Smps - Akai DVP6333KDM Service Manual

4.2.1 Front Panel Interface
6 Pin, Data Connector Pin Assignments
PIN NAME
1 REM
DATA
2
3 CLK
4 STB
5 GND
6 VCC
6 Pin, Power Connector Pin Assignments
PIN NAME
1 VFD 1
2 VFD 2
3 -21V
4 STBY
5
GND
6 +5V
There are 3 different devices operated by the PIC508 and Pt6312 (Optional):
* Vacuum Fluorescent Display (VFD)
* Push-buttons
* LEDs
There is an option for a tray lamp and a joystick which is not currently assembled. The VFD display is custom made,
implemented in a 6 grids by 16 segment matrix.
The VFD needs special voltage supply for operation:
* Vkk which is -21V needed to drive the segments and grids of the VFD.
* Vf1, Vf2 which powers the exectron cloud filament (cathode) with a differential voltage of 3.5V. This is a floating
voltage difference generated by the power supply, and is biased to -21V in the ront panel board by a Zener circuit
from the -21V (Vkk) supply. Moving the bias towards a more positive number will reduce the segment brightness.
Vf1 & Vf2 provide a DC supply to the cathode. To overcome the voltage difference between one end and the other
of the cathode, it is geometrically titled so that the segments observe the same potential and have all the same
brightness. Other way to overcome the problem is to employ an AC supply to power the Vf1 and Vf2.

4.3 SMPS

The mains power(220VAC) fed from N1 is filtered through C1, L1, C2 and L2 then rectified by D1, D2, D3 and D4
and generates an output at 300VDC. This 300VDC fed to T1 (pin2, pin4) which connects to 5L0380R(pin2), then
5L0380R will automatically generate a 50KHz square waveform, this 50KHz square waveform controls the ON/OFF
between 5L0380R pin2 and the ground. In normal condition, T1 primary (between pin2 and pin4) will create a
50KHz square waveform which is controlled by 5L0380R, this signal then fed to T1 and generates 2 different
potential voltages of 12V and 5V between pin17, pin14 and pin16, pin14 respectively. The 12VDC and 5VDC then
rectified by D7, D8, D9 and then filtered by L3, L4, L5, C9, C10 and C11. The feedback voltage is controlled by Ic3
TL431 and IC2 PC817. When the output voltage is higher than 5V, the voltage at TL431(2.5V) is compared with
R10 and send out a signal to 5L0380R, the output square waveform then will change to adjust the output voltage,
this acts as a voltage stabilizer.
I/O DESCRIPTION
Front Panel Data input
I
IR sensor interrupt
I
Front Panel chip select
O
O Front Panel clock
Front Panel Data output
O
FROM DESCRIPTION
Segment and grid Voltage of the VFD
SMPS
Provide a DC supply to the cathode. To vercome
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the voltage difference between one and the other
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of the cathode.
SMPS
SMPS
Supplies IR and Front IC
SMPS
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