DP Specials Karaoke Set Module

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.

Imatronic SX3000 Slide Dissolve Unit

Saw this unit lying around at a thriftstore (€5) thinking it had something to do with audio because it had tape written all over it. Then I googled and found something about the Hammond XC3000? Like is it some sort of rotary speaker controller? I got excited and bought it right away to find out later it’s nothing but a so called slide dissolver.

I think the big idea is that back in the day where slide projectors were still a thing, you’d set up 2 of them and used a slide dissolver to switch between the two and make some sort of interesting audiovisual spectacle.

I don’t own any slide projectors and audio intrigues me more than video, so I might reuse the fader controller as some sort of synthesizer ribbon controller.

Anyway, I opened the thing up. It was full of CMOS logic ICs so that was a nice sight. Less nice were the amount of repairs that were done to it. I guess it wasn’t very reliable but important enough for the previous owners to replace chips capacitors and resistors all over the board. Anyway here some shots:

Excuse me for the mess. So we have a hand control input for the fader controller on top there, and a tape input I assume for… audio? The rest of the LEDs and buttons are a mystery to me. The device also uses 50 shades of DIN connectors so there’s no DC input or other simple way to turn it on.

Opening up the fader controller, we see a slide potentiometer with two end switches. I assume they allow you to go to the next slide. There’s also this blue non latching switch labeled “FLASH”. Not a single clue what that’s supposed to do but induce seizures on those watching the show.

Look at that! Quite beautiful if you ask me. Nowadays we’d use a single microcontroller to handle all of this, but back then? Digitial CMOS everywhere.

As I have no clue how this device works, can’t find any schematics or am bored enough to trace the whole machine, I’ll just leave you with a load of closeups of the board!