanks N2IXK,the whole link was great reading.I never saw the white banded variant here at the time (Canada). I do remember the 6BK4 (still have some in the tube caddy) but only in brand new OEM TVs did they seem to have the white band, not as replacement tubes, and, boy, do these early colour TVs needed replacement tubes regularly.... The real easy cash was from the DIY using the conveniently located tube tester display and changing everything that looked "weak"...