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Marshall JTM 50 Black Flag

This is one of the rare JTM50 Watt Black Flag (reverse logo) plexi panel Marshalls. Many of these were tube rectified, this example is diode rectified.


Cabinet rear.

Transformers are original and are Drake. OT is the later 784-139 (earlier JTM-50s typically had the 128 OT) and PT is a 1202-133. The 133 puts more than 500V to the power tube plates with modern line voltage as opposed to the 118 transformer's 430-450V. One cap can has been replaced.

Closer look. Bulgin mains interface.

Closer look at preamp side.

Some electrolytics have been replaced. Circuit is a shared cathode on V1. 100 pf bright cap on volume pot.

Bias capacitors have been replaced. Output capacitors are 0.1 uF (JTM45 style) which really gives this beast a lot of thump. No grid resistors are present. I did add a pair.

Picture of entire board. The amp is very quiet until you put a signal into it.

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