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Marshall JMP 50

This is a 1967 Marshall JMP 50 Plexi. A 50W tube rectified EL34 model transitional between the typically tube rectified Black Flag JTM 50 and the later solid state rectified 1987 models.

Cabinet rear. Cabinet probably has been recovered but using vintage green hue Marshall tolex some years ago.

Requires a Bulgin style power cord.

Back Panel removed.

The JTM 50's were the first to use the output transformers designed for EL34 tubes. The JTM 50 Black Flag typically used the 784-128 OT, some were equipped with the 784-139 OT as the 128 was phased out. This JMP 50 has the 784-139 OT. The power transformer has been changed to a Mercury Magnetics copy of the original, bringing the cost of this amp down to my price range. The paper date stamp sticker has been lost.

V1 is common cathode design. The grey Radio Spares capacitors are likely original to this amp. Innards are in good shape, I only added a bias trim pot.

Close up of the power section.

Another view of the board. All of the electrolytic capacitors on the board have been replaced.

Another power section view.

The 1967 JMP 50 atop a 1970 model 1987 and a 1960AX speaker cabinet loaded with Weber Silverbell and 1230-55Hz speakers.

Unless indicated otherwise, all photographs are by Andrew Leslie.
Copyright © 2017 Andrew Leslie; Webmaster: Elsa Leslie, CABEL; Last Updated: November 1, 2017 11:44 AM