Marshall JTM50 Schematics

In 1966 Marshall switched to EL34 tubes. To reflect this the JTM45 panels were changed to JTM50 panels. The GZ34 rectifiers were phased during this time. This wasn’t a sharp transition so there are JTM50’s with a GZ34 rectifier. There are even JMP 50W models with a GZ34 rectifier. Schematically these amps are very very similar to the JTM45 amps.

In the first half of 1967 the JTM panels were dropped all together and the JMP panels were introduced. So the JTM50 amps were in production for less than a year from 1966 to 1967.

1961 JTM50 Lead, 50W 4×10″ combo

This amp used the 1987 tremolo chassis in a 4×10″ combo cabinet.

1962 JTM50 Bass & Lead, 50W 2×12″ combo (Blues Breaker)

This amp used the 1987 tremolo chassis in a 2×12″ combo cabinet.

1963 JTM50 Super PA, 50W head

This amp had 4 channels and 8 inputs.

1985 JTM50 PA, 50W head

This amp had 2 channels and 4 inputs. It was the PA version of the 1987.

1986 JTM50 Bass, 50W head

This amp had 2 channels and 4 inputs. It was the Bass version of the 1987.

1987 JTM50 Lead, 50W head

This amp had 2 channels and 4 inputs.

1987T JTM50 Tremolo Lead, 50W head

This amp had 2 channels and 4 inputs and a tremolo.

1989 JTM50 Organ, 50W head

This amp had 2 channels and 4 inputs. It was the Organ version of the 1987.

1960, 4×12″ 75W cabinet

By 1965 the 1960 cabinets were rated as having a maximum power handling of 75 watts. This increased power handling was probably due to the four 12″ Celestion ceramic speakers fitted in these cabinets. These were probably G12-20 Greenbacks.