jw@mck-csc.UUCP (Jeffrey Weiss) (07/04/90)
In recent weeks, someone posted some corrections to Radio Electronic's Descrambler (..er Sync Restorer) article. I've just read the article, and had a few q's for those of you who have used this project: The circuit takes video in and produces video out. I've noticed that on some scrambled stations (e.g., Sportschannel in NY), the audio is perfectly audible, while on others (e.g., HBO), it is not. What are the methods of hiding the audio, and are there any published references to restoring it? I noticed that Manhattan Cable in NY has announced that channels will no longer be available (after July 15) to customers unless they upgrade to the new digital box. Would this render the RE circuit obsolete? -- ...mit-eddie!mck-csc!jw Jeffrey Weiss
sb2o+@andrew.cmu.edu (Scott Klaus Boehmke) (02/06/91)
I too have found that the C24 is a touchy little bastard. However, when passing normal video through the device, I am able to make the unit sync up by turning up R34 to allow a very colorfull picture. This results in a smaller color burst level, and fewer things for the TV to have problems locking in on. I can then lower back down R34 to a normal color level, and the picture usually stays locked. Some observations noticed with the oscilloscope: Pin 8 of IC5 (the chroma chip) outputs garbage when the circuit powers up. Pin 7 (the clock signal from the 3.58 oscillator associated with C24) looses amplitude and lock when I touch C24 (makes sense eh?) As a result, I get no burst key from the CD22402, and no lockup. Something else I noted... Pin 9 of the PLL outputs a stable signal at all times (not surprising for a PLL) but the frequency changes once the circuit locks up to a slightly higher value. Keeping this in mind, I have tinkered with C36 (what I believe to be the initial frequency setter) but have not found any golden results. Anyone have any other ideas? I have also played with the value of C42 by placing various capacitors in parallel, and even removing it to put in a smaller fixed value, but no results other than failure to be able to lock up even with the button pressed. I believe that the value of the cap is correct, because the screen scrolls horizontally at a reasonable rate when S1 is pressed... what else does that leave? Thinking back now, the deal with adjusting R34 doesn't make all that much sense as far as the circuit locking up, because it only controls the level output to the TV, not the levels internal to the circuitry... hummmm.... The technical support number given by the company that sold the kit is 518-854-9280. Does anyone in that area code care to give the company a call? hours are 1:30-4:30 pm EST. Scott sb2o@andrew.cmu.edu
dth@cs.brown.edu (Dzung T. Hoang) (02/06/91)
In article <gbfhVDm00UgI0BcWha@andrew.cmu.edu> sb2o+@andrew.cmu.edu (Scott Klaus Boehmke) writes: >I too have found that the C24 is a touchy little bastard. However, when >passing normal video through the device, I am able to make the unit sync up >by turning up R34 to allow a very colorfull picture. This results in a smaller >color burst level, and fewer things for the TV to have problems locking in on. >I can then lower back down R34 to a normal color level, and the picture usually >stays locked. I had problems with sinc initially but the following modifications solved some of the problems: - replace both of the variable caps with Radio Shack #272-1340 the increase range (6-50pf) should help - use an offboard regulated switching power supply for all the voltages--remember those TI power supplies RS sold for $4.95? - use a clean video source--some of the newer VCR's do terrible things to the video output, as well as muting the audio - shield the board - use shielded cabling for the video input/output > >The technical support number given by the company that sold the kit is >518-854-9280. Does anyone in that area code care to give the company >a call? hours are 1:30-4:30 pm EST. > >Scott >sb2o@andrew.cmu.edu If the company you are refering to is D&D Electronics, I would advise you to call the number yourself. It would be worth the toll. The person on the other end is an independent techie who has a lot of experience, having built 100's of kits, and even has made mods/adds to the circuit to make it lock all the time automatically. Call for more details. ---------------------------------------------------------------------------- Dzung T. Hoang dth@cs.brown.edu ----------------------------------------------------------------------------
wood@drift.dec.com (John F. Wood) (02/06/91)
I posted this a while back, but I'm not sure if it got out or not. Anyway:
While poking around on the Radio Electronics BBS the other day, I found the
attached list of FAQs about the universal descrambler. I hope they help.
And I hope they don't mind that I posted it...
File name: descramb.txt
The following are the most frequently asked questions about the universal
descrambler/synch regenerator. A 20 Mhz scope and frequency counter are a
must for trouble shooting.
1. R7 There has been some confusion as to the correct connections around
R7 and the polarity switch S3. If one closely examines the PC board, R7 can
either return to +5V or to ground. R-E Fig3 and Fig4 (P40,41) seem in
conflict. If R7 is returned to ground then +5V is supplied through S3. If R7
is returned to +5V, then ground should be supplied through S3. Actually R7
was intended to either return to ground or +5V to allow various interfacing
methods for experiments in automatic polarity switching.
2. Pin 9 IC5 This pin will normally read +0.2 to +0.3 volts; not -0.2
volts as in R-E P43 Column 1. Q2 produces a narrow(2msec) positive going
pulse during burst intervals to IC5 pin 9 and therefore a VOM or DVM will read
only a very small positive voltage.
3. Pins 5 & 10 IC1 are -5V and +5V respectively.
4. The correct frequency signal at pin 23 IC9 is 503.496 khz (503.5 khz
nominal) not 1.08 Mhz as shown in R-E. The output from IC6 (divided by 455)
should be 7867.13 hz. If this is not the case, check D1-D6.
5. One must have a 4V to 5V P-P square wave at P23 (503.5 khz) before the
decoder will operate.
6. IC9 The voltage at pins 13, 11, and 5 may vary considerably or even
read zero, depending on the meter used to measure them. Verify 503 khz clock
is present on Pin 23 IC9.
7. IC8 divides by 64, not 128. Pin 12 shown is actually pin 2.
8. IC10 may run somewhat hot. Do not apply more than 15 vac to J3
without providing a heatsink on IC10. This heatsink is not provided with the
kit.
9. Ringing on picture - Check IC1 and verify that C2, C3, C4, and C5 are
in the circuit and OK. Try a .01 bypass between IC1 pin 14 and ground
(connect across R4)
10. -0.45 volts is supplied to IC3 Pin 2, not IC2 Pin 2 as in Column 1
page 43.
11. Locking of picture in some cases can be improved by changing R20 and
R21 (1K each) to 470 ohm. However, before doing this check C17, L1, Q1, R22,
R23, and C18.
12. Incorrect hue can be shifted to improve color by adding capacitance
(try 33 pf) across C32. If this makes things worse, then try changing C30
from 56 pf to 33 pf without the 33 pf across C32.
13. Color stability is a function of accurate lockup. The burst key pulse
(IC9 Pin 11) is somewhat narrow. Try resetting lock with S1. If no help,
make sure that the video signal is clean. Some experimenters have reported
that IC6 can produce "glitches" or momentary intermittent miscounting. A
change of value of R36 (try 1K ohm) and also of C36 (try values from 820 pf to
..0015 uf) has helped in these cases.
14. Smear may be caused by incorrect frequency response somewhere in the
video system. This is generally an interface problem. Try the following:
A Remove IC2 and IC3.
B Jumper IC2 pin 2 to pin 15 and IC3 pin 3 to pin 15.
C Now using a good off the air NTSC signal (not scrambled),
connect video into J1 and examine video out of J2. If OK, the problem is not
in the descrambler video circuit.
D restore normal connections and check IC2 and IC3. If OK, the
problem is in the video source. A typical case with a non-scrambled signal,
the picture is OK, but with a scrambled signal, there is smear, blotchy color,
shadowing,or poor contrast.
Remember that your VCR, TV tuner or video source may not operate properly with
a scrambled video signal. The horizontal and/or vertical pulse are missing or
distorted. Your equipment may contain circuitry that depends on these pulses
for some phase of operation (AGC, DC restoration, etc.) and therefore may
further distort a scrambled signal. The reconstituted signal may therefore
show these distortions. Therein were no such problems in the prototype
circuits, so there shouldn't be any problems inherent in the descrambler. The
following points should be considered:
A The video source should ideally be right off the video
detector of the TV tuner or receiver with no extra amplifiers or other
circuitry. Sag, excess tilt, or other waveform distortions can occur due to
low frequency response or phase shift in the coupling capacitors.
B The fact that "every else works OK without the descrambler in
the system" is meaningless due to the aforementioned considerations.
----------------------------------------------------------------------
John F. Wood | EIS Engineering
Digital Equipment Corporation | ARPAnet: wood@drift.enet.dec.com
Continental Blvd. | EASYnet: DRIFT::WOOD
MKO2-1/J12 | Usenet : ...!decwrl!drift!wood
Merrimack, NH 03054 | AT&T : (603) 884-4686
----------------------------------------------------------------------
Disclaimer: Views expressed herein are my own and do not necessarily
reflect those of my employer.
----------------------------------------------------------------------al@qiclab.scn.rain.com (Al Peterman) (02/07/91)
I just had an interesting chat with the fellow who D&D electronics refers
technical support to. His name is Tom Page. He has developed a modification
kit (or instructions - not sure which) for the universal descrambler. He
did give some ideas to help achieve stable lock-up over the phone.
1. Change the trimmer caps to Radio Shack 273-1340A.
2. Change R2 to 5K RS 271-1714.
3. Ground the case of the crystal to C22 ground.
4. Change C21 to 1 ufd.
5. Change c30 to 100pf
6. If necessary add a "hot shot" switch that grounds IC6-10 momentarily..
I suspect that grounding the crystal and the C21 & C30 changes may help..
For more info you can call Tom at 407-799-4292 or can order his mod's
at:
KDA
PO Box 320404
Coco Beach, FL 32932
I really don't know if his mod kit is worth the $10 he wants for it - but
then again if it works...
--
Alan L. Peterman (503)-684-1984 hm
al@qiclab.scn.rain.comckinsman@eecs.wsu.edu (Chris Kinsman - EE major) (02/07/91)
In article <63777@brunix.UUCP> dth@cs.brown.edu (Dzung T. Hoang) writes: > >If the company you are refering to is D&D Electronics, I would advise you to >call the number yourself. It would be worth the toll. The person on the >other end is an independent techie who has a lot of experience, having built >100's of kits, and even has made mods/adds to the circuit to make it lock >all the time automatically. Call for more details. > Could you verify that the above number is D&D Electronics. I would like to get a descrambler and need to find a source for a kit and/or completed ones for a REASONABLE price. Chris `
jhp@sactoh0.sac.ca.us (Jim H. Puga) (02/10/91)
I've finally decided to build the descrambler and have a quick
question. What does NPO stand for on capacitors? Is there
anything I should know before I start building this thing?
Thanks.
--
-------------------------------------------------------------
- Usenet : jhp@sactoh0.SAC.CA.US -
- UUCP : ames!pacbell!sactoh0!jhp (or so I've been told) -
"There's a lesson here somewhere." --Space Ghost bill@flutter.tv.tek.com (William K. McFadden) (02/12/91)
In article <1991Feb9.233031.25283@sactoh0.sac.ca.us> jhp@sactoh0.sac.ca.us (Jim H. Puga) writes: >I've finally decided to build the descrambler and have a quick >question. What does NPO stand for on capacitors? Is there >anything I should know before I start building this thing? It refers to the temperature characteristic of a ceramic capacitor. NP0 stands for "negative-positive zero," which means that the capacitance is not supposed to vary (much) with temperature. This is the best kind of temperature compensating capacitor. There are also non-temperature compensating types, which are used in applications where the value isn't critical (e.g., decoupling caps). One such type is Z5U. Z5 indicates a +10C to +85C temperature range, and U means +22%/-56% max. capacitance range over temperature. -- Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077 bill@videovax.tv.tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill Phone: (503) 627-6920 "SCUD: Shoots Crooked, Usually Destroyed"
myers@hpfcdj.HP.COM (Bob Myers) (02/12/91)
>I've finally decided to build the descrambler and have a quick >question. What does NPO stand for on capacitors? Is there >anything I should know before I start building this thing? "NPO" stands for "Negative-Positive-Zero" (if it stands for anything), and basically means a ceramic capacitor whose value changes very little with temperature. (I believe that "C5G" or something like that is the present designation for this.) Other ceramic dielectrics have other designators which signify their behavior vs. temperature; two common ones are X7R and Z5U, which are worse than NP0 vs. temperature. (Z5U is the worst - I think it's something like -20%/+80% or thereabouts over a 0-85 deg. C range. Z5U tends to be seen a lot on what are basically cheap, low-quality caps - as in lots of voids and other defects in the dielectric. I'd avoid them like the plague even if you can handle the lousy temp. coefficient.) Bob Myers KC0EW HP Graphics Tech. Div.| Opinions expressed here are not Ft. Collins, Colorado | those of my employer or any other myers@fc.hp.com | sentient life-form on this planet.
RWA1@psuvm.psu.edu (02/12/91)
my understandin about NPO is also "negative positive-zero". But this is not just that 'it's better'. I understand it to mean that it varies around the value. with a mean of the indicated value. The other options are not less than (and i forget the indications for these) and not greater than (and this is a rare bird). The purpose of an NPO would be to have a falue for a filter, for instance, where a "not less than" would be a bypass cap for digital circuits Rich Adamec once i did EE, now I profess it!
whit@milton.u.washington.edu (John Whitmore) (02/14/91)
In article <17660151@hpfcdj.HP.COM> myers@hpfcdj.HP.COM (Bob Myers) writes: >"NPO" stands for "Negative-Positive-Zero" (if it stands for anything), and >basically means a ceramic capacitor whose value changes very little with >temperature. > ... [other common ceramic capacitor types are] X7R and Z5U, which >are worse than NP0 vs. temperature. (Z5U is the worst - I think it's something >like -20%/+80% or thereabouts over a 0-85 deg. C range. Z5U tends to be seen >a lot on what are basically cheap, low-quality caps - as in lots of voids and >other defects in the dielectric. I'd avoid them like the plague even if you >can handle the lousy temp. coefficient.) I'd like to add that the high capacitance density of Z5U is attained by using ferroelectric materials. These are nonlinear in applied voltage, as well as 'drifty' in temperature, and in fact are also liable to flex like a piezoelectric crystal would, so have significant damping (i.e. never achieve good high Q). If you want losses at high frequencies, like in a bypass capacitor, they may be just what you want. But NEVER try 'em in a high-Q filter. I have changed the values by 3% on these jobbies just by laying a warm thumb alongside 'em. John Whitmore "Typically, capacitors with BX or X7R characteristic decrease in capacitance by approximately 10% when rated DC voltage is applied. Other formulations with very high dielectric constants may exhibit a capacitance decrease of 50%." --Kemet Capacitors General Catalog
grayt@Software.Mitel.COM (Tom Gray) (02/15/91)
In article <17660151@hpfcdj.HP.COM> myers@hpfcdj.HP.COM (Bob Myers) writes: >>I've finally decided to build the descrambler and have a quick >>question. What does NPO stand for on capacitors? Is there >>anything I should know before I start building this thing? > >"NPO" stands for "Negative-Positive-Zero" (if it stands for anything), and >basically means a ceramic capacitor whose value changes very little with >temperature. (I believe that "C5G" or something like that is the present I agree with Bob's statements here but maybe there is a need for a small qualification. I too thought that NPO was a classification of the temperature rating of a ceramic capacitor. However. I was told in no uncertain terms that NPO is a TYPE of ceramic used for capacitors. Examining a capacitor catalogue showed that this was the case. In short NPO capacitors have a low temperature coefficient but not all low temperature coefficient capacitors are NPO. I previously worked for a large company where the terms Z5U, Y5V NPO etc were used to describe caps of all types. It came as a complete surprise to me to find that NPO pertained to only one type of ceramic. A great electronic trivia question - stump your firends. . . . . . . .