The simplest vacuum tubes resemble incandescent light bulbs in that they have a filament sealed in a glass envelope which has been evacuated of all air.
2006 amps have a small metal “Fender 60th Anniversary” button on the back plate. Early Tweeds The early green board tweed-covered amps were not lacquered. It has the same cream board inside with the same components as every other current-production Blues Junior.
The serial numbers for these amps begin with “LO,” indicating that they were made in the Fender/Sunn Lake Oswego factory. It usually applies to old vacuum tubes/valves that have gone unsold for decades. All cream board tweed Blues Juniors have a “Limited Edition” plaque on the back.
The electrodes are attached to leads which pass through the envelope via an air tight seal.
On most tubes, the leads are designed to plug into a tube socket for easy replacement.
The cream-colored board is laid out entirely differently (and better) than the green board. But the old ones sound darker, while the new ones are brighter, with more emphasis on treble tones.
One is not necessarily better than the other; the dark tones are nice for blues and jazz, while the new amps do brighter tones better.
I would have to collect data for ALL the amp types, just to work out how many were made of mine.
Then I became aware of the amazing work Greg Gagliano had been doing since the 1990s - the summary of his latest results are here - and that his research stopped just before the Rivera-era. However for this range of amps at least, I reckon it's not just a policy of withholding company-confidential information. It's no criticism of Fender to suggest that they were too busy making great amps to keep records just so some amateur can use them thirty years later.
However, tubes are still used in several specialized applications such as guitar amplifiers (also called a valve amp outside the U.
S.) and high power RF transmitters, as a display device in television sets and in microwave ovens.
latest updates; small changes to a few amp batches dates, Dec 2015, Feb 2016, July 2016, Sep 2016, March 2017 small changes to 4 amp batches, Nov 2015 typos found, two edits, thanks Ben H, June 20 info updated, totals unchanged Oct 2014 really nifty table design Aug 2014 small data and totals updates Jan 2014 (info updated In 2002 I acquired a Princeton Reverb II. Fender don't part with that kind of information*, so as part of the website I developed for this amp's care and feeding, I put out a call for serial numbers.