ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
UL 508A SPACING
by ale348 - 03/29/24 01:09 AM
Increasing demand factors in residential
by tortuga - 03/28/24 05:57 PM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
1 members (Scott35), 369 guests, and 17 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 2 of 2 1 2
Joined: Jul 2003
Posts: 394
B
Member
When I moved last year,there was no place for some of the old radio gear so it went in the junk. I did try and auction some but freight was prohibitive. I had an old commercial two way that used lighthouse triode final output tubes. The power supply used mercury vapor rectifiers that put out 2000 volts at 1/4 amp. It would light up a whole room then it was keyed.

Joined: Jan 2003
Posts: 1,429
L
LK Offline
Member
My first build project was a CW that used a No. 80 I worked more stations with that home built then any unit since. Most of the tubes I used came from the junk pile. Today this would be a pile of gold.

Joined: Nov 2002
Posts: 794
Likes: 3
W
Member
Just imagine a GCFI using vacuum tube technology..... :-)
Or a smoke detector....

Actually, given that they want you to replace smoke detectors every ten years, some vacuum tubes could last that long in continious use.

Joined: Jan 2003
Posts: 4,391
I
Moderator
OK tube guys I have a question, why do the tubes get more "purple" as the load goes up?

When I was about 16 I had agreed to provide a PA for a party, what I rigged up was a pair of I believe Stromberg-Carlson 200 watt tube amps.

I used one for each channel and drove 4 speakers off of these no problem with a lot of volume. These amps had 4 ohm to 49 ohm (70V) outputs.

While in use I noticed that as the Bass hit the tubes color seemed to change.

Also

A nice set up I saw when I was about 5 or 6 was a tube radio set I think it was made by Scott and it was in separate chromed components, a distant Vermont farmer cousin had it in his living room and used it daily, even then I knew it was something cool.

Dose any of this make sense?

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Joined: Sep 2001
Posts: 806
N
Member
A colored glow inside a vacuum tube can have 2 different causes. Residual gases inside the envelope usually cause a bluish/white glow INSIDE the plate structure, caused by the electron streams ionizing the gas molecules. This kind of glow is a pretty strong indication that the tube is shot, and generally causes some kind of defect in circuit operation.

A purplish blue glow on the inside of the glass envelope is often seen in power tubes, particularly those operating at higher voltages. This is not a cause for concern, and can actually be an indicator of better than normal vacuum. The cause are stray electrons hitting the envelope, where they cause trace impurities in the glass to fluoresce. Because the intensity of the electron beams inside the tube varies with plate current, the position and intensity of the glow will "dance" with the signal being amplified. In an audio amp or modulator, you get a nice little "light show" effect. [Linked Image]

Some types of tubes (voltage regulators, gas/mercury rectifiers, thyratrons, ignitrons, etc.) contain various gases which will emit a characteristic glow during normal operation. The color depends on the fill gas, with argon producing a violet glow, mercury vapor giving a hazy blue, xenon a white/blue glow, and neon the famous orange-red.

[This message has been edited by NJwirenut (edited 09-01-2003).]

[This message has been edited by NJwirenut (edited 09-01-2003).]

Joined: Aug 2001
Posts: 7,520
P
Member
The glow produced by the OB2 voltage stabilizer (cold cathode) I always find rather attractive!

Another thing you might notice inside the glass envelope of some tubes is a metallic-gray looking deposit at some point. This is quite normal and a consequence of the way the tube is manufactured.

A milky-white deposit on the inside of the glass, however, is a bad sign, and generally indicates a leaky seal, rendering the tube useless.

There are a few tube testers on this link, along with plenty of other test equipment:
http://www.thevalvepage.com/testeq/testeq.htm


[This message has been edited by pauluk (edited 09-02-2003).]

Joined: Apr 2002
Posts: 2,527
B
Moderator
I remember building a tube tester in kit form from Allied Radio. I thought it was the coolest thing in the world for having a tapped filament transformer good from 1.5 to 117V(!)

It was handy too, for having an number of military tube numbers, and you got to use a piece of solder to jumper plate and grid connections on a few.

Joined: Jan 2003
Posts: 1,429
L
LK Offline
Member
first project was a VTVM Kit then on to the Tube tester kit. I wonder what that transformer would cost today. reworking an SCR522 was a real trip, and they were a real night show, and provided heat for the cold winter nights.

Joined: Sep 2001
Posts: 806
N
Member
Quote
Another thing you might notice inside the glass envelope of some tubes is a metallic-gray looking deposit at some point. This is quite normal and a consequence of the way the tube is manufactured.

A milky-white deposit on the inside of the glass, however, is a bad sign, and generally indicates a leaky seal, rendering the tube useless.

That metallic deposit is called a "getter flash", and consists of barium or other reactive metal. Intended to adsorb any stray gas molecules which survived initial pumpdown, or which might be liberated from the internal elements during the life of the tube.

When the tube develops a crack, the oxygen in the air reacts with the getter to form a white deposit of barium oxide.

Flash getters are deposited on the inside of the bulb by heating an internal metal "pellet" with an induction heater just after the tube is sealed off from the vacuum pump. The support that once held the getter pellet is visible just behind the getter flash. It often looks like a metal ring or bar.

Internal anode transmitter tubes used a different gettering scheme. They used a tantalum/zirconium alloy for the anode material, which adsorbed gases quite strongly when in operation. The gettering operation required the anode to operate at a red-hot temperature, though! Such a tube will quickly develop gas unless operated at sufficient dissipation levels.

Page 2 of 2 1 2

Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5