From robertc90–(at)–ol.com Sun Jan 18 10:20:14 CST 1998
Article: 51415 of rec.audio.tubes
Path: geraldo.cc.utexas.edu!cs.utexas.edu!news-peer.sprintlink.net!news.sprintlink.net!Sprint!newsfeed.internetmci.com!152.163.199.19!portc03.blue.aol.com!audrey01.news.aol.com!not-for-mail
From: robertc90–(at)–ol.com (RobertC908)
Newsgroups: rec.audio.tubes
Subject: Sylvania answer to “Blue Light in Tubes”
Date: 17 Jan 1998 13:51:52 GMT
Lines: 74
Message-ID: <19980117135101.IAA1976--(at)--adder01.news.aol.com>
NNTP-Posting-Host: ladder01.news.aol.com
X-Admin: new–(at)–ol.com
Organization: AOL http://www.aol.com
Xref: geraldo.cc.utexas.edu rec.audio.tubes:51415
The following quote is from a small book by Sylvania entitle “Radio Tube Hints”
volume one dated 1943.
Quote
Three Reason for Blue Glow
Many inquires are received relative to the blue glow which is present in a
number of Sylvania Tubes. Most of these are based on the misunderstanding of
the different types of glow that may be present in a tubes. There are three
different types of blue haze that may appear while tubes are in operation. The
are classed as: Fluorescent glow; Mercuty Vapor Haze; Gas.
The fluorescent glow is usually of violet color, and is noticable around the
inside surface of the glass blub. This glow is a phenomenon caused by
electronic bombardment taking place within the tube. This glow changes with
the intensity of the signal and may at time become quite brilliant.
Fluorescent glow has absolutely no affect on the operation of a receiver. In
fact, tubes with this characteristic are particularly good as regards gas
content.
Mercury vapor haze is a blue glow which is noticeable between the plate and
filament in Types 82 and 82 rectifier tubes. These are the only types of
Sylvania receiving tubes in which this type of haze appears. The perfect
operation of Types 82 and 83 is dependent upon a mercury vapor which comes from
free mercury that has been placed in the bulb during the exhaust period.
Therefore this type of blue haze is in no way detrimental to the operation of
these tubes.
Gas is a blue haze which is usually confined to the vicinity of the plate and
filament structure. Its presence, when of large content, affects the operation
of a receiver to the extent that erratic performance is noticeable. Gaasy
tubes should always be replaced with new tubes.
Testing for the above conditions can be best accomplished by actual operation
in a receiver. It is not necessary to test for the blue glow evident in Type
82 and 83, since this is characteristic of these two tubes.
When in doubt as to the blue content of other types of tubes a sure test can be
made by using a strong magnet next to the blub. A gaasy tube will not be
affect in any way by the presence of the magnet, while the fluorescent glow,
which has no affect on the performance of the tube, will shift about as the
magnetic filed is shifted.
Unquote
The above blue glow explanation is Sylvania’s and is for your information.
It is not to rebuke anything someone else has stated.
Also if your are interested here is the table of contents for this volume of
Radio Tube Hints. This is the only volume I have according to the cover there
must have been additional volumes.
Table of contents:
Converter Tube Design Features.
Three Reason for Blue Glow
Tuning Indicators Type 6E5 va Type 6G5
Tube Mysteries Explained
Type 35Z5G and Type 35Z5GT Trouble
Tracking Down Grid Emission
Filament Grid Short Circuits
Plate and Screen Dissipation Ratings
Service to Servicemen
Bob, W4RLC (formerly WA7OGU)
