Keywords: radio tap
(1) Remove several screws of the fixed casing, open the casing, pull the flat connection cable between the front and rear circuit boards from the outlet, remove the motherboard, welde the digital circuit board (before being installed before the casing The outer shield on the ministry, remove the plurality of screws of the fixed plate, remove the digital board.
(2) On the digital circuit board, the charging resistor R237 (20) is removed, and the original charging circuit is broken; on the main board, cut off the charged socket negative electrode print line, and connect it directly to the battery negative side. The additional two ends of the socket are again connected together, remove the resistors R169 (1K) on the socket to avoid the air consumption of 3.6 mA.
(3) On the digital board, remove the second, third, fourth tuning LED, only one indicating LED, while removing two LEDs of the lighting keyboard, only retaining the LCD LED LED, so it on the keyboard The remaining light illumination is sufficient, and the photoresist is removed, and the B-pole circuit of the QLO5 of the control backlight LED is disconnected from the upper end of the C203. It is used to save the backlight to save the battery and increase manual backlight control.
(4) Remove the SSB switch, the intermediate frequency transformer T11, the integrated circuit U8, the potentiometers VRI, and Q31, C43, DL5, completely remove the SSB receiving circuit, and leave a space on the motherboard.
(5 (On the motherboard, a series of components on the audio channel is removed, so that the output of U2 is directly U3, remove CLO3, CLO4, CLO7, QL3, QL6, CLL4, enlarged and excessive prefix in the original audio channel. Cumshot, CLO5, CLO8 (47N) replaced with 10On (expand low frequency response), replace R23, R24 (4K7) to 1K (improved signal level), then connect C1O5, C1O8 left end with wire, C27 (1U Replace to 1ou; CLL5 (47n) replacement to 1U; remove Q30, Q32, remove static noise, demolition Q24, Q26, and cancel the lowest level volume control.
(6) Remove the R78, increase an NPN triode and a 22K resistor, and the circuit is changed to see the following figure, the purpose of this move is to power 3mA of MW band.
(7) Remove C1O3, R1O7, C1O6, R117 components, and use the knife cut switch Public end printed line) Two switches in parallel) One end is connected to the backlight control line drawn from the digital board, and the other end pick U5 output Terminal, manual backlight control) it is still valid in shutdown.
(8) The most critical improvement is shown in the power switch section, as shown below. ICI is a negative pressure conversion integrated circuit ICL7660 that provides sufficient negative pressure for two PMOS power tubes Q1, Q2, and controls the switch of the power supply. The function of Q3 is the power switch for IC1, directly received by the radio number board. ON / OFF Level Control. When this level is low, Q3 is turned on, IC1 obtains 3.6V operating voltage, generating -3.6V voltage plus on Q1, Q2 gate, so that the two tubes are turned on, the radio gets the power supply to start operation; When the ON / OFF signal becomes high, the circuit stops working, the radio is closed.
The circuit's printed plate is shown below, and its size is just a region of the original T11 near the motherboard. The reader can use a 1 mm copper plate to make a printed plate, and must use double panels, front mounting devices and wiring. The back is grounded as a shield plate, and the patch element is tightened. The ICL7660 in the circuit is also a chip device, Q1, Q2 can select 1A or more device) Model is not limited. The pipe used by the author is part of the disassemble from the computer motherboard. After the circuit is installed, several outer terminals are drawn from the wire, and then attach the back of the circuit board to the insulating tape, and stick it on the radio motherboard with a non-glue, then connect the wire.
The power supply unit has an oscillating signal with a switched negative voltage conversion chip, and if the entire unit can be mounted in the shielding box to prevent it from interfering with the host, but the author does not install the shield box. There is no obvious interference, only a slight call at the empty frequency of the FM band, there is no impact after the signal.
Remove the Q34, Q36 of the original motherboard, and then connect the lead wire of the self-made circuit from the front of the printed board to the respective end, see each end of Figure 3; the quadrant power consumption of the circuit is only 270μA.
(9) The final step is to completely restore the assembly of the original machine, connect the flat cable, etc., reinstall the second layer shield of the digital printed board, such as a better speaker unit, can replace the original unit, to this machine Caled a paragraph.
After the above-mentioned machine, the performance of DE1102 has a small change, and the treble bass has certain expansion, distortion is small;, the volume is also sufficient, especially the power consumption indicator, the measurement of the shutdown is 1ooμA, FM34mA, MW36MA, SW36MA, the battery use time is prolonged.
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