BeoGram 400X · Open source part
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.
I'm designing a new RIAA preamp for the BeoGram 4002, in the same form factor as the original board. The second SMD prototype is built, tested and working.
It's a dual-stage active RIAA design based on the classic LM833 topology, built with the OPA2134, aiming for low noise and stable performance without unnecessary complexity.
Still to do:
The project is open source on GitHub.
Replacement RIAA preamp for the BeoGram 4002, built on the same form factor as the original board. A dual-stage active design based on the LM833 topology, implemented with the OPA2134 for low noise. Fully SMD. Still in development: the second prototype is tested and working, and measurements are in progress.
More work
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.
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.
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.
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.
Tell me about your BeoGram 400X and I'll get back to you.