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Track: summa.fail.a.sleep...;)
By: djz.hwc
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I somehow got a Gunfighter ega-monitor and
I decided to connect it to Spec. With this
purpose, the monitor was solemnly handed over
me to conduct experiments on it and
scientific research to identify
the ability to connect it to the ZX.
The monitor itself was quite small, with
15 inches, approx. When turned on
showed signs of life in the form of a launch
line scan unit. Unfortunately,
there were no other signs of work.
The screen was black, at least give it to this
monitor of what, at least not. Therefore it was decided
it was necessary to tighten the shortcut on the kinescope board
(if I'm not mistaken, it regulates
accelerating voltage). As a result
it became possible to change these manipulations
raster brightness from zero to uniform
white. Unfortunately, without
images and colors ;(
Then it was decided to disassemble the hell with this
monitor into its component parts, fortunately there
everything is located on the chassis and connected
connectors. True, with the quantity
fasteningelements manufacturers clearly
they overdid it and there were a lot of bolts
a lot.
As a result of the above actions
The monitor was disassembled into its component parts:
kinescope, board, power supply and housing.
Unfortunately, enable it in this form
turned out to be completely impossible, since
connecting wires in many places
were too short for all this
connect in disassembled form. Therefore
every time to check
the performance of the monitor, its
I had to put it back together ;)
So, we look from the connector along r, g, b.
Diodes and shortcuts are of little interest to us, although
they are simply scribbled on these signals
a huge variety.
What do we see? PLM'ku in the crib and
inverter After them - straight to the amplifiers
and kinescope. The kinescope turned out to be working
- this is the conclusion I made, one by one
tearing off the wires coming from the terminals
amplifiers for kinescope. Guns r, g and b
worked great :)
Then I decided to connect the ZX to the monitor
and measure the amplitude of the output signals
PLM'ki, i.e. at the terminal inputs
video amplifiers. There was a signal there, and
changed depending on what
the picture should be on the screen.
Therefore, the circuits up to the video amplifiers
OK. This makes me extraordinary
made me happy, although even ifthe whole tract
amplification of these signals is burnt out, you can
it would be easy to assemble an amplifier for each
one or two transistors. This is not for us
problem.
So. It has now become clear that
video amplifiers are faulty, and immediately
all three ;) This got me thinking,
that something is blocking them. Unfortunately,
there was no circuit diagram for this monitor, and
no blocking circuits in monitors, according to
idea, it shouldn't be.
Well... There is only one thing left -
select one amplifier and check
cascade after cascade. I must say
The monitor is designed very interestingly -
seven (!) transistors per amplifier...
This, you know, is something :) Let's go along the first one
cascade - the cascade is working, go to
the final one - there is no signal. Therefore,
middle.
Gunfighter just came in here :) K
fortunately, without beer ;)
I must say, the presence of someone
was not present during equipment repair
stimulates my thinking abilities
:) therefore, having received a pair from a friend
advice, I continued checking the work
cascades. Why check there if not?
I have an idea about the scheme?
Flipped through a book with diagrams
TVs, paying attention to
construction of final stages
video gain. ANDнашел одну похожую
схему:
She was very similar, but this
and it doesn't matter. But I understood how
these amplifiers are built in this model
monitor. Then everything became clear.
By the way, it should be noted that between
PLM'koy and video amplifiers (VA) stood
another amplification stage, at the same time there
the brightness was mixed. This canoe
fed from a separate source
voltage and was also working properly.
Well... I turn on the monitor and climb
probe through the terrifying appearance
line scan circuits, like myself
towering lineman and every now and then
crackling wires ;) and I see that
is on the terminals of one of the transistors. And
what do I see? But I see a zero on the base, although
in theory, there should be tension there,
close to the feeder.
- Take off the fee! - Gunfighter commands.
We check for short circuit - and that’s it! Something
short. We look along the paths and see
large 470 µF capacitor, in the diagram
it is highlighted and an arrow points to it.
We solder it - and that’s it. To the capacitor
cranks. What was unusually surprising
Gunfighter :)
With a proud look I take it out from my reserves
domesticcapacitor of the same
rating and voltage, only according to
gabatiram one and a half times larger ;) and
I solder it, having first straightened it
nearby radio elements to the sides :)
We can end here
narration, since the main
the fault has been corrected.
Yes, I almost forgot - signals r, g and b
must be fed to the monitor input
directly from the control center.
Now let's talk about how
convert a similar ega monitor to svga!
The prospect, I must say, is tempting,
but due to my lack of ega'shnogo
monitor for experiments, more
I can't give detailed recommendations ;)
I saw this technique on one of
Internet sites for hardware...
So, the most important thing is to increase
monitor line frequency from 15 to 37 kHz.
The second is to adapt the path
video signal processing, which is due to
digital input, not analogue, as in
svga.
To change the line you need to find
defining string generator, and next to it -
frequency-setting capacitor. Replace
it (with small TKE) to a capacitor with
lower denomination.
Close the base and emitter of the output
line transistor. To base
connect the buffer transistoroscilloscope. Set the frequency to 31 kHz.
Don't forget to check your parameters
line transistor - necessary
voltage about 1500 V, power 30
W and frequency from 30 MHz. Very desirable
presence of built-in damper diode
(2SCЗ883, BU2508, 2SCЧ769 are suitable).
Now you can remove the jumper between
base and emitter and connect to the gap
power scan resistor type PEV on
10...20 W nominal 20 Ohm.
Turn on the monitor. Possibly dim
narrow picture. If there is a twist
per screen, denomination required
capacitor parallel to the output
transistor (and the capacitor should
be 1600V type K78-2 or similar).
Then short-circuit the coil regulating
size of lines that stands in the OS break
and wind up half of the linearity regulator
lines.
In theory, a smooth line should appear, but
narrow picture. Now we will raise
line supply voltage
scans. If the monitor has
voltage 80-100V, then connect it
instead of 55 and be sure to change it in the power supply
diode along this line to a more powerful one
(for example, KD226).
After this, the size and brightness should
normalize, but don't forget to drive
monitor for overheating. If
The line transistor gets very hot,
install a radiatormore.
600 line mode in ega monitors
it's quite easy to get since there
frequency switching is 15/21 kHz
(in the primary winding of the lowercase
two transformers are switched
windings).
If the monitor is working normally and not
overheats, can be removed
limiting resistor and close
the place where it breaks.
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