Dating Fender Tube Amps by Serial Number Part 3
Last Updated on Sunday, 20 September 2009 20:42 Tuesday, 05 May 2009 18:19
Dating Fender Tube Amps by Serial Number - Part 3
In part 3, Greg Gagliano details his Fender amp research conducted with Devin Riebe and Greg Huntington.Their research enters its fourth year! You can check out the full article here: Dating Fender Tube Amps by Serial Number - Part 3
The main focus of this article is the speakers found in Fender amps, however, the following will be touched on briefly too:Early silver face amps
There still seems to be some confusion about how to distinguish between a silverface Fender amp that has the desirable AB763 circuit and one that has the less-desirable AB568/AC568 circuit. Part of the confusion stems from the lack of any AB568 or AC568 tube charts. Fender never printed any since there were plenty of leftover AB763 tube charts available and these were used well into 1969.
Transitional circuits
There are some circuits that don't completely match the schematic for a particular model. Leo Fender was notorious for tweaking circuits and the results of some of his tinkering can be found on late examples of an amp prior to the switch to a new circuit. Also, the different component values could be due to a necessary substitution on the production line when a particular value was out of stock.
Oddities
One of Leo's experiments or "one off" custom amps surfaced recently. It's a circa 1955 tweed Tremolux (5E9) that has two factory stock Jensen Hi-Frequency tweeters with a passive crossover between the Jensen P12R and the tweeters. Was Leo was influenced by Magnatone's use of tweeters?
CBS era quality control
The "OA" and "OB" date codes mistakenly stamped on the tube charts of January 1966 and February 1966 amps, respectively, have been discussed in teh earlier articles (and also the misspelling "Division of Colombia Records Division" instead of "Division of Columbia Records Division" on the rear chassis panel on some amps from late 1965 and early 1966).
These mistakes were merely cosmetic. There were quality lapses in the circuits themselves during the CBS years, some of which had serious consequences. Examples of these include ceramic caps used in parallel to achieve the correct value instead of a single cap, change to often inferior sounding "chocolate drop" caps, and incorrectly wired circuits.
Fender Speakers
Unfortunately, Teagle and Sprung's Fender amp book does not have much info on speakers. Greg compiled a list of speakers used in Fender amps and took some photos of some of them as well (see linked article). The list presented is based on the researchers' actual observations, but is not comprehensive.
A New Fender Amp Resource
Mark Ware thought it was a good idea to put together a very informative Fender Amp Field Guide. The site is nicely done and includes descriptions, pictures, and schematics for Fender tube amps as well as other Fendercentric information.