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Marshall Model 1987

This is a 1974 PCB 50 Watt USA export model set up for 6550 power tubes. My first vintage Marshall.

This is a "big box" Marshall 1987 in decent shape but a bit scuffed. The face has been drilled and a PPIMV master volume installed some time ago by the Marshall dealer according to the seller. The sound, to say the least, was a bit disappointing.

Rear of Cabinet.

Rear of Cabinet with back panel removed. The 6550s were removed and a matched pair of Siemens (RFT) EL34s installed.

Top of chassis. A bit of corrosion on the chassis and light surface rust on the transformers. Seen on many vintage amps in the humid south.

Chassis front view. The master volume knob is at the far left, drilled right through the 'JMP' stencil.

Chassis rear. The impedance selector was loose so I hard wired the output for 8 ohms and archived the selector pin. Original filter caps. Preamp tubes are vintage GE's.

Gut shot of the high voltage section. The bias caps were shot and were replaced. The board is loaded with those wonderful mustard caps. Note that the PPIMV master volume was installed by the Marshall dealer without shielded wiring. More later.

Input side of board. All components seem stock. The speaker jacks look original but are not the traditional Marshall jacks.

Some of the mustard caps have cracked epoxy but test and sound fine.

The PPIMV pot that was installed is interesting. It is installed like the typical Type II PPIMV with the 220k mix resistors removed. But that's where the similarity ends. The smiley faces are a nice touch. Codes on the pot are blacked out too. But the pot is a dual 100K audio taper with something like 85k dual taps and with two 500pf caps installed. There are no 2.2M resistors and no shielded wiring. I really have no idea of the logic behind this setup. The amp sounded very thin and fizzy. This pot was removed and the traditional Type II layout installed. After addressing some lead dress issues, this amp now really sounds like I expected.

This Avatar open back cab with a 50w Weber Silver Bell and Blue Dog is a great match for this amp.

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