1971 AMPEG SVT
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Ampeg of Linden, NJ was sold to the Magnavox company on November 12 1971, where it became part of the Selmer division.
Other 1971 SVT characteristics: "Blueline" silkscreened graphics with detail etched into the metal, two channels, small black "D shaft" knobs with silver tops, black plastic tone adjustment rocker switches, two metal power switches (with at least one black), small round red power light, silver grille cloth, preamp mounted underneath box top, exposed plastic fan, two prong power cord and outlet, fuse, 4 pin XLR speaker cable and jack, four metal cord wraps, black painted chassis, (3) black transformers: power, filament and output, 6550 power tubes, circuit boards, capacitors, CTS potentiometers with metal "D shafts", two vinyl handles, smooth vinyl covering, usually a black painted wooden box, tube chart sticker, manila envelope containing schematic, six rubber feet, eight chassis connector bolts, CTS speakers, 8x10 inch speaker cabinet with unpainted face and metal bullseye logo, three handles and matching dolly, literature.
1971 serial numbers were stamped into the chassis, seen through a "cutout" in the middle of the removable back panel. The cutout was located between the standby switch and the external amp jack. Serial numbers on the speaker cabinet were stamped into a metal plate on the back. Ampeg serial number dating is undocumented and very difficult. Some examples of 1971 SVT serial numbers are 10254x and 10590x. For more precise dating cross reference the serial number with the amplifier's transformer, potentiometer, capacitor and speaker codes.
Component code dating vintage SVT's: As with all vintage gear, the manufacture date is determined by the newest component/date stamp on the unit. On vintage SVT's, we've consistently seen the newest date code on the unit as being the four digit white ink stamp on the large output transformer. The first two numbers indicate the year, the third and fourth numbers indicate which week of that year.
Other codes to determine the manufacture date: The other large power transformer and the adjacent smaller filament transformer should both have six digit codes stamped into the metal. The first three digits indicate the company's personal manufacturing code. Those should be 682, which indicate the Electrical Windings Company. The fourth number indicates the year. The fifth and sixth numbers indicate which week of that year.
Potentiometers are also date encoded. There is a seven digit code stamped into the metal. The first three digits indicate the company's personal manufacturing code. Those should be 137, which indicate Chicago Telephone Supply or CTS. The fourth and fifth numbers indicate the year. The sixth and seventh numbers indicate which week of that year. Capacitors and speakers can also be dated in a similar manner.