415
Item nr.


Gerard Rytmus Bluetooth speaker

Retro style modern device


Data for Gerard Rytmus
ProductionThe Netherlands, 2015.
Price was €32.
BandsFM.
Semi-
conductors
PCB: HF-521-V1.1 (2014.11.25).
CabinetBakelite. Weight 3.4kg.
Power5V USB or battery.

The Design

Is it a repaired Tesla radio, a refurbished bluetooth speaker, or a construction project? I chose to list this item under the home projects of GRC.

In 2014 I got an old, non-working Tesla Rytmus in Czechia, and in 2015 I got additionally some bluetooth speakers from Czechia. I could repair the Tesla, but I prefer to rework the stuff into something that you can really use. The bluetooth device is quite versatile: it has a speaker and bluetooth receiver, but also an FM radio, and MP3 player built in. All operated by 4 pushbuttons. So let us open the bluetooth device and look inside.

It has a very small speaker (3cm, but remarkably with quite good bass response), a small PCB with some chips, a small rechargeable battery. The user chooses the functionality with four buttons, operating contacts on the PCB. The PCB is 31x42mm and has two USB interfaces and a microSD socket for a card with the music files.


Obtained9/2015 from home construction.
Condition8.
Sound samplePLAY SOUND   You hear Profofiev's Pushkin Waltz from 1949, like you never heard it before from an AM only radio. The original, extremely small speaker is almost better than the recased one with 15cm broadband speaker. The 1948 Tesla speaker gives less trebles and some more basses.

This Object

The PCB from the bluetooth speaker goes into the radio cabinet. I mounted the tiny board on a piece of plywood with screw connectors. All old electronic parts from the Tesla radio were removed, except for the tuning capacitor. I left the tuning control (including knob, dial drive chord, and pointer) in place, so with this bluetooth speaker you can also move a dial pointer along a retro style dial. In this picture the set has a modern car speaker, but I found the sound better with the original 1948 speaker.

Some measures are needed to operate the device from the outside. I soldered four leads to the push contacts and connected these to punaises near the volume control of the radio. This gives a monoknop style of operation, where all four buttons of the bluetooth device can be activated by the volume control. These controls are: (1, white wire) Button pushed IN, to the LEFT, long for power on and off. (2, blue) Button in, turn right long for mode switch, short for station search in FM. (3, yellow) Pull button OUT and turn left SHORT for previous station of music file, LONG for volume down. (4, green) Button out, turn right SHORT for next track or station, long for volume up.

The original PCB is accessible and visible through the back. Connect the micro USB as an antenna or for charging (complete when red light goes out). Place microSD with music files, device starts in player mode then.

For home use, I found the lowest volume level too loud already, so on January 20, 2019, I soldered en 40 Omh resistor in the speaker lead.

The unit is charged with a standard USB plug charger. After charging (up to 120 minutes) the device should play three hours. Shortly after a discussion I heard about the safety of cheap Chinese chargers, my charger fell apart while I unplugged it. With the hot leads open, this could have been a severe shock for me!


Part of Gerard's Radio Corner.
Generated by SiteBuilder on 20/1/2019 by Gerard (g.tel@uu.nl)