Marshall jtm 45 dating
Model 1961 was essentially the lead version of the Model 1987 JTM 45, fitted with tremolo and installed into an open backed speaker cabinet, while Model 1962 was the bass version of the JTM 45 (Model 1986), also fitted with tremolo and open backed cabinet.The output of a typical Bluesbreaker was only about 35 watts, and thus the sound would break up at more moderate volumes as compared to larger amplifiers.
Little did they know then that they were at the threshold of a rock 'n roll revolution... This two piece setup, the head and cabinet, were sold together as Model 2059.However, the 100 watt PA amps used JTM100 faceplates. First, the plexi Superlead and Superbass backplates were introduced, then the so-called Black Flag J. The first prototype is reported to have used four 6V6 output tubes and a single GZ34 rectifier tube.It probably used only one Radiospares Deluxe Output transformer, reportedly giving an output of 60 watt.These amps run at much lower voltages than the later KT66 amps, producing less power while being easier on the tubes.
Also, it should be kept in mind that the voltages drop or sag significantly under load, since the power transformer was only rated for 200m A (by comparison, a Twin transformer is 450m A).
Sadly, Jim Marshall, the Guv'nor, passed away on april 5th 2012. These amps were built as heads (or tops) separated from the speaker cabinets. These amps were introduced in april 1981, around the same time as the JCM800 series.