Thursday, September 19, 2013

Lidl "pound shop" FM radio with Alarm Clock

Back in the year 2004 I had a lot of fun with modifying a cheap FM scanning radio to a direct conversion 40m CW receiver.
http://www.kufr.cz/~ok1iak/HAM/PoundShopRadio/index.php3

I was inspired by Hans Summers:
http://www.hanssummers.com/poundshop.html

Hans documented yet another reincarnation of the scanning FM radio, this time with a LCD display.
http://www.hanssummers.com/superdrg.html

Once I stumbled over a FM scanning radio with alarm clock, I hoped I would be able to do a similar conversion and I hoped the frequency counter would be possibly bendable to HF as well.

Front side, showing a FM frequency.

Rear side, closed.
 
Rear side, battery door removed.

Opened. There is a tiny crystal resonator on the rear side for alarm clock.

See the labels on the back of the PCB. It seems there is a general purpose MCU on the board, which may be reprogrammed. There are two tiny crystals on the board, likely one is the 32768Hz clock crystal, the other likely a reference clock for the frequency counter.



There seems to be a combined clock / frequency counter chip under the black blob. There seems to be another chip in a TTSOP10 package, likely the FM receiver chip. One transistor drives the crystal resonator, the other transistor (or maybe an IO) drives the earphones.

Unluckily there is some additional epoxy glue placed over the earphone amplifier and over the FM radio TTSOP10 package. This makes further reverse engineering impossible. The FM receiver chip is certainly not the common TDA7088T kind, which is usually packed in SSOP16.
 
 

That's the end of the story for me. Please let me know, if you can identify the new TTSOP10 FM chip.

73, Vojtech OK1IAK

No comments: