Tandberg TT1200 DVB MPEG-2 Decoder Teardown

Teardown of some old and discarded DVB MPEG-2 Decoders that have been used in a large buildings distributed TV network. Despite that units look the same on the outside, they turned out to be very different hardware revisions on the inside.

The front of the Tandberg unit only has a display and 4 input keys. At the backside there is coaxial signal input, card reader, RS232, audio and video outputs.

The old unit is built up with a mainboard that has a connector for a backplane, on which 4 cards are mounted. The newer Tandberg has a main CPU, which is a Xilinx XC4013 FPGA with a 27 MHz crystal sitting next to it. The C-CUBE AViA-DMX provide one end of a highly integrated MPEG-2 transport chipset. The STi3520ACV is a MPEG Audio / MPEG-2 Video Integrated Decoder. All the following cards are just made into one board on the newer units.

The power supply is pretty standard on the input in the right side of the picture. Bridge rectifier with common mode noise filter, capacitors and a fuse. The primary side of the transformers are driven by single transistors, which sit on a live heat sink! The output seems to be at-least two different voltages, red/black is the high power main source and the other 3 are likely 2 different lower voltages for different CPUs.

The input signal card has its own dedicated 7805, 5V regulator with a large heat sink. The shielded analog-to-digital ADC conversion goes into a unknown Philips IC with a 16 MHz and 61 MHz crystal sitting next to it. The VLSI VY27065 is a Satellite DVB IC of unknown function and the VLSI VES5453 Satellite FEC COMATLAS is a Forward Error Correction Decoder.

Besides the cardreader plastic enclosure, the large IC really stealing all the attention here is the DiviCom DMX-2000+ MPEG-2 TRANSPORT DEMUX IC. There is also a Xilinx XC3142 FPGA with 27 MHz crystal and a good oldschool Motorola MC68ECO20 microcontroller which most likely runs the very old cardreader software. The amount of different MPEG-2 decoders in this products makes me think that a lot of jobs are done twice or three times, in different places, instead of treating all data in a central CPU.

The output card has two Xilinx XC3142 FPGAs near the backplane connector. The STi3500ACV is only a video decoder IC, unlike the 3520 we saw above that is both video/audio. The Texas Instruments TMS320AV110 MPEG audio decoder supports all ISO-MPEG audio decompression algorithm. The audio output is served by a Philips TDA1305T, where you can almost always recognize a audio IC by the TDA start, its a stereo 1fs data input up-sampling filter with bitstream continuous dual DAC (BCC-DAC2)

The more modern Digiality SMATV 212S is build around a single IC solution from ST.

The STi5517 integrate more core STB functions into a single device than ever before, offering STB manufacturers the opportunity to build cost-effective solutions powered by devices from the leading supplier of MPEG-2 ICs.

ST Microelectronics

Mads Barnkob

Electrician, programmer, experimenter and amateur scientist with experience in industry automation, programming and all kinds of high voltage generating electronics. Administrator of www.kaizerpowerelectronics.dk and the high voltage community forum www.highvoltageforum.net

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