View Full Version : 6BK4, Scary green glow.

10-08-2015, 07:53 PM
Was making some fine tweaking to the HV on my CTC-7 since it was about a kilovolt low. After adjusting the HV when I turned the set on and the HV kicked in. An eerie green glow formed at the bottom of the 6BK4 HV regulator in the gap between the anode and the filaments. Scared me a bit. Anyone had this happen to them? Checked it with the geiger counter and the reading was off the charts from about 6 inches away from the 6BK4! :eek:

10-08-2015, 08:01 PM
Normal to glow green.

10-08-2015, 08:37 PM
It's normal I've seen the green glow many times over the years of working on tube type color sets using 6BK4s and similar regulators. The roundie that i'm restoring now the 6BK4 also glows green. As the tube conducts heavier the brighter the glow becomes. Some also glow orange as well. As you lower the brightness or high voltage the glow will get brighter as the tube will conduct heavier.

10-08-2015, 08:44 PM
As long as YOU don't start glowing green, it's alright :)

The set I was working on the other day had a really nifty purple glow from the 1B3. Gassy, I guess, as it was killing the hv. Pretty, though!

10-08-2015, 08:58 PM
Just make sure it's a 6BK4C/6EL4A - the only certified non-xray generating version of the 6BK4. All others (base, A and B suffix) were part of the Xray scare in the late 60s. The 6BK4C was created to fix that problem, and interestingly enough, was invented by a woman....


Eric H
10-08-2015, 09:52 PM
That Patent was filed in 1969, didn't they fix the X-Ray problem long before that?
If not, was there a sharp uptick in Feline Leukemia in the 1960s? (Just kidding, mostly)

10-08-2015, 10:06 PM
More on Janet Deckert, inventor of the 6BK4C and Manager of Glass Tube Engineering at RCA Woodbridge, and an interesting article written by her detailing the invention and improvements in the 1B3GT is here, beginning on page 42.

10-08-2015, 10:23 PM
That Patent was filed in 1969, didn't they fix the X-Ray problem long before that?
If not, was there a sharp uptick in Feline Leukemia in the 1960s? (Just kidding, mostly)

66/67 was the heyday - PF reporter and Electronic Servicing magazine have some skeptic, acceptance and mitigation articles along with GE's ads buying back some HV regulator tubes. Dad had an RCA Communicator magazine dealing with the 6EL4A development (Sylvania and RCA teamed up together, each patented their improvements) that later merged with the 6BK4C tube. I read it as a kid, not knowing of the controversy so much as the "Wow, they didn't stop at the CTC38 chassis in tube development" mentality. At that age, any change to an RCA chassis to me had a huge "WOW" factor.

I remember the article having a staff photo of Ms Deckert - made it easy to find the 6BK4 improvement patent - I couldn't remember her name, but once I saw her name on the patent, I knew I had stumbled upon it.

Is it just me, or could patent art be a nice framed grouping on a wall - take all the good stuff from our childhood and combine it with our passions - patent art from Lego blocks, Play-Doh, Butterfly Yo-yos, Hurst shifters, Space Command remotes, Quasar WID, 6BK4s, and the like and then get archival prints made (after cleaning up the artwork some), and frame them in like frames, and then hang them up in a grouping - kind of a "this is me, in patents" story.....:scratch2: