1974 AMPEG SVT
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During 1974 the power cord and power outlet changed from two prong to three prong.
Other 1974 SVT characteristics: "Blackline" silkscreened graphics, two channels, small black D shaft knobs with silver tops, black plastic tone adjustment rocker switches, two metal power switches, small round red power light, silver grille cloth with plastic badge logo, preamp mounted underneath box top, fan, Magnavox manufacturing, serial number sticker on back panel, 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", vinyl handles, vinyl covering over black painted wooden box, tube chart sticker, manila envelope containing schematic, six rubber feet, eight chassis connector bolts, CTS speakers, "tilt back" 8x10 inch speaker cabinet including two recessed metal handles or "towel bar" handle, both with casters and plastic bullseye logo, literature.
1974 Ampeg serial number dating is undocumented and very difficult. 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, the newest date code on the unit is usually the four digit white ink stamp on the large output transformer. The first two numbers indicate the year, the third and fourth numbers indicate the production week of that year. Example: 7405 means a transformer made in the 5th week of 1974.
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.