Dating Technics SL1200's
This is mostly lifted from
wikipedia's SL1200 page with some additions by KAB.
The serial number is generally found on a gray label located either on the back of the deck, or on the bottom.
Old-format serial number: NHOJF20765 (SL-1200 manufactured 1982) The first digit shows the year when the turntable was manufactured. These serial numbers contain no indication of the month of manufacture. It should be noted that serial numbers in this format contain no letters following digits.
New-format serial number: GE4FB001154 (SL-1200MK2 manufactured June
2004 or 1994) The first digit shows the year when the turntable was
manufactured, while the month of manufacture is indicated by the letter
following it. Months are coded as letters between A and L inclusive; A
indicates January, B indicates February, and so on, so F indicates June. This
was deviated in the last year of production where September production used the
letter S for some reason instead of I. The way to tell if it was made in the
90's or the 2000's is to make 2 additional inspections:
1. Check the 3 screws that hold the motor stator, in the 90's these were fine pitch threads, later they were changed to hi speed self tapping threads.
2. Remove the platter and check for a cutout in the chassi in the 9:00 to 11:00 o'clock positions. This cutout also appeared in later models.
In 2009 the interconnect cable was changed to a high capacitance cable which can be identified by the end connector.
There are also at least two other serial number formats that were used by Technics on early SL1200MK2 models. "DA22 17D142" and "MJ7821F287" are examples of serial numbers seen on early production units that both lacked mounting provisions for the internal "bottom base" (Technics part # SFAU122-02) and possessed a different style of dust cover hinges. The old hinge had a receptacle on the back which received the hinge with a thin wide slot. The later and current models feature a hinge receptacle that accepts the hinge with a square opening approx 3/8" square.
In addition to the above, all the SL-1200MK2s from the 1970s and early 1980s have a 4-inch-diameter (100 mm) plate where the RCA and ground wires enter the chassis in the rubber base of the unit. The later models have a smaller hole through which the wires enter the unit. The larger hole size returned in 1997 in the MK4 and 2003 in the M5G models
KAB Electro Acoustics
Plainfield, NJ 07062