Marshall

JMP 1986 – 50W Bass Head – 1975

Serial Number: S/A 1473G

Inspection Sticker Date: 21/04/1975 – 21st April 1975

A superb example of a 1975 Marshall JMP 50 Bass Model 1986, presented in very good original condition and retaining its original transformers, choke and much of its original circuitry.

Handwired and dating from Marshall's highly regarded mid-'70s JMP period, the Model 1986 is the bass-voiced counterpart to the legendary 1987 Lead, offering a warmer, fuller response with a thicker low end and smoother high frequencies.

Although originally designed for bass, these amplifiers have long been favourites among guitarists looking for rich vintage cleans, thick, harmonically complex overdrive and exceptional dynamic response.

This example is particularly appealing thanks to its original iron, period Mullard mustard capacitors and exceptionally well-preserved original cosmetics.

Chassis & Originality

• Original Drake 1202-164 mains transformer

• Original Drake 784-139 output transformer

• Original choke

• Original Mullard mustard capacitors dated to the fourth quarter of 1974

• Handwired turret-board construction

• Original factory inspection sticker dated 21st April 1975

Professionally Serviced

Freshly serviced on 21st September 2026 by Dave Wittering of Prestige Amp Servicing, former Marshall senior service engineer.

The following work was carried out:

• HT fuse replaced – T500mA

• New matched pair of OEM Marshall EL34B output valves fitted

• Bias circuit smoothing capacitors replaced

• Screen resistors replaced with correct specification components

• All six potentiometers replaced

• Dedicated chassis earth fitted for electrical safety

• Professional inspection and operational testing

The amplifier is in excellent working order, fully serviced and ready to use.

Valves

Preamp Valves: Marshall-branded ECC83 / 12AX7

Power Valves: New matched pair of OEM Marshall EL34B

Cosmetic Condition

The amplifier is in very good cosmetic condition for its age, retaining its original:

• Headshell

• Tolex covering

• Marshall logo

• Handle

• Feet

There are minor age-related marks consistent with a vintage amplifier, but overall this is a particularly well-preserved example that has retained its original appearance.

Worldwide Shipping Available

All of our amplifier heads are shipped in custom-made Overdrive Guitars boxes, with additional internal protection to ensure they arrive safely.

We are proud to be an Authorised Marshall Retailer, offering new Marshall equipment alongside our carefully selected collection of vintage and pre-owned amplifiers.

Our dedicated West London showroom is available by appointment, where customers are welcome to view, test and experience our amplifiers in person.