Please see Larry R. Lockard's, N7FM, excellent Step by Step Procedure to open the Astron Power Supply Meters, remove the Neon Bulbs, and install the LEDs.

Since my Astron VM-70 Power Supply has a variable Output Voltage, I use a simple Voltage Regulator, fed by the Power Transformer's Secondary, to provide a fixed 12 Vdc to the installed Meter LEDs. See the Details below.

Schematic Diagram:

The Value of the Resistors can be changed for the desired brightness.

150% scale of Printed Circuit Board, PCB:

Sketch of Parts Placement:

1N4003 Diodes and 470μF Capacitor are bottom Side of PCB.

Photo of Diodes and Capacitor Placement, prior to PCB Installation:

Photo of completed PCB Installation:

Second View of completed PCB Installation:

View of Astron VM-70, with Meters lit by LEDs: