Home » CEEFAX disks » telesoftware17.adl » 04-08-89/TVInfo
04-08-89/TVInfo
This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.
Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.
| Tape/disk: | Home » CEEFAX disks » telesoftware17.adl |
| Filename: | 04-08-89/TVInfo |
| Read OK: | ✔ |
| File size: | 1354 bytes |
| Load address: | 0000 |
| Exec address: | 0000 |
File contents
INTRODUCTION.
Being a tv repair technician I had requirements for test display patterns
to facilitate the assessment, repair and alignment of video display units.
I have attempted to structure this program to cover these requirements
based on practical experience.
The limitations of using the BBC computer for display alignment is rather
obvious - it does not cover the whole screen. A border exists at both
north-south and east-west of the display. I have not included a set of
colour bars which also show black and white,as white at the extreme west
of the display cannot be displayed, making grey scale tracking not
possible. Also I have not included a full test card as is usual with this
type of program as it is simply a compilation of individual patterns that
are already available.
A. CROSS-HATCH AND CIRCLE.
This is to align the red, green and blue guns, so as not to show overlap.
The circle can also show incorrect setting of the height controls.
* There is a conflict of requirements here, as the aspect of a tv set is
slightly different to that of a computer monitor - the subject of several
articles published in the "Electronics And Wireless World". The TVAlign
routine has been modified since its broadcast last January to produce a
true circle on a correctly adjusted computer monitor, thanks to Roger
Goodman of E.E. & W.W.
B. DOTS.
This as very much the same requirements as the cross-hatch, only much more
critical.
C.EHT.
Unfortunately we are still stuck with the cathode ray tube display and
consequently EHT voltages at the final anode. (as much as 25k. volts on a
26in tube). if beam current flows with peak whites the EHT voltage drops.
With a rapid drop in EHT volts this in turn causes electrons attracted to
the final anode of the CRT to expand - a process known as 'breathing'.
Normal commercial tv'S do not bother too much with correction circuits,
they simply over scan so that 'breathing' is not as noticeable. This is
not really desirable with a computer monitor and depends upon the degree
of sophistication to control the regulation of the EHT voltage in the
circuitry design. Regulating very high voltages can be expensive. Watch
the border lines, especially east-west.
D.CHROMA BARS.
All manufacturers of colour tv's publish service manuals of their products
which includes fault tracing and alignment of the colour decoder.
Oscilloscope reproductions are used to show the display at critical test
points on the circuit. Assuming correct working of the circuit, injecting
these chroma bars at the aerial or at composite video, will show the
correct oscilloscope displays. With a set of standard colour bars either
transmitted or generated in a purpose built unit, white is shown at the
extreme west and black is shown at the extreme east of the display. As
both black and white represent zero voltage at the decoder, alignment can
be achieved with this display.
E.HIGH FREQUENCY.
The output of random lower case letters in mode0 shows lack of high
frequency bandwidth. A VDU with RGB input should display this screen with
good definition.
F.RGB RASTERS.
Red, green, blue and white rasters are necessary for detecting and
aligning colour purity of the cathode ray tube. This is achieved by
adjusting the coils on the neck of the CRT and should only be attempted by
a trained technician.
G.COMPLEMENTARY COLOURS.
Should a PAL colour decoder have a fault, usually associated with the
'ident' circuits, this can be readily detected by the incorrect colours
being displayed. ie, blue for yellow and yellow for blue. Blue being the
complementary colour for yellow. etc.
H.PAL CROSS-COLOUR.
It must be remembered that our present PAL colour television system is
based on technology available over 20 years ago and has certain inherent
faults. One of these was lack of available bandwidth to transmit both the
luminance and chroma information separately. Consequently the chroma
sidebands are placed at the high frequency end of the luminance spectrum.
The luminance is, to a degree-depending on circuitry filters decoded by
the chroma decoder circuits; causing 'cross colour'. I have included this
pattern to demonstrate the difference with the signal encoded in PAL and
subsequently decoded at the PAL colour decoder. This would mean injecting
it at the aerial socket or at composite VIDEO or not encoding and decoding
PAL by using the RGB facility if available. If this is possible you may
like to try this and 'vive la difference!'. Looking to the future, the
coming of satellite tv, encoded with the D-MAC format- will see the
ellimination of this problem.
I.CHEQUERED BOARD.
This display will show overall leniarity of the raster. Lack of low
frequency response will be noticeable by the black squares smearing into
the whites.
J.DECAY.
Should the display appear to persist after switch-off, then the tube is
ageing. A replacement tube may be required.
BRIAN WEBB.
00000000 0d 49 4e 54 52 4f 44 55 43 54 49 4f 4e 2e 0d 0d |.INTRODUCTION...| 00000010 42 65 69 6e 67 20 61 20 74 76 20 72 65 70 61 69 |Being a tv repai| 00000020 72 20 74 65 63 68 6e 69 63 69 61 6e 20 49 20 68 |r technician I h| 00000030 61 64 20 72 65 71 75 69 72 65 6d 65 6e 74 73 20 |ad requirements | 00000040 66 6f 72 20 74 65 73 74 20 64 69 73 70 6c 61 79 |for test display| 00000050 20 70 61 74 74 65 72 6e 73 0d 74 6f 20 66 61 63 | patterns.to fac| 00000060 69 6c 69 74 61 74 65 20 74 68 65 20 61 73 73 65 |ilitate the asse| 00000070 73 73 6d 65 6e 74 2c 20 72 65 70 61 69 72 20 61 |ssment, repair a| 00000080 6e 64 20 61 6c 69 67 6e 6d 65 6e 74 20 6f 66 20 |nd alignment of | 00000090 76 69 64 65 6f 20 64 69 73 70 6c 61 79 20 75 6e |video display un| 000000a0 69 74 73 2e 0d 49 20 68 61 76 65 20 61 74 74 65 |its..I have atte| 000000b0 6d 70 74 65 64 20 74 6f 20 73 74 72 75 63 74 75 |mpted to structu| 000000c0 72 65 20 74 68 69 73 20 70 72 6f 67 72 61 6d 20 |re this program | 000000d0 74 6f 20 63 6f 76 65 72 20 74 68 65 73 65 20 72 |to cover these r| 000000e0 65 71 75 69 72 65 6d 65 6e 74 73 0d 62 61 73 65 |equirements.base| 000000f0 64 20 6f 6e 20 70 72 61 63 74 69 63 61 6c 20 65 |d on practical e| 00000100 78 70 65 72 69 65 6e 63 65 2e 0d 0d 54 68 65 20 |xperience...The | 00000110 6c 69 6d 69 74 61 74 69 6f 6e 73 20 6f 66 20 75 |limitations of u| 00000120 73 69 6e 67 20 74 68 65 20 42 42 43 20 63 6f 6d |sing the BBC com| 00000130 70 75 74 65 72 20 66 6f 72 20 64 69 73 70 6c 61 |puter for displa| 00000140 79 20 61 6c 69 67 6e 6d 65 6e 74 20 69 73 20 72 |y alignment is r| 00000150 61 74 68 65 72 0d 6f 62 76 69 6f 75 73 20 2d 20 |ather.obvious - | 00000160 69 74 20 64 6f 65 73 20 6e 6f 74 20 63 6f 76 65 |it does not cove| 00000170 72 20 74 68 65 20 77 68 6f 6c 65 20 73 63 72 65 |r the whole scre| 00000180 65 6e 2e 20 41 20 62 6f 72 64 65 72 20 65 78 69 |en. A border exi| 00000190 73 74 73 20 61 74 20 62 6f 74 68 0d 6e 6f 72 74 |sts at both.nort| 000001a0 68 2d 73 6f 75 74 68 20 61 6e 64 20 65 61 73 74 |h-south and east| 000001b0 2d 77 65 73 74 20 6f 66 20 74 68 65 20 64 69 73 |-west of the dis| 000001c0 70 6c 61 79 2e 20 49 20 68 61 76 65 20 6e 6f 74 |play. I have not| 000001d0 20 69 6e 63 6c 75 64 65 64 20 61 20 73 65 74 20 | included a set | 000001e0 6f 66 0d 63 6f 6c 6f 75 72 20 62 61 72 73 20 77 |of.colour bars w| 000001f0 68 69 63 68 20 61 6c 73 6f 20 73 68 6f 77 20 62 |hich also show b| 00000200 6c 61 63 6b 20 61 6e 64 20 77 68 69 74 65 2c 61 |lack and white,a| 00000210 73 20 77 68 69 74 65 20 61 74 20 74 68 65 20 65 |s white at the e| 00000220 78 74 72 65 6d 65 20 77 65 73 74 0d 6f 66 20 74 |xtreme west.of t| 00000230 68 65 20 64 69 73 70 6c 61 79 20 63 61 6e 6e 6f |he display canno| 00000240 74 20 62 65 20 64 69 73 70 6c 61 79 65 64 2c 20 |t be displayed, | 00000250 6d 61 6b 69 6e 67 20 67 72 65 79 20 73 63 61 6c |making grey scal| 00000260 65 20 74 72 61 63 6b 69 6e 67 20 6e 6f 74 0d 70 |e tracking not.p| 00000270 6f 73 73 69 62 6c 65 2e 20 41 6c 73 6f 20 49 20 |ossible. Also I | 00000280 68 61 76 65 20 6e 6f 74 20 69 6e 63 6c 75 64 65 |have not include| 00000290 64 20 61 20 66 75 6c 6c 20 74 65 73 74 20 63 61 |d a full test ca| 000002a0 72 64 20 61 73 20 69 73 20 75 73 75 61 6c 20 77 |rd as is usual w| 000002b0 69 74 68 20 74 68 69 73 0d 74 79 70 65 20 6f 66 |ith this.type of| 000002c0 20 70 72 6f 67 72 61 6d 20 61 73 20 69 74 20 69 | program as it i| 000002d0 73 20 73 69 6d 70 6c 79 20 61 20 63 6f 6d 70 69 |s simply a compi| 000002e0 6c 61 74 69 6f 6e 20 6f 66 20 69 6e 64 69 76 69 |lation of indivi| 000002f0 64 75 61 6c 20 70 61 74 74 65 72 6e 73 20 74 68 |dual patterns th| 00000300 61 74 0d 61 72 65 20 61 6c 72 65 61 64 79 20 61 |at.are already a| 00000310 76 61 69 6c 61 62 6c 65 2e 20 0d 0d 41 2e 20 43 |vailable. ..A. C| 00000320 52 4f 53 53 2d 48 41 54 43 48 20 41 4e 44 20 43 |ROSS-HATCH AND C| 00000330 49 52 43 4c 45 2e 0d 54 68 69 73 20 69 73 20 74 |IRCLE..This is t| 00000340 6f 20 61 6c 69 67 6e 20 74 68 65 20 72 65 64 2c |o align the red,| 00000350 20 67 72 65 65 6e 20 61 6e 64 20 62 6c 75 65 20 | green and blue | 00000360 67 75 6e 73 2c 20 73 6f 20 61 73 20 6e 6f 74 20 |guns, so as not | 00000370 74 6f 20 73 68 6f 77 20 6f 76 65 72 6c 61 70 2e |to show overlap.| 00000380 0d 54 68 65 20 63 69 72 63 6c 65 20 63 61 6e 20 |.The circle can | 00000390 61 6c 73 6f 20 73 68 6f 77 20 69 6e 63 6f 72 72 |also show incorr| 000003a0 65 63 74 20 73 65 74 74 69 6e 67 20 6f 66 20 74 |ect setting of t| 000003b0 68 65 20 68 65 69 67 68 74 20 63 6f 6e 74 72 6f |he height contro| 000003c0 6c 73 2e 0d 0d 2a 20 54 68 65 72 65 20 69 73 20 |ls...* There is | 000003d0 61 20 63 6f 6e 66 6c 69 63 74 20 6f 66 20 72 65 |a conflict of re| 000003e0 71 75 69 72 65 6d 65 6e 74 73 20 68 65 72 65 2c |quirements here,| 000003f0 20 61 73 20 74 68 65 20 61 73 70 65 63 74 20 6f | as the aspect o| 00000400 66 20 61 20 74 76 20 73 65 74 20 69 73 0d 73 6c |f a tv set is.sl| 00000410 69 67 68 74 6c 79 20 64 69 66 66 65 72 65 6e 74 |ightly different| 00000420 20 74 6f 20 74 68 61 74 20 6f 66 20 61 20 63 6f | to that of a co| 00000430 6d 70 75 74 65 72 20 6d 6f 6e 69 74 6f 72 20 2d |mputer monitor -| 00000440 20 74 68 65 20 73 75 62 6a 65 63 74 20 6f 66 20 | the subject of | 00000450 73 65 76 65 72 61 6c 0d 61 72 74 69 63 6c 65 73 |several.articles| 00000460 20 70 75 62 6c 69 73 68 65 64 20 69 6e 20 74 68 | published in th| 00000470 65 20 22 45 6c 65 63 74 72 6f 6e 69 63 73 20 41 |e "Electronics A| 00000480 6e 64 20 57 69 72 65 6c 65 73 73 20 57 6f 72 6c |nd Wireless Worl| 00000490 64 22 2e 20 54 68 65 20 54 56 41 6c 69 67 6e 0d |d". The TVAlign.| 000004a0 72 6f 75 74 69 6e 65 20 68 61 73 20 62 65 65 6e |routine has been| 000004b0 20 6d 6f 64 69 66 69 65 64 20 73 69 6e 63 65 20 | modified since | 000004c0 69 74 73 20 62 72 6f 61 64 63 61 73 74 20 6c 61 |its broadcast la| 000004d0 73 74 20 4a 61 6e 75 61 72 79 20 74 6f 20 70 72 |st January to pr| 000004e0 6f 64 75 63 65 20 61 0d 74 72 75 65 20 63 69 72 |oduce a.true cir| 000004f0 63 6c 65 20 6f 6e 20 61 20 63 6f 72 72 65 63 74 |cle on a correct| 00000500 6c 79 20 61 64 6a 75 73 74 65 64 20 63 6f 6d 70 |ly adjusted comp| 00000510 75 74 65 72 20 6d 6f 6e 69 74 6f 72 2c 20 74 68 |uter monitor, th| 00000520 61 6e 6b 73 20 74 6f 20 52 6f 67 65 72 0d 47 6f |anks to Roger.Go| 00000530 6f 64 6d 61 6e 20 6f 66 20 45 2e 45 2e 20 26 20 |odman of E.E. & | 00000540 57 2e 57 2e 0d 20 20 20 20 20 20 0d 42 2e 20 44 |W.W.. .B. D| 00000550 4f 54 53 2e 0d 54 68 69 73 20 61 73 20 76 65 72 |OTS..This as ver| 00000560 79 20 6d 75 63 68 20 74 68 65 20 73 61 6d 65 20 |y much the same | 00000570 72 65 71 75 69 72 65 6d 65 6e 74 73 20 61 73 20 |requirements as | 00000580 74 68 65 20 63 72 6f 73 73 2d 68 61 74 63 68 2c |the cross-hatch,| 00000590 20 6f 6e 6c 79 20 6d 75 63 68 20 6d 6f 72 65 0d | only much more.| 000005a0 63 72 69 74 69 63 61 6c 2e 0d 20 20 20 0d 43 2e |critical.. .C.| 000005b0 45 48 54 2e 0d 55 6e 66 6f 72 74 75 6e 61 74 65 |EHT..Unfortunate| 000005c0 6c 79 20 77 65 20 61 72 65 20 73 74 69 6c 6c 20 |ly we are still | 000005d0 73 74 75 63 6b 20 77 69 74 68 20 74 68 65 20 63 |stuck with the c| 000005e0 61 74 68 6f 64 65 20 72 61 79 20 74 75 62 65 20 |athode ray tube | 000005f0 64 69 73 70 6c 61 79 20 61 6e 64 0d 63 6f 6e 73 |display and.cons| 00000600 65 71 75 65 6e 74 6c 79 20 45 48 54 20 76 6f 6c |equently EHT vol| 00000610 74 61 67 65 73 20 61 74 20 74 68 65 20 66 69 6e |tages at the fin| 00000620 61 6c 20 61 6e 6f 64 65 2e 20 28 61 73 20 6d 75 |al anode. (as mu| 00000630 63 68 20 61 73 20 32 35 6b 2e 20 76 6f 6c 74 73 |ch as 25k. volts| 00000640 20 6f 6e 20 61 0d 32 36 69 6e 20 74 75 62 65 29 | on a.26in tube)| 00000650 2e 20 69 66 20 62 65 61 6d 20 63 75 72 72 65 6e |. if beam curren| 00000660 74 20 66 6c 6f 77 73 20 77 69 74 68 20 70 65 61 |t flows with pea| 00000670 6b 20 77 68 69 74 65 73 20 74 68 65 20 45 48 54 |k whites the EHT| 00000680 20 76 6f 6c 74 61 67 65 20 64 72 6f 70 73 2e 0d | voltage drops..| 00000690 57 69 74 68 20 61 20 72 61 70 69 64 20 64 72 6f |With a rapid dro| 000006a0 70 20 69 6e 20 45 48 54 20 76 6f 6c 74 73 20 74 |p in EHT volts t| 000006b0 68 69 73 20 69 6e 20 74 75 72 6e 20 63 61 75 73 |his in turn caus| 000006c0 65 73 20 65 6c 65 63 74 72 6f 6e 73 20 61 74 74 |es electrons att| 000006d0 72 61 63 74 65 64 20 74 6f 0d 74 68 65 20 66 69 |racted to.the fi| 000006e0 6e 61 6c 20 61 6e 6f 64 65 20 6f 66 20 74 68 65 |nal anode of the| 000006f0 20 43 52 54 20 74 6f 20 65 78 70 61 6e 64 20 2d | CRT to expand -| 00000700 20 61 20 70 72 6f 63 65 73 73 20 6b 6e 6f 77 6e | a process known| 00000710 20 61 73 20 27 62 72 65 61 74 68 69 6e 67 27 2e | as 'breathing'.| 00000720 0d 4e 6f 72 6d 61 6c 20 63 6f 6d 6d 65 72 63 69 |.Normal commerci| 00000730 61 6c 20 74 76 27 53 20 64 6f 20 6e 6f 74 20 62 |al tv'S do not b| 00000740 6f 74 68 65 72 20 74 6f 6f 20 6d 75 63 68 20 77 |other too much w| 00000750 69 74 68 20 63 6f 72 72 65 63 74 69 6f 6e 20 63 |ith correction c| 00000760 69 72 63 75 69 74 73 2c 0d 74 68 65 79 20 73 69 |ircuits,.they si| 00000770 6d 70 6c 79 20 6f 76 65 72 20 73 63 61 6e 20 73 |mply over scan s| 00000780 6f 20 74 68 61 74 20 27 62 72 65 61 74 68 69 6e |o that 'breathin| 00000790 67 27 20 69 73 20 6e 6f 74 20 61 73 20 6e 6f 74 |g' is not as not| 000007a0 69 63 65 61 62 6c 65 2e 20 54 68 69 73 20 69 73 |iceable. This is| 000007b0 0d 6e 6f 74 20 72 65 61 6c 6c 79 20 64 65 73 69 |.not really desi| 000007c0 72 61 62 6c 65 20 77 69 74 68 20 61 20 63 6f 6d |rable with a com| 000007d0 70 75 74 65 72 20 6d 6f 6e 69 74 6f 72 20 61 6e |puter monitor an| 000007e0 64 20 64 65 70 65 6e 64 73 20 75 70 6f 6e 20 74 |d depends upon t| 000007f0 68 65 20 64 65 67 72 65 65 0d 6f 66 20 73 6f 70 |he degree.of sop| 00000800 68 69 73 74 69 63 61 74 69 6f 6e 20 74 6f 20 63 |histication to c| 00000810 6f 6e 74 72 6f 6c 20 74 68 65 20 72 65 67 75 6c |ontrol the regul| 00000820 61 74 69 6f 6e 20 6f 66 20 74 68 65 20 45 48 54 |ation of the EHT| 00000830 20 76 6f 6c 74 61 67 65 20 69 6e 20 74 68 65 0d | voltage in the.| 00000840 63 69 72 63 75 69 74 72 79 20 64 65 73 69 67 6e |circuitry design| 00000850 2e 20 52 65 67 75 6c 61 74 69 6e 67 20 76 65 72 |. Regulating ver| 00000860 79 20 68 69 67 68 20 76 6f 6c 74 61 67 65 73 20 |y high voltages | 00000870 63 61 6e 20 62 65 20 65 78 70 65 6e 73 69 76 65 |can be expensive| 00000880 2e 20 57 61 74 63 68 0d 74 68 65 20 62 6f 72 64 |. Watch.the bord| 00000890 65 72 20 6c 69 6e 65 73 2c 20 65 73 70 65 63 69 |er lines, especi| 000008a0 61 6c 6c 79 20 65 61 73 74 2d 77 65 73 74 2e 0d |ally east-west..| 000008b0 0d 44 2e 43 48 52 4f 4d 41 20 42 41 52 53 2e 20 |.D.CHROMA BARS. | 000008c0 0d 41 6c 6c 20 6d 61 6e 75 66 61 63 74 75 72 65 |.All manufacture| 000008d0 72 73 20 6f 66 20 63 6f 6c 6f 75 72 20 74 76 27 |rs of colour tv'| 000008e0 73 20 70 75 62 6c 69 73 68 20 73 65 72 76 69 63 |s publish servic| 000008f0 65 20 6d 61 6e 75 61 6c 73 20 6f 66 20 74 68 65 |e manuals of the| 00000900 69 72 20 70 72 6f 64 75 63 74 73 0d 77 68 69 63 |ir products.whic| 00000910 68 20 69 6e 63 6c 75 64 65 73 20 66 61 75 6c 74 |h includes fault| 00000920 20 74 72 61 63 69 6e 67 20 61 6e 64 20 61 6c 69 | tracing and ali| 00000930 67 6e 6d 65 6e 74 20 6f 66 20 74 68 65 20 63 6f |gnment of the co| 00000940 6c 6f 75 72 20 64 65 63 6f 64 65 72 2e 0d 4f 73 |lour decoder..Os| 00000950 63 69 6c 6c 6f 73 63 6f 70 65 20 72 65 70 72 6f |cilloscope repro| 00000960 64 75 63 74 69 6f 6e 73 20 61 72 65 20 75 73 65 |ductions are use| 00000970 64 20 74 6f 20 73 68 6f 77 20 74 68 65 20 64 69 |d to show the di| 00000980 73 70 6c 61 79 20 61 74 20 63 72 69 74 69 63 61 |splay at critica| 00000990 6c 20 74 65 73 74 0d 70 6f 69 6e 74 73 20 6f 6e |l test.points on| 000009a0 20 74 68 65 20 63 69 72 63 75 69 74 2e 20 41 73 | the circuit. As| 000009b0 73 75 6d 69 6e 67 20 63 6f 72 72 65 63 74 20 77 |suming correct w| 000009c0 6f 72 6b 69 6e 67 20 20 6f 66 20 74 68 65 20 63 |orking of the c| 000009d0 69 72 63 75 69 74 2c 20 69 6e 6a 65 63 74 69 6e |ircuit, injectin| 000009e0 67 0d 74 68 65 73 65 20 63 68 72 6f 6d 61 20 62 |g.these chroma b| 000009f0 61 72 73 20 61 74 20 74 68 65 20 61 65 72 69 61 |ars at the aeria| 00000a00 6c 20 6f 72 20 61 74 20 63 6f 6d 70 6f 73 69 74 |l or at composit| 00000a10 65 20 76 69 64 65 6f 2c 20 77 69 6c 6c 20 73 68 |e video, will sh| 00000a20 6f 77 20 74 68 65 0d 63 6f 72 72 65 63 74 20 6f |ow the.correct o| 00000a30 73 63 69 6c 6c 6f 73 63 6f 70 65 20 64 69 73 70 |scilloscope disp| 00000a40 6c 61 79 73 2e 20 57 69 74 68 20 61 20 73 65 74 |lays. With a set| 00000a50 20 6f 66 20 73 74 61 6e 64 61 72 64 20 63 6f 6c | of standard col| 00000a60 6f 75 72 20 62 61 72 73 20 65 69 74 68 65 72 0d |our bars either.| 00000a70 74 72 61 6e 73 6d 69 74 74 65 64 20 6f 72 20 67 |transmitted or g| 00000a80 65 6e 65 72 61 74 65 64 20 69 6e 20 61 20 70 75 |enerated in a pu| 00000a90 72 70 6f 73 65 20 62 75 69 6c 74 20 75 6e 69 74 |rpose built unit| 00000aa0 2c 20 77 68 69 74 65 20 69 73 20 73 68 6f 77 6e |, white is shown| 00000ab0 20 61 74 20 74 68 65 0d 65 78 74 72 65 6d 65 20 | at the.extreme | 00000ac0 77 65 73 74 20 61 6e 64 20 62 6c 61 63 6b 20 69 |west and black i| 00000ad0 73 20 73 68 6f 77 6e 20 61 74 20 74 68 65 20 65 |s shown at the e| 00000ae0 78 74 72 65 6d 65 20 65 61 73 74 20 6f 66 20 74 |xtreme east of t| 00000af0 68 65 20 64 69 73 70 6c 61 79 2e 20 41 73 0d 62 |he display. As.b| 00000b00 6f 74 68 20 62 6c 61 63 6b 20 61 6e 64 20 77 68 |oth black and wh| 00000b10 69 74 65 20 72 65 70 72 65 73 65 6e 74 20 7a 65 |ite represent ze| 00000b20 72 6f 20 76 6f 6c 74 61 67 65 20 61 74 20 74 68 |ro voltage at th| 00000b30 65 20 64 65 63 6f 64 65 72 2c 20 61 6c 69 67 6e |e decoder, align| 00000b40 6d 65 6e 74 20 63 61 6e 0d 62 65 20 61 63 68 69 |ment can.be achi| 00000b50 65 76 65 64 20 77 69 74 68 20 74 68 69 73 20 64 |eved with this d| 00000b60 69 73 70 6c 61 79 2e 0d 0d 45 2e 48 49 47 48 20 |isplay...E.HIGH | 00000b70 46 52 45 51 55 45 4e 43 59 2e 0d 54 68 65 20 6f |FREQUENCY..The o| 00000b80 75 74 70 75 74 20 6f 66 20 72 61 6e 64 6f 6d 20 |utput of random | 00000b90 6c 6f 77 65 72 20 63 61 73 65 20 6c 65 74 74 65 |lower case lette| 00000ba0 72 73 20 69 6e 20 6d 6f 64 65 30 20 73 68 6f 77 |rs in mode0 show| 00000bb0 73 20 6c 61 63 6b 20 6f 66 20 68 69 67 68 0d 66 |s lack of high.f| 00000bc0 72 65 71 75 65 6e 63 79 20 62 61 6e 64 77 69 64 |requency bandwid| 00000bd0 74 68 2e 20 41 20 56 44 55 20 77 69 74 68 20 52 |th. A VDU with R| 00000be0 47 42 20 69 6e 70 75 74 20 73 68 6f 75 6c 64 20 |GB input should | 00000bf0 64 69 73 70 6c 61 79 20 74 68 69 73 20 73 63 72 |display this scr| 00000c00 65 65 6e 20 77 69 74 68 0d 67 6f 6f 64 20 64 65 |een with.good de| 00000c10 66 69 6e 69 74 69 6f 6e 2e 0d 0d 46 2e 52 47 42 |finition...F.RGB| 00000c20 20 52 41 53 54 45 52 53 2e 0d 52 65 64 2c 20 67 | RASTERS..Red, g| 00000c30 72 65 65 6e 2c 20 62 6c 75 65 20 61 6e 64 20 77 |reen, blue and w| 00000c40 68 69 74 65 20 72 61 73 74 65 72 73 20 61 72 65 |hite rasters are| 00000c50 20 6e 65 63 65 73 73 61 72 79 20 66 6f 72 20 64 | necessary for d| 00000c60 65 74 65 63 74 69 6e 67 20 61 6e 64 0d 61 6c 69 |etecting and.ali| 00000c70 67 6e 69 6e 67 20 63 6f 6c 6f 75 72 20 70 75 72 |gning colour pur| 00000c80 69 74 79 20 6f 66 20 74 68 65 20 63 61 74 68 6f |ity of the catho| 00000c90 64 65 20 72 61 79 20 74 75 62 65 2e 20 54 68 69 |de ray tube. Thi| 00000ca0 73 20 69 73 20 61 63 68 69 65 76 65 64 20 20 62 |s is achieved b| 00000cb0 79 0d 61 64 6a 75 73 74 69 6e 67 20 74 68 65 20 |y.adjusting the | 00000cc0 63 6f 69 6c 73 20 6f 6e 20 74 68 65 20 6e 65 63 |coils on the nec| 00000cd0 6b 20 6f 66 20 74 68 65 20 43 52 54 20 61 6e 64 |k of the CRT and| 00000ce0 20 73 68 6f 75 6c 64 20 6f 6e 6c 79 20 62 65 20 | should only be | 00000cf0 61 74 74 65 6d 70 74 65 64 20 62 79 0d 61 20 74 |attempted by.a t| 00000d00 72 61 69 6e 65 64 20 74 65 63 68 6e 69 63 69 61 |rained technicia| 00000d10 6e 2e 0d 20 20 20 0d 47 2e 43 4f 4d 50 4c 45 4d |n.. .G.COMPLEM| 00000d20 45 4e 54 41 52 59 20 43 4f 4c 4f 55 52 53 2e 0d |ENTARY COLOURS..| 00000d30 53 68 6f 75 6c 64 20 61 20 50 41 4c 20 63 6f 6c |Should a PAL col| 00000d40 6f 75 72 20 64 65 63 6f 64 65 72 20 68 61 76 65 |our decoder have| 00000d50 20 61 20 66 61 75 6c 74 2c 20 75 73 75 61 6c 6c | a fault, usuall| 00000d60 79 20 61 73 73 6f 63 69 61 74 65 64 20 77 69 74 |y associated wit| 00000d70 68 20 74 68 65 0d 27 69 64 65 6e 74 27 20 63 69 |h the.'ident' ci| 00000d80 72 63 75 69 74 73 2c 20 74 68 69 73 20 63 61 6e |rcuits, this can| 00000d90 20 62 65 20 72 65 61 64 69 6c 79 20 64 65 74 65 | be readily dete| 00000da0 63 74 65 64 20 62 79 20 74 68 65 20 69 6e 63 6f |cted by the inco| 00000db0 72 72 65 63 74 20 63 6f 6c 6f 75 72 73 0d 62 65 |rrect colours.be| 00000dc0 69 6e 67 20 64 69 73 70 6c 61 79 65 64 2e 20 69 |ing displayed. i| 00000dd0 65 2c 20 62 6c 75 65 20 66 6f 72 20 79 65 6c 6c |e, blue for yell| 00000de0 6f 77 20 61 6e 64 20 79 65 6c 6c 6f 77 20 66 6f |ow and yellow fo| 00000df0 72 20 62 6c 75 65 2e 20 42 6c 75 65 20 62 65 69 |r blue. Blue bei| 00000e00 6e 67 20 74 68 65 0d 63 6f 6d 70 6c 65 6d 65 6e |ng the.complemen| 00000e10 74 61 72 79 20 63 6f 6c 6f 75 72 20 66 6f 72 20 |tary colour for | 00000e20 79 65 6c 6c 6f 77 2e 20 65 74 63 2e 0d 20 20 20 |yellow. etc.. | 00000e30 0d 48 2e 50 41 4c 20 43 52 4f 53 53 2d 43 4f 4c |.H.PAL CROSS-COL| 00000e40 4f 55 52 2e 0d 49 74 20 6d 75 73 74 20 62 65 20 |OUR..It must be | 00000e50 72 65 6d 65 6d 62 65 72 65 64 20 74 68 61 74 20 |remembered that | 00000e60 6f 75 72 20 70 72 65 73 65 6e 74 20 50 41 4c 20 |our present PAL | 00000e70 63 6f 6c 6f 75 72 20 74 65 6c 65 76 69 73 69 6f |colour televisio| 00000e80 6e 20 73 79 73 74 65 6d 20 69 73 0d 62 61 73 65 |n system is.base| 00000e90 64 20 6f 6e 20 74 65 63 68 6e 6f 6c 6f 67 79 20 |d on technology | 00000ea0 61 76 61 69 6c 61 62 6c 65 20 6f 76 65 72 20 32 |available over 2| 00000eb0 30 20 79 65 61 72 73 20 61 67 6f 20 61 6e 64 20 |0 years ago and | 00000ec0 68 61 73 20 63 65 72 74 61 69 6e 20 69 6e 68 65 |has certain inhe| 00000ed0 72 65 6e 74 0d 66 61 75 6c 74 73 2e 20 4f 6e 65 |rent.faults. One| 00000ee0 20 6f 66 20 74 68 65 73 65 20 77 61 73 20 6c 61 | of these was la| 00000ef0 63 6b 20 6f 66 20 61 76 61 69 6c 61 62 6c 65 20 |ck of available | 00000f00 62 61 6e 64 77 69 64 74 68 20 74 6f 20 20 74 72 |bandwidth to tr| 00000f10 61 6e 73 6d 69 74 20 62 6f 74 68 20 74 68 65 0d |ansmit both the.| 00000f20 6c 75 6d 69 6e 61 6e 63 65 20 61 6e 64 20 63 68 |luminance and ch| 00000f30 72 6f 6d 61 20 69 6e 66 6f 72 6d 61 74 69 6f 6e |roma information| 00000f40 20 73 65 70 61 72 61 74 65 6c 79 2e 20 43 6f 6e | separately. Con| 00000f50 73 65 71 75 65 6e 74 6c 79 20 74 68 65 20 63 68 |sequently the ch| 00000f60 72 6f 6d 61 0d 73 69 64 65 62 61 6e 64 73 20 61 |roma.sidebands a| 00000f70 72 65 20 70 6c 61 63 65 64 20 61 74 20 74 68 65 |re placed at the| 00000f80 20 68 69 67 68 20 66 72 65 71 75 65 6e 63 79 20 | high frequency | 00000f90 65 6e 64 20 6f 66 20 74 68 65 20 6c 75 6d 69 6e |end of the lumin| 00000fa0 61 6e 63 65 20 73 70 65 63 74 72 75 6d 2e 0d 54 |ance spectrum..T| 00000fb0 68 65 20 6c 75 6d 69 6e 61 6e 63 65 20 69 73 2c |he luminance is,| 00000fc0 20 74 6f 20 61 20 64 65 67 72 65 65 2d 64 65 70 | to a degree-dep| 00000fd0 65 6e 64 69 6e 67 20 6f 6e 20 63 69 72 63 75 69 |ending on circui| 00000fe0 74 72 79 20 66 69 6c 74 65 72 73 20 64 65 63 6f |try filters deco| 00000ff0 64 65 64 20 62 79 0d 74 68 65 20 63 68 72 6f 6d |ded by.the chrom| 00001000 61 20 64 65 63 6f 64 65 72 20 63 69 72 63 75 69 |a decoder circui| 00001010 74 73 3b 20 63 61 75 73 69 6e 67 20 27 63 72 6f |ts; causing 'cro| 00001020 73 73 20 63 6f 6c 6f 75 72 27 2e 20 49 20 68 61 |ss colour'. I ha| 00001030 76 65 20 69 6e 63 6c 75 64 65 64 20 74 68 69 73 |ve included this| 00001040 0d 70 61 74 74 65 72 6e 20 74 6f 20 64 65 6d 6f |.pattern to demo| 00001050 6e 73 74 72 61 74 65 20 74 68 65 20 64 69 66 66 |nstrate the diff| 00001060 65 72 65 6e 63 65 20 77 69 74 68 20 74 68 65 20 |erence with the | 00001070 73 69 67 6e 61 6c 20 65 6e 63 6f 64 65 64 20 69 |signal encoded i| 00001080 6e 20 50 41 4c 20 61 6e 64 0d 73 75 62 73 65 71 |n PAL and.subseq| 00001090 75 65 6e 74 6c 79 20 64 65 63 6f 64 65 64 20 61 |uently decoded a| 000010a0 74 20 74 68 65 20 50 41 4c 20 63 6f 6c 6f 75 72 |t the PAL colour| 000010b0 20 64 65 63 6f 64 65 72 2e 20 54 68 69 73 20 77 | decoder. This w| 000010c0 6f 75 6c 64 20 6d 65 61 6e 20 69 6e 6a 65 63 74 |ould mean inject| 000010d0 69 6e 67 0d 69 74 20 61 74 20 74 68 65 20 61 65 |ing.it at the ae| 000010e0 72 69 61 6c 20 73 6f 63 6b 65 74 20 6f 72 20 61 |rial socket or a| 000010f0 74 20 63 6f 6d 70 6f 73 69 74 65 20 56 49 44 45 |t composite VIDE| 00001100 4f 20 6f 72 20 6e 6f 74 20 65 6e 63 6f 64 69 6e |O or not encodin| 00001110 67 20 61 6e 64 20 64 65 63 6f 64 69 6e 67 0d 50 |g and decoding.P| 00001120 41 4c 20 62 79 20 75 73 69 6e 67 20 74 68 65 20 |AL by using the | 00001130 20 52 47 42 20 66 61 63 69 6c 69 74 79 20 69 66 | RGB facility if| 00001140 20 61 76 61 69 6c 61 62 6c 65 2e 20 49 66 20 74 | available. If t| 00001150 68 69 73 20 69 73 20 70 6f 73 73 69 62 6c 65 20 |his is possible | 00001160 79 6f 75 20 6d 61 79 0d 6c 69 6b 65 20 74 6f 20 |you may.like to | 00001170 74 72 79 20 74 68 69 73 20 61 6e 64 20 27 76 69 |try this and 'vi| 00001180 76 65 20 6c 61 20 64 69 66 66 65 72 65 6e 63 65 |ve la difference| 00001190 21 27 2e 20 4c 6f 6f 6b 69 6e 67 20 74 6f 20 74 |!'. Looking to t| 000011a0 68 65 20 66 75 74 75 72 65 2c 20 74 68 65 0d 63 |he future, the.c| 000011b0 6f 6d 69 6e 67 20 6f 66 20 73 61 74 65 6c 6c 69 |oming of satelli| 000011c0 74 65 20 74 76 2c 20 65 6e 63 6f 64 65 64 20 77 |te tv, encoded w| 000011d0 69 74 68 20 74 68 65 20 44 2d 4d 41 43 20 66 6f |ith the D-MAC fo| 000011e0 72 6d 61 74 2d 20 77 69 6c 6c 20 73 65 65 20 74 |rmat- will see t| 000011f0 68 65 0d 65 6c 6c 69 6d 69 6e 61 74 69 6f 6e 20 |he.ellimination | 00001200 6f 66 20 74 68 69 73 20 70 72 6f 62 6c 65 6d 2e |of this problem.| 00001210 0d 0d 49 2e 43 48 45 51 55 45 52 45 44 20 42 4f |..I.CHEQUERED BO| 00001220 41 52 44 2e 0d 54 68 69 73 20 64 69 73 70 6c 61 |ARD..This displa| 00001230 79 20 77 69 6c 6c 20 73 68 6f 77 20 6f 76 65 72 |y will show over| 00001240 61 6c 6c 20 6c 65 6e 69 61 72 69 74 79 20 6f 66 |all leniarity of| 00001250 20 74 68 65 20 72 61 73 74 65 72 2e 20 4c 61 63 | the raster. Lac| 00001260 6b 20 6f 66 20 6c 6f 77 0d 66 72 65 71 75 65 6e |k of low.frequen| 00001270 63 79 20 72 65 73 70 6f 6e 73 65 20 77 69 6c 6c |cy response will| 00001280 20 62 65 20 6e 6f 74 69 63 65 61 62 6c 65 20 62 | be noticeable b| 00001290 79 20 74 68 65 20 62 6c 61 63 6b 20 73 71 75 61 |y the black squa| 000012a0 72 65 73 20 73 6d 65 61 72 69 6e 67 20 69 6e 74 |res smearing int| 000012b0 6f 0d 74 68 65 20 77 68 69 74 65 73 2e 0d 0d 4a |o.the whites...J| 000012c0 2e 44 45 43 41 59 2e 0d 53 68 6f 75 6c 64 20 74 |.DECAY..Should t| 000012d0 68 65 20 64 69 73 70 6c 61 79 20 61 70 70 65 61 |he display appea| 000012e0 72 20 74 6f 20 70 65 72 73 69 73 74 20 61 66 74 |r to persist aft| 000012f0 65 72 20 73 77 69 74 63 68 2d 6f 66 66 2c 20 74 |er switch-off, t| 00001300 68 65 6e 20 20 74 68 65 20 74 75 62 65 20 69 73 |hen the tube is| 00001310 0d 61 67 65 69 6e 67 2e 20 41 20 72 65 70 6c 61 |.ageing. A repla| 00001320 63 65 6d 65 6e 74 20 74 75 62 65 20 6d 61 79 20 |cement tube may | 00001330 62 65 20 72 65 71 75 69 72 65 64 2e 0d 20 20 0d |be required.. .| 00001340 20 20 20 20 20 20 20 20 42 52 49 41 4e 20 57 45 | BRIAN WE| 00001350 42 42 2e 0d |BB..| 00001354
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.