This will be a simple, non-thorough teardown of a DENVER DAB-43C PLUS DAB/digital radio (with FM). For my own interest, I wanted to see how much design work is put in the product by the final manufacturer (in this case, DENVER). I know of some DAB modules and integrated circuits, like the Atmel DAB-On-Chip ATR2740, and are always interested to see what other solutions are used in the most lowest cost consumer products. My intention is to, some time, add DAB functionality to an old FM/AM radio.
In total there are 4 screws to remove, one in each corner on the back of the radio. Start prying from the bottom on the front cover because the cover is hooked to two fastener clips on the top.
If you don’t have a nylon tool for opening cases and are afraid to scratch your product, just pry on the underside of the radio so any possible scratches won’t be visible when you’re done.
The inside reveals a very modular design, as expected. The main PCB has a standard 0.1″ header pin footprint for mounting a ready-made DAB module from Quantek, model Q7+. As stated by the manufacturer, the module is delivered pre-programmed to it’s costumers wish, so no programming for the LCD controller or switchboard is necessary. That must make it a breeze to implement.
External PCBs include LCD screen module (looks to be the very standard one popular in DIY builds, so should be easy to change if you want a different colored one)
Lots of glued down components means the manufacturer has put some effort into making the product sturdy, but it also makes for some messy visuals when inspecting if it’s done in a hurry, like here. There’s super glue all over everything, but I guess it doesn’t really matter.
Since all components are trough-hole, and not not all solder joints are uniform in size, it’s fair to expect this product is hand soldered and assembled.
The designer has conveniently labeled all inputs and outputs that goes to the line in/out and power input.
|R_IN||Line in Right channel|
|L_IN||Line in Left channel|
|R_OUT||Headphones line out Right|
|L_OUT||Headphones line out Left|
A couple of very easy to spot design errors caught my eye. The first one being the LCD ribbon cable connector is rotated 180 degrees compared to the LCD position. This causes the cable to shorten a bit, and the tension from the left most wire actually pulls the connector outwards.
The second error looks a bit funny. It’s a big electrolytic decoupling capacitor on the supply voltage pin of the TDA2822M, the audio amplifier chip for the headphones. I can image that cap must be a real pain to solder, so I hope that poor technician built himself a simple rig of some sort for the job. Also there’s a single wire from the ground lead on the cap to a solder pad on the DAB module where it’s supposed to sit a screw. Who knows if the screw was missing first, or if they removed the screw so they could attach the wire? It could be fun to have a look at the audio output with and without the cap. maybe later. My guess is that a less cheap AC/DC adapter would also do the trick.
On request, I’ll add the key mapping with schematic and inputs for my radio. I had some trouble tracing the input lines, also as requested, as it only seemed to go straight trough the headphone amplifier chip and out “line out”.