tecsun: Tecsun PL-330 - Internal circuit observations

This Tecsun PL-330 model uses two main PCB's assembled in piggyback mode:

• The Digital PCB - Marked as PL330KZ-V4.
  • ​Public pictures shows codes like 20-18, 20-19, or 20-29 (2020 weeks 18, 19, 29 dates?).
  • The heart of the radio receiver lies on a Silicon labs Si4735-D60 chip (IC2 marked as 3560). 
  • The control and management is handled by a unknown, customized obfuscated reference, "952DZ03 0C07AA" MCU chip (IC1)
  • The MCU uses a BL24C256A 256kbit 32KByte EEPROM (IC2).  
  • One 0.22F 5.5V super-capacitor handles the backup power supply whille changing the removable battery.
  • There is a 4-pin connector at the LCD display side (KP1) whose function is not documented.

• The Analog PCB - Marked as PL330 DT&GF - V4 2020.3.6.
  • Public pictures shows codes like 20-18 or 20-29 (2020 weeks 18, 29 dates?).
  • The Audio amplification is designed around a CD1622CB dual channel power amplifier (IC1), driving the earphones in stereo mode thru a RC series limiters/filters, and the built-in speaker is driven in Mono mode in BTL (bridge) mode. Interestingly, the PCB silkscreen is marked as CXA1622.
  • The Power Supply section takes the 3.7VDC from the BL-5C removable battery or from the 5VDC USB port, to supply regulated voltage of 2.8V, a SW voltage for the SW RF Front-End, a +V unregulated voltage, and a battery charger circuit.
  • The RF Front-End uses a BAV99 (D1) at the telescopic antenna/antenna socket to protect the RF circuits. The FM signal is passively passed  to the Digital PCB to the DSP chip using a dedicated coaxial cable with RF connectors, bypassing the piggyback connector. The AM SW signals are passed thru the LC network to a two stage front-end (1Q1 and 1Q2) and then passed to the DSP in the Digital PCB using the piggyback connector (MW/SW pin). The AM MW signal is passively passed to the DSP chip (using the same MW/SW pin).

To thank the Author because you find the post helpful or well done.