Drew's Geezer Amps - Marshall JMP 50

Home
  Fender
   Bandmaster 6G7 1960    Bandmaster 1967 Combo    Bassman 1958    Champion 600 1952    Champ 5D1 1954    Champ 5D1 1955    Concert 6G12 1960    Deluxe 1951    Deluxe 1965    Deluxe Reverb 1965    Pro 5A5 1951    Pro 5G5 1960    Super 5G4 1960    Super 6G4 1960    Super Reverb 1964    Vibrolux 5F11 1956    Vibrolux 6G11A 1962   Fender Kits and Builds
   Bassman 5F6A Hatcher    Bassman 6G6 Build    Champion 600 Reissue Rebuild    Deluxe 5E3 Weber    Princeton 5F2A Weber    Super 5F4 Weber   Marshall
   Bluesbreaker Reissue    JTM 45/100 Super    JTM 50 Black Flag    JMP 50    Model 1960B Cab    Model 1987    Model 1987 Smallbox   Marshall Kits and Builds
   JTM45 Build    Plexi 1987 Hatcher Leslie 120 Speaker Silvertone 1483

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