AMAXNEW Descrambler (Elvis The Great) version 1.0b+
-------------------
This schematics is a tested version of the Amaxnew Descrambler v. 1.0b+
The descrambler is for sync suppressed systems WITHOUT INVERSION.
The descrambler takes into account the PDK pulses (missing horisontal
syncs) which also the maxinew/maxipic does.
When watching unscrambled channels the control signal
to the RF stage is minimized, so the channel is not affected. When
switching to scrambled channel, the analogue stage sets the control signal
to the RF stage to such level, which descrambles it.
I have built the additional stages on a veroboard for experimentation and
connected it to the Maxinew descrambler. The asm code should also be found
in this zip file.
The Amaxnew descrambler is based on Automax 1.0, which was reversed
engineered by ™rgen (Thanks for that !!! Truly great hack !)
and the Maxinew Descrambler (Elvis The Great)
Maxinew's design is based on Maxipic by Cableboss and Odin
(That's were it all started !)
Special thanks also to Hugobardu who has made great investigations into
the cable TV world, and revealed the secrets of many strange designs.
Thanks to Maxipic for the home page , and all the others contributing to
the designs, improvements, testing etc. !
Bill of Material for AMAXNEW.PCB (Hope this is ok!)
Comment Pattern Quantity Components
------------------------------------------------------------------------------
100K AXIAL0.4 2 R4, R7
1K AXIAL0.4 2 R13, R17
22K AXIAL0.4 1 R2
27R AXIAL0.4 2 R14, R15
2M2 AXIAL0.4 1 R8
2M7 AXIAL0.4 1 R5
10K AXIAL0.4 2 R3, R10
4M7 AXIAL0.4 2 R9, R11
68K AXIAL0.4 1 R6
6M8 AXIAL0.4 1 R12
75R AXIAL0.4 1 R1
100NF C 9 C7, C11, C12, C15, C16, C100,
C101, C102, C103
100PF C 1 C2
150pF C 1 C4
68PF C 1 C3
27pF C 1 C17
33 PF C 2 C5, C6, C19
330PF C 1 C10
10UF EK 2 C13, C14
47UF EK 1 C1
10K TRH1 1 RV2
25K TRH1 1 RV1
1N4148 D 6 D1, D2, D3, D4, D5, D6
4066 DIP14 1 IC4
4069 DIP14 1 IC2
8 MHZ XTAL1 1 XTAL
MC78L06 TR 1 IC5
PIC16F84 DIP18 1 IC1
TL084 DIP14 1 IC3
Here's some info about the sampling stage
The function of the Automax sampling stage (Örgen),
implemented into Amaxnew (Elvis The Great).
Please refer to the Amaxnew schematics.
The capacitors C7, C11 are charged through the R5,R9 resistors.
RA3 goes high for about 0.5 us, and samples the video signal
at color burst in HBI (horisontal blanking interval)
(color should actually be filtered away). This discharges the
C7 to black level of the video signal. In a scrambled picture
the black level in HBI is far above the original level.
RC signal goes high a bit in on each video line. This means that
the C11 cap. is discharged continously through D4 during the
video line.
The result is that the lowest level which occurs during the video line
will be at the input to IC3b.
IC3b and IC3a are voltage followers which outputs the same voltage
from the caps C7 and C11, and these output signals are going to
a differential integrator circuit, with a DC amplification
added (R11,C12,IC3c,R12).
The output signal of this stage is the DC correction signal to the RF stage.
The DC correction is sampled out to the RF during video line.
The R5-C7, and R9-C11, are slowly again charging, but the difference stays
constant. This difference is the key thing here, as this determines the
output signal to the RF stage. Another thing is the Resistor-caps
(RC) or integrating circuits:
The RC circuits (not the signal!) used in amaxnew makes
changes go slow, so this means that even if the black level in a
video line does not occur (due to the current picture is for instance white),
this does not affect the correction signal instantly. Small variations,
though, might occur, and in my case I note that a bright picture gives
a bit brighter picture and vice versa. It is though possible to watch
the picture without getting a high bloodpressure :-)
Some thoughts on the autolevel thing:
First some background info :
Automax by ™rgen
----------------
This was the original design from which the Amaxnew evolved (together
with Maxinew, which in turn was a mod from Maxipic by Cableboss
and Odin).
This device contains some 4538 monostables which
only have the possibility to give certain control signals to the
4066 gates.
Amaxnew
-------
Amaxnew design uses the Automax autolevel adjust stage, but in
the Amaxnew case we have a lot of more possibilities to make lots of
other control signals to the 4066 stages, as well as sampling almost
whatever we want in the video signal, because of the PIC processor.
Duck's ideas:
-------------
Duck (in a prev msg thread) shows that it is possible to make a
simplier autolevel stage, using less components. I studied the
ascii schematics, and would make some small mods, but the main idea
is great ! (If I were from England I would probably
yell "Marvellous"!)
I hereby suggest a mod which reduces even further the components
required. We still need 2 ICs to do the autolevel adjust,
but as Duck says, we can use a trimpot for setting black level to the
differential amp. which then should be more stable than the previous
designs.
It goes like this:
<pre>
VCC
| RA3 RA2
/ | |
\ 10K | |
/ | |
video | |------| |\ |
o--||------| 4066 |-------------|+\ |
in | |------| | | \ |------|
/ | | >---|-| 4066 |---- RF correction out
\ 10K Cs === | / | |------|
/ | |--|-/ |
| ___ | |/ |
| | |
--- | |
VCC | Ry |
| |--\/\/--- |
/ | |
\ 10K | |
/ | |
| | |
/ black level set | || |
10K \ <------------------/\/\/---|--||------|
pot. / Rx ||
| Cx
/
\ 10K
/
|
_|_
Control signals in comparison to the video lines:
|---HBI-----|------Video line ----------------|
| RA3 samples black level of HBI
|---------------------------------| RA2 opens gate to RF stage.
</pre>
It might be that there are some caps missing, for removing
glitches etc. and I'm not sure about the values of the differential
stage's Rx,Ry,Cx and the Cs but the main idea could work.
The idea : Setting video dc level to approx half the VCC,
sample back porch of horisontal blanking (Cs gets this voltage),
compare the thing with the differential stage and produce
the correction voltage. Sample out this to the RF when video line occurs.
As you might notice I've removed the diodes in the sample and hold
stages, as those were used in Automax for finding the lowest
level of the video line, and here I only want to compare the
HBI black level with the black level I get from the trimpot.
(One of the diodes in Automax was for balancing that stage with the
other as a diode makes the sample 0.7 V higher).
Some things must be taken into account when designing the above stage,
such as that 4066 has approx 1kohm impedance when active, and we must
make sure that the cap, which gets the sample voltage, does get charged
properly during the sampling (0.5 us), otherwise we'll have a low pass
filter there. The input cap combined with the 2* 10K, might work as
a high pass filter, reducing slow variations in the video, so this must also
checked. etc.etc.
Duck has tested some of the stages above and has come up with some great
results. It might be possible to use a much simplier stage.
Some thoughts on rf stages:
I tried to implement the Maxinick RF stage, but I could not control it
with the Automax stage so I changed back to the maxinew stage again.
The Amaxnew 1.0 b+ has been modified from a version containing some
design flaws, and have not been tested after that
Please report any bugs to the Maxipic discussion board. The link to the
board can be found at
http://members.xoom.com/Maxipic
TNX 2 all for their effort !
&
Keep up the brainstorming !
regards,
Elvis