Ferrum - They brought me a JVC TV for repair.

AY-Track: I want russian prostitute,Merlin                    
By: Macros                                                    
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 В  начале  декабря принесли мне в ремонт
телевизор JVC. Неисправностей было две: в
блоке  кадровой развёрткиand in the power supply
nia.  The first one was eliminated quite easily -
It turns out that it’s also on “their” TVs
there is such a malfunction as de-
installation problems. It was good enough
I need to solder the legs of the microcircuit.            
 With the second malfunction there was little
more difficult. The TV sometimes turned itself off,
and in standby mode from the power supply
sometimes a sound was heard, but not at a high pitch
on, and low, peculiar clicks. And
now, one fine day, when I sit-
business and waited for the next time the box
turns off, I heard a bang, there was a smell
fumes and some smoke rose from the power supply
a big cloud of smoke. When examining the board I
discovered two exploded transistors and
burnt out breaking resistor (this is a mixture
fuse and resistor). Picking it up
multimeter, I found that in addition to the above-
the specified parts have failed micro-
diagram and a few small parts.         
 And now I want to tell you this: no-
when do not order radio components from a store
zine "Household Goods", which is near the market. If
If they get them to you, it will be at double the price,
this is the first thing. And secondly, I don’t like
their attitude towards clients has evolved, in
in particular, he ordered a microcircuit and
two transistors. They brought the microcircuit
and sold it for 100 rubles, although it was in Moscow
costs 50. For transistors, comrades pop
growth was scored. I had tocontact other
gee organizations. Other organizations
they were carrying transistors, but they could
sell for 60 rubles if needed. 
 I installed new parts, turned on the TV
zor - the protection worked, it turned out to be overloaded
leakage in secondary circuits. I had to change
116 volt zener diode. Then TV
earned it.  Only microcircuit parameters,
obviously a little different from the norm,
so I had to put the con-
470 pF 2.5 kV capacitor (from unit
line scan from "Record").        
                                                              
 Well, since we started talking about blocks
nutrition, then consider some simple
shady, with fewer details.           
                                                              
             
                        
                        
                        
                        
             
                        
                        
                        
                        
                        
                        
                        
                        
                        
                        
                        
                        
                        
                        
                        
                                                              
 (правда,  схема нарисована не полностью,
так  что  не удивляйтеась, если некоторых
деталей,  упоминающихся  в тексте, на ней
не  окажется. Не так то легко, оказывает-
ся, крыской схемы рисовать :-)) So, the power supply generates constant
stabilized voltages required
for operation of TV components, galvanic
ki not related to mains voltage.   
 The principle of all imported power supplies
TVs are based on conversion
rectified mains voltage at high
co-frequency pulse followed by
transformation into secondary stresses and
straightening.  Power supplies in which
there’s just a transformer with a bunch of windings
current and a huge number of rectifiers
leu stabilizers in secondary circuits
I haven't met.                             
The power supply circuit consists of:         
                                                              
-Surge filter  C633, LFbO0, C634,
LFbO1, C600, C635, C636;                 
-Rectifier with filter D600, C603;      
-Key modulator ICbO0, T601.       
                                                              
 The power supply is made on a microcircuit
STR-SB708. This is a PWM controller with built-in
with a new power key.The mains voltage, having passed the fuse-
tel F601, network switch S601 and room
CO2 suppression filter enters the system
mu demagnetization, performed on electric
ments THPbO0, DGC and rectifier D600. C
filter output constant voltage
+350V through winding 7-5 T601 is supplied to
collector of the key transistor, incoming
th into the composition ICbO0 (pin 1). Transmitter emitter
resistor (pin 2) through low resistance
R605, equal to 0.27 Ohm, is connected to the housing
catfish  Power supply to the microcircuit (pin 9) in the
the starting moment comes through the chain
R600, D601 from mains voltage. This
The power supply is low current and can provide
only the first switching on of the microcircuit.  B
further, after starting the converter
power comes from the stabilizer, its own
early on elements: Q601, D603, R603,
R634, C604, C605, D604 and connected to
winding 4-2 T601. Conclusions 7 and 8 ICbO0 are
are the inputs of two independent systems
monitoring the output voltage.        
 Pulse voltage proportional
output voltages, from the reverse winding
connections 1-2 T601 comes through diode D605
to the divider R604, R636 and then to pin 8
ICbO0. Capacitor C609 eliminates high-
frequency interference, thereby preventing
false alarms ICbO0.               
 When the output voltage changes, I
the amplitude of positive pulses increases
vyv.8 ICbO0.  This will lead to change
converter frequency so that the output
power supply voltages return to
to their nominal values.             
 In idle mode, the signal amplitude
catching 8 ICbO0 increases by 2-3 times
for. Protection is triggered inside the microcircuit.
The power supply goes into a mode in which
rum pulse duration on the collector
is about 1 μs, and the output voltage
The values are underestimated by approximately 10 times. Mode
protection prevents failure of electrical
cops of the power supply and the rest of the circuit
TV.  The second stabilization circuit is
the circulating voltage operates as follows:
at once: voltage proportional to input
ICbO2 goes to the LED from pin 2
ode of optocoupler ICbO1. At the same time, the brightness changes
bone of the LED glow and, consequently,
Therefore, the resistance of the phototransistor
optocoupler, one terminal of which is connected to
vyv.  7 ICbO0, and the other to the stabilizer
voltage +7 V. Changing the voltage by
vyv. 7 ICbO0 leads to a change in frequency
converter operation. Output voltage
values return to the nominal value.
 The power supply contains two circuits
current and voltage protection. Protection circuit
according to current it works as follows. B
emitter of the key transistor in the composition
ICbO0 measuring resistor is turned on
R605.  As the emitter current increases above
maximum permissible voltageon R605
will exceed the level of 0.7 V. Zener diode D601
will open and the Q601 stabilizer will turn off.
Supply voltage at pin. 9 ICbO0 will be
supplied from a low-current rectifier
D601, capable of providing only the first
triggering pulse of the converter. Pos-
then the voltage drops below 6.5 V
and the internal gene blocking will turn on
rarator.  Voltage across capacitor C604
will gradually increase at +9V
the lock will be removed, the key on the collector
a short im-
pulse duration 1 μs. After that
The supply voltage will decrease again and
The generator will be blocked again.
This power supply protection mode will be up to
until the cause is eliminated
overload.   Output voltages will be
practically absent (tens of times
less than the nominal value).           
 Voltage protection works as follows
way. In the event of a short circuit to the load,
On the power supply, the voltage disappears
input of the stabilizer from winding 1-3 T601.
Supply voltage of the ICbO0 microcircuit
will begin to flow through diode D601. Turn on
The protective “start-stop” mode is activated.    
 Operating mode of output voltage stabilization
The disguise consists of two schemes. The first scheme
ma works as follows: voltage
at the output of the power supply will reduce the voltage
on winding 2-1 T601, and at the input of the circuit
we are tracking ICbO1 (pin 8). This will lead to
increasing the duration of trigger pulses
and an increase in output voltages to no-
minimum values                       
 The second stabilization circuit works as follows:
as follows: supply voltage to
pin 1 of optocoupler ICbO1 comes with rectifier
body D608, C612. On the pin. 2 ICbO1 supplied
voltage from pin  2 ICbO2, proportional
the difference between the output voltage
+135 V and reference, i.e. voltage
errors.  Reference voltage source
goes to ICbO2. When the voltage decreases,
The voltage at the output of the power supply will decrease
error voltage. The resulting voltage
The light on the LED of the optocoupler ICbO1 increased
increases, the current increases, the resistance
phototransistor decreases.  Voltage
at the input of the tracking system (pin 7 ICbO0)
increases.  Duration of generated
pulses increases and the output voltage
The power supply voltage increases to the rated
national value.