Circuit Operations - Panasonic KX-F1200 Service Manual And Technical Manual

KX-F1200 t
3-2. THERMAL HEAD
1) Function
This unit utilizes state of the art ther,lal primer technology.
The ink film is chemically processed. When the thermal head contacts this ink lilm it emits heat momentarily, ink film is
melted and transfered to the paper. If this point is continued, litters and/or diagrams appear, and the original document is re-
produced.
COMPOSITION OF THE RECEIVE RECORD SECTION (THERMAL RECORDING FORMAT)
Thermal Head
\ , jlnkFilm
_ .______ Paper
Platen Roller
2) Circuit Operation
There are 27 driver ICs aligned horizontally on the thermal head and each one of these ICs can drive 64 heat emitting regis-
ters. This means that one line is at a density of 64X27=1728 dots=(8 dots/mm).
White/Black (white=0, black=l) data in one line increments is synchronized at IC417 pin 35 (NEWTHCLK) and sent from
IC417 pin 34 (NEWTHDAT) to the shift register of the iCs. The shift registers of the 27 ICs are connected in series, and upon
shift of 1728 dot increment, all the shift register become filled with data, and a latch pulse is emitted to each IC from IC404
pin 34 (THLAT).
With this latch pulse, all the contents of shift registers are latched to the latch registers. Thereafter, through the addition of
strobe from the IC404 pins (29, 30, 31,32) only dot of location of black (=1) among latched data activates driver, and current
passes to heat emitting body to cause heat emission.
Here the strobe of four lines STB1 to STB4 impresses at intervals of 9.216 msec, as required for one-line printout, for each
1/4th of 27 IC unit (6 unit or 7 unit) upon each time interval divided into four equal increments.
The sequence is as shown below. [Moreover, in the case of strobe width, the resistance value of the thermistor inside the
thermal head is constantly detected by IC404 pin 2, and vales from the ROM (IC402) table corresponding to temperatures
eliminate temperature changes of density through setting by CPU (IC401).]
When the thermal head is not used, the IC401 (6, TH-POWER) becomes low level, Q407 becomes OFF, RL201 breaks, and
the +24 V power supply for the thermal head driver is not impressed to protect the IC.
- 104-