Dating vox ac50 demetri martin dating
The "Big Box" cabinet also allowed the chassis to be mounted to a "slider board" for ease in service.
To service the chassis, one only needed to remove six back screws, remove the rear panel and slide the chassis out of the cabinet like a drawer.
North Coast Music offers a replacement AC-50 slider board to correct this problem.
The AC 50 Mk III and Mk IV amp heads would typically have black Vox grill and use the later, "three field" Vox Amplifier serial plate, as shown at right.
This weakening has caused many of these slider boards to snap under the weight of the amp chassis.
Should this occur, the chassis and control panel drops inside the cabinet.
This circuit, detailed on JMI schematic OS/75, would resemble the reverb installation on the Vox AC-30SRT head.
Two controls would be mounted in a hole in the back panel and a reverb pan would be suspended from the bottom of the slider board.
Installing EL-34 tubes that are not rated to operate at the 460 plate voltage of an AC-50 can create premature failures.This serial plate was installed on JMI amps produced from 1965 to 1967.It is a fairly safe bet that an AC-50 amp head with this "three field" serial plate is one of the diode rectified AC-50 models.It can be a challenge to install modern EL-34 output tubes in the AC-50.Many modern EL-34 tubes are too tall to fit in the clearance between the chassis and top of the cabinet.