Speed testing with SpinDex
Every BeoGram 400X I restore is speed tested with SpinDex before it goes back to its owner. SpinDex is an RPM logger I designed and built for the BeoGram 4000 series. It sits on the platter, where an IR sensor measures the rotation and streams the RPM over Bluetooth to a web app.
A test runs for hours unattended, so drift and warm up problems show up before the unit ships. The app graphs the current, average and maximum RPM with the deviation from 33⅓ or 45 rpm, and every session can be exported to CSV.
SpinDex is open source under the Apache 2.0 license. The firmware, the web app, the 3D printable enclosure and the carrier board are all on GitHub, and the web app runs in Chrome or Edge at spindex.leicht.io with nothing to install.
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.
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.
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.
Have a BeoGram 400X that needs this?
Tell me about your BeoGram 400X and what's wrong with it, and I'll get back to you.