1973 AMPEG SVT
For photos, click on the links below:
The 8x10 inch speaker cabinet added a slant to the the top back, now including two recessed metal handles and caster wheels for "tilt back" transport. However some 1973 cabinets still used the "flatback" design, including three vinyl handles and matching dolly. The bullseye logo transitioned from metal to plastic. The "Blueline" silkscreened graphics transitioned to "Blackline" and were no longer etched into the metal.
Other 1973 SVT characteristics: 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, preamp mounted underneath box top, exposed plastic fan, two prong power cord and outlet, fuse, Magnavox manufacturing, serial number stickers on the back panel right side and inside the box, 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, chrome sheet metal plate mounted to inside bottom of box, six rubber feet, eight chassis connector bolts, 8x10 inch speaker cabinet with CTS speakers, literature.
Ampeg serial number dating is undocumented and very difficult. Some examples of 1973 serial numbers are 2501x and 2914x. 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: 7323 means a transformer made in the 23rd week of 1973.
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.