Denver DAB-43C PLUS radio teardown

Denver DAB-43C PLUS radio teardown

DENVER DAB-43C PLUS front view

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.

DENVER DAB-43C PLUS back screws

4 screws must be removed from the back

DENVER DAB-43C PLUS opening

Pry the cover open from the bottom, it's hinged on the top

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.

DENVER DAB-43C PLUS main board

Main circuit board

DENVER DAB-43C PLUS overview inside

Overview of the insides

DENVER DAB-43C PLUS module

Quantek Q7+ DAB/Dab+/FM module














All additional circuitry on the main board are power conditioning, audio amplifiers for headphones (TDA2822M) and speaker (TEA2025B) and connectors for connection to the outside world.

DENVER DAB-43C PLUS block diagram

Roughly drawn block diagram of the product

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)

DENVER DAB-43C PLUS lcd

LCD module

DENVER DAB-43C PLUS diode

Unpopulated diode?

DENVER DAB-43C PLUS lines in out

Line out connector labeling














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.

GND Ground
DAB_L Antenna
DAB_R Antenna
R_IN Line in Right channel
L_IN Line in Left channel
P_SW Power switch
R_OUT Headphones line out Right
L_OUT Headphones line out Left
GND Ground
VCC +6V



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.

DENVER DAB-43C PLUS bad connector

LCD connector

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.

DENVER DAB-43C PLUS capacitor

Big capacitor bodged on by hand

UPDATE
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”.
DENVER DAB-43C PLUS keys

DENVER DAB-43C PLUS Keypad drawing

Keypad drawing


DENVER DAB-43C PLUS keypad schematic

Keypad schematic

This article has 14 comments

  1. New blog post: DAB radio teardown. Lots of pictures and a few funny design errors http://t.co/BGqEFLqi

  2. Wow, looks like a real mess inside, at least the caps are anyways, they could’ve used some hot glue or something. How much are those units?

  3. Hi Henrik,

    first of all, nice Pics!
    As I lately had to open my DAB Radio (HDigit Fii-Posh) (it was broken) I also found the Q7+ Module. Found your page via google and also Quantek’s main page with the rather poor dokumentation. However the little note of the Aux-Input and also the Ipod thing got my focus. I dont really think that they Programm each Module seperately, hence it should be possible to connect an Ipod to the module. Therefore, for a first test it would be glad if you could send me a more precise schematic of the Line in path to the module and also the Keypad schematic with the row and col info, so that I can try to rebuild your keypad on my radio, to see if the Line In works on my radio.

    Thanks and Greetings from Switzerland
    Roman

    • Henrik Sandaker Palm
      Tuesday 7 February 2012, 8:46 am

      Hi Roman,
      Glad to see you have taken interest in my post. About programming the module separately, I guess some functionality will always be be on the module, like hardware lines (in/out), but roughly 50 pins to support all types of LCDs, keypads and iPod functionality i think is optimistic.

      Sure, I will update the post soon with more info on the keypad and audio lines. I’ll send you an email. It’s sad I don’t know Swiss, as your blog post seems very interesting and google translate is a bi*** to read…

      • Hi Henrik,

        well I thought that all the electrical engineers are optimists ;-) ? Well to be honest, I just like to try it ;-). Just wondering how they got all the stuff out of the iPod, as I made an FM-Tranmitter (more Power that the cheap ones you can buy ;-) and further supporting RDS) for the iPod. And maybe I I get some more info about the iPod Accessory Protocol that the other folks.
        Therefore looking forward to hearing from you!

        Well I know I really have to switch my blog to english but I guess you know the problem with the time ;-).

        Greetings
        Roman

        • Henrik Sandaker Palm
          Tuesday 7 February 2012, 3:30 pm

          That’s a real project you’ve got ahead of you at least! The post is now updated with pictures. I will take a closer look at the line-in traces some time soon.

          I guess you will be notified by mail now.

  4. Hi.

    It’s interesting to find another fellow countryman that tears this radio apart. I have actually rebuilt mine for use in the car but my main problem is a weak and very varying signal in most areas.

    I have adapted an active DAB antenna ment for Pure DAB and have also tried an amplified FM car antenna, both with less than acceptable resilts. Now I realise that there are actually 2 connectors for 2 antennas?

    Do you have any idea how I could achieve the best reception in a car? I seems like there’s missing ground regardless of how I setup things. If I hold around the antenna wire, the signal is Ok, but not otherwise..

    Any tips are welcome.

    • Henrik Sandaker Palm
      Monday 1 October 2012, 1:57 pm

      I don’t really know radios, but I also thought DAB antennas were supposed to be active type, at least that’s what I’ve seen in cars. But you had good reception indoors while the radio is stationary? Where do you see another antenna connector?

      I am sure you’re aware of the actual DAB coverage in your area

      • Yeah, the reception inside was ok. Also even with just a simple copper wire as antenna but as soon as I place the radio inside the car, the reception varies from full to nothing all the time. That is unless I hold around the coax cable. I live in hadeland so the coverage is quite good.

        Actually, regarding the 2 antenna connectors. I assumed that looking at your picture with DAB L / DAB R info. But that unshielded flat cable is obviously not tranferring radio signals so there is in fact only one input which is used for the telescope antenna by default.

        I’m not sure how to adapt this one for car use without dramatic modifivations..

  5. Hi, how would i go if i wanted to upgrade the speaker in this one?
    Is there any way to increase the voltage to the amplifier chip? as I understand it could use some more voltage, also i was thinking about replacing the speaker itself to a more powerful one.

    I may also give it a new AC/DC adapter, maybe a 12v one? or 9V? what do you think? and how should i go if i want to connect all this together? :)

    Thanks i lot, hope it isn’t to much to ask for, and i would be extremely happy for some help! :)

    Best regards.
    Jøran

    • Henrik Sandaker Palm
      Tuesday 5 March 2013, 11:34 am

      As you may have noticed, the AC adapter is only 6v so my guess too is that the TEA2025B could do with some higher voltage, but be sure to read the datasheet first (TEA2025B has a absolute maximum 15v supply voltage) . Also you need to examine the circuit and/or isolate so you don’t exceed any other maximum voltage ratings. I don’t know if the speaker should be changed if you up the power a bit, best way is just to try it out, it should be a plug-and-play thing.

      What you also could do is simply adding a better amplifier and mount it freely inside the case, that would probably simplify a lot of things. Most likely you’ll need a 12v supply, so you can use a 12v supply for the new amplifier and DC-DC step down the voltage to 6v for the radio circuitry.

  6. nothing more on the pinout of the Quantek Q7+ DAB/FM module?

    it seems that it has an SPDIF output, but unfortunally i dont have the equipment to do some trial en error testing :(

    My Q7+ is build in a AEG DAB 4130 radio, seems to be identical to your DENVER model. but with a slight change in the PCB layouts.

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