Dutch thriftstores have these now and then for nearly no money because they lack the microphones, power supply etc. etc. but they house one very particular part which I’m interested in.
But what is it? Just a main module for basic karaoke parties. Plug in 2 microphones, set the tone (variable low pass filter) and individual mic volume. And as a bonus you can add in an echo/delay at a fixed delay time and feedback level. The module is meant to sit between a game console or DVD player (just anything that can play shitty karaoke songs) and then have its audio fed to a tv or whatever as it also has a video in pass-through.
Teardown
Removing the top (by removing 4 philips head screws from the bottom) reveals all the through-hole parts including a particular DIP IC. This is a CD2399GP which is similar to a PT2399 but from another manufacturer. As all the PT2399s I bought from China gave me various issues, desoldering these becomes very worthwhile.
Note how there has been a patch at D1 in the top right corner. Has someone been in here before or did someone had to make sure it passed quality control?
Not a lot else to see here, some filtering caps and the pots. More interesting is the little cutout in the PCB and the shape of what might’ve been a battery holder in the bottom of the module. These enclosures are probably used for many different devices.
On the bottom a lot of SMD of which mostly opamps do the necessary audio trickery. Really not anything worthy to look into further.
The backside reveals how the audio and video pass-through works. Unit runs on 9V center positive adapters. This might raise questions as to why there is a 78L09 on board.
Trevor's Repair Café 