Stock Crack. First Build. 6080 Tube wont glow.

[Audiotechyo]

Hello, I am new to the world of DIY audio and tubes.

My 6080 tube wont glow so I believe there is a problem but I have spent quite a lot of time looking for the issue and have not found the issue. I will post my resistance, Voltage, and build pictures with hopes that I can be helped. The smaller tube looks to be working well and the LED's light up.

I believe my resistance checks out.

Resistance Check
Resistance
Terminal / Actual:
1 / 25.1k
2 / 2.8k
3 / 0 ohms
4 / 2.9k
5 / 25k
6 / 2.5k
7 / 3k
8 / 0
9 / 2.9k
10 / 2.5k
12 / 0
13 / climbs slowly toward 270k ohms
14 / 0 ohms
20 / 0 ohms
22 / 0 ohms
B3 / 3k
B6 / 2.9k
RCA jacks:
Ground lug / 0 ohms
Center pin / R 96k ohms - L 105k ohms

Now for voltage checks. All voltage checks are done using DC mode on my volt meter, with it on the 200VDC setting.

Voltages
Terminal / Suggested / Actual:
1 / 75-90 / 80
2 / 170 / 178
3 / 0 / 0
4 / 170 / 178
5 / 75-90 / 78.7
6 / 0 / 0
7 / 100 / 0
8 / 0 / 0
9 / 100 / 178
10 / 0 / 0.1
11 / 0 / 0
12 / 0 / 0
13 / 170 / 178
14 / 0 / 0
15 / 185 / 197
20 / 0 / 0
21 / 206 / 216 ( had to switch to 500VDC for this one.)

A1 / 90 / 78
A2 / 0 / 0
A4 / 0 / 0
A5 / 0 / 0
A6 / 90 / 80
A7 / 0 / 0
A9 / 0 / 0

B1 / 90 / 79.8
B2 / 170 / 178
B3 / 100 / 0
B4 / 90 / 78
B5 / 170 / 178
B6 / 100 / 178
B7 / 0 / 0
B8 / 0 / 0

 

[Paul Birkeland]

Is the octal socket mounted in the proper orientation?  (See page 13)

 

[Audiotechyo]

How embarrassing, that indead is an issue, I shall rectify it after dinner and report back!

 

[Audiotechyo]

Great news! That was the issue!

Now for the bad news! My power switch is busted, it is currently always on no matter what. Where can I purchase another? I have some 12V 20AMP switches but I don't think they are in spec to work with 110VAC Mains.

 

[Chris65]

http://bottlehead.com/product/replacement-rocker-switch/

 

[Audiotechyo]

Hello All,

For a while my Crack worked really well. Then it started to have a crackle to it. I fliped it over and carefully probed the wires to try and get a root cause but it didnt respond. It was only an issue when there was no signal so I simply ignored it. Today my 6080 Tube would not glow. Luckily I had another RCA 6080 tube that I had wanted to roll eventually. I swapped it in and everything is working great now! However my original 6080 tube barely lasted barely 30 hours, is this typical? The new tube has no crackle either at no signal.

 

[fullheadofnothing]

Installing the tube backwards would have put high voltage on parts that aren't supposed to see high voltage, so may have shortened the lifespan.

 

[Audiotechyo]

Ah that sounds right. Thanks! I have a lot of interesting questions about Tube circuits, are there recommended books for headphone amplifiers and the like? I tried reading my crack circuit but I couldnt tell if there was feedback or not from the manual's Circuit diagram. I feel like Im reading that negitive feedback is bad in tube amps but I would really like to learn from the bottom up.

 

[Paul Birkeland]

The first place to go would be to your local community college.  Take an evening class or two in introductory physics and engineering.  That will help a ton in terms of making sense of anything that you might later read in a book.

Some good (Free) text references can be found here:
http://www.tubebooks.org/technical_books_online.htm#Vacuum%20Tube%20theory%20&%20circuit%20design

 

[Audiotechyo]

Funny enough, I have an electrical engineering degree, I just graduated 2 months ago.

 

[Doc B]

Lots of us have potentially useless degrees here. I have a degree in Physics from Berkeley. I spent an entire 35 minutes one day in my sophomore year doing a lab on vacuum tubes, so I am more qualified than most to run a tube audio business. Check out the link to the tubebooks site. Lots of good info there for someone who has a grasp of the basics.

 

[Audiotechyo]

I sincerely apologize if I sounded boisterous, I actually felt rather disappointed in my inability to truly analyze the circuit from my manual, and I asked my question after seeing another thread where you seeming made some great inferences to impedance changes quickly, it seemed like nothing short of pure experience and I simply wanted to also start to gain experience in tube audio design. I'm fascinated by tubes and older solid state audio but honestly I didn't get a degree from a top school. It's not a fly by night school but hardly anyone's heard of UCF. Basically, I'm very worried that I some how achieved my degree without learning anything. I only even mentioned it so that you would understand that I at least knew the basic physics behind current and voltage. I know how electrons flow and such. Honestly one thing that has always illuded me,bis feed back. What little I know about feedback is with active devices like opamps. How feed back works with tubes or transistor amplifiers is something I have been trying to understand, to no avail. I will be sure and look into those books!

 

[Doc B]

I was just being tongue in cheek. This tube stuff is a dead art. Tube textbooks are ancient manuscripts. We all have to be part archaeologist to get the knowledge we seek. One of the more approachable texts on the subject is the one that Ryder published for training tube era military radio techs. I think it is in that archive, but not positive about that. Why I ever sold or gave away my copy IDK.

 

[Paul Birkeland]

Ah, well, with your degree, plow right into those books.  Morgan Jones also has a popular text that I believe is still in print.

 

[Audiotechyo]

Oh I didnt see this reply till now haha, Ill look into that! Thanks again for all the support!