The 5D6 was a major departure from the earlier 5B6 Fender Bassman model.Designed by Freddie Tavares, longtime R&D man at Fender, Instead of the single 15" speaker, four 10" Jensen Alnico P10R speakers were used.
The following chart, was originally printed in VG magazine, by Gerald Weber.
If you see any data that is not listed here or notice any errors, for 1970’s and earlier Fender amps, please send us an email and we will update the chart.
During the different eras the Bassman amp came in many different shapes and configurations.
Few other models experienced so many changes in terms of looks and tone.
Other things to look for include chasses placed in cabinets from a different year, “doctored” tube charts, non-original control plates (usually reproductions) on silverface amps, original transformer bell ends (they have correct date codes, of course) on non-original transformers, and non-original knobs (either repro or silverface knobs on blackface amps).unusual things can be found such as the empty “Pulse Adjust” hole on the rear of early ’60 brown amps, the “middle” volume control, use of tweed style grill cloth, strange non-documented transitional circuits, and changes in tolex color including the super-rare cream colored “brown” tolex that is found on some late ’60 amps. Given that people may refer to this information seeking specific production quantities of amps they are curious about, it should be pointed out that the serial numbers apply to chassis types, and not specifically to amplifier models.
Looking at serial numbers next to the ’60 5G5 brown Pro Amp for example, we see numbers ranging from 00001 to 02000, suggesting that there are 2000 of these amplifiers made in ’60.
At the Fender factory they used old tube charts when new models came, probably because the tube layout was the same.
Determining production date by serial number and transformer codes is better, and you should also inspect the circuit to be completly sure.
Remember, your amp is newer than the newest component.