RPM Adjustment Bulb Replacement
Direct drop-in LED replacements for the incandescent bulbs in the RPM adjustment panel of DC-motor BeoGram 4002 and 4004. The boards solder directly to the original solder points.
BeoGram 400X · Open source part
LED RPM adjustment lights
The bulbs behind the 33 and 45 rpm scales on the BeoGram 4002 and 4004 panel have usually burnt out after more than 40 years. I replace them with a warm white LED PCB of my own design.
The 33 and 45 rpm scales on the BeoGram 4002 and 4004 operating panel are each lit by a small incandescent bulb, rated 24 V and 40 mA, sitting behind the potentiometer housing. The speed relay 1RL1 switches between them, so the lit scale shows the selected speed. After more than 40 years most of these bulbs have burnt out, and the panel no longer shows which speed is set.
I replace them with an LED PCB I designed for the job. A warm white LED gives a colour close to the original bulb, and the PCB solders directly to the original lamp points, so fitting it needs no changes to the wiring. A 3D printed housing locks in behind the potentiometer housing, where the original bulb sat.
The PCB and housing are my own design, listed under parts, with the design files on GitHub.
Parts
More work
More on the BeoGram 400X
BeoGram 400X overview
Relay replacement
The original relays in the BeoGram 4000 series wear out with age. I replace them with my own relay PCBs, built around modern Omron relays.
LED tracking sensor
The BeoGram 4002 tracks the groove with an optical sensor lit by an incandescent bulb that dims with age. I replace it with a calibrated LED on a small PCB.
Speed testing with SpinDex
Every BeoGram 400X I restore is speed tested with SpinDex, an open source RPM logger I designed for the BeoGram 4000 series.
RIAA preamp
A new RIAA preamp for the BeoGram 4002, built around the OPA2134 in the same form factor as the original board. The second SMD prototype is built and tested.
Sledge motor
The original sledge motors in the BeoGram 4000 series can get noisy and unstable, and their bearings can't be serviced. I replace them with a modern Portescap motor, with a Maxon motor as the alternative.
Pickup mount
The plastic tab in the BeoGram 4000 pickup mount can break with wear and age. I replace the mount with my own nylon part and flexible PCB.
Restoring the keypad and chassis on a BeoGram 4002
Decades of use wear through the varnish and black paint on the BeoGram 4002 keypad. I strip it, have it professionally painted and refit it to the chassis.
Want one for your BeoGram 400X?
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