Apple II Display Monitors
Csa2 FAQs-on-Ground file: CSA2MONITOR.TXT rev010
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____________________________
001- How can I fix an unstable display?
002- I'm using a TV + IIc RF module. How can I improve the display?
003- What monitor repair Safety precautions are recommended?
004- How do I discharge the High Voltage anode?
005- How do I open my RGB monitor's case and get set for repairs?
006- What tools and solder should I use for repairs?
007- What's the fix for a flickering, Jumping, display?
008- How can I fix an all-red, all-blue, etc. monitor display?
009- Is there any more RGB Adjustments info?
010- How do I adjust Centering on my GS RGB color monitor?
011- How do I adjust Focus & Intensity on a blurry GS RGB Monitor?
012- What is a replacement for the RGB "flyback" power transistor?
013- How do I fix sporatic Shrinking and Flicking in-out of Focus?
014- How do I fix a serious case of shimmy on my GS monitor?
015- Will the Amiga 1084 monitor work on my GS?
016- What is the pinout for Commodore's 1084s monitor?
017- What is a "composite video monitor"?
018- Why doesn't hires look as good on my GS RGB monitor?
019- How can I to do the "Color Killer Mod" on a //e?
020- My A2 display doesn't work with a "TV/Game Switch". How come?
021- Can I use a color TV with my IIc+?
022- What is the IIc+ video pin configuration?
023- Where can I buy a replacement RGB monitor for my GS?
024- What kind of RGB monitors will work with a IIc?
025- Can I replace my GS RGB monitor with one from a PC?
026- What are the specs and pin-out for the GS RGB monitor?
027- Do I need monochrome monitor to get a clear 80-col display?
028- Is there a high-quality replacement for RGB monitors?
029- Can I use a GS RGB monitor with my IIc?
030- Why does a composite monitor I added show a fuzzy dim display?
031- Is my SecondSight board the cause of increased system crashes?
032- Why do Inwords and PublishIt bomb on my SecondSight board?
033- How many dots are actually sent to the GS monitor per line?
034- My GS RGB monitor takes a long time to get bright. A fix?
Monitor Repair Mini-Manual (Q&A 001-014) 4/98 version
This mini-manual describes Repairs & Adjustments which usually
involve removing the case. Before removing the case, check to see that
the your problems are not due to a poorly connected monitor cable or
misadjusted monitor controls.
From: Rubywand
001- My display is sharp but it seems to be unstable. Is there
a quick, easy fix for this?
Maybe. First, check your cable connections to make sure they are
solid. Also, try diddling the side and back controls. Sometimes, these
become dirty or develop bad spots.
If diddling a control seems to cure or nearly cure an unstable,
jumping, etc. display, you can be fairly sure that a squirt of Control
Cleaner will help. The cleaner needs to reach the control's resistance
element-- the place where the wiper touches the carbon track in a
potentiometer-- and you should turn the control back and forth after
squirting the cleaner. Probably, you will need to remove the case to get
a good shot at the dirty control.
= = = = = = = = = = = = = =
002- My Apple IIc has the IIc RF modulator module and is connected
to a color TV through a TV/Game switch. The color is okay but
the display is more or less ragged depending on where I run
the cable. Is there a way to get a better, more stable display?
If you are using a plain hi-fi type cable to connect from your IIc
modulator to the TV/Game switch, then, changing to a video cable may
help. If you are using a much longer cable than necessary, try a
shorter cable.
Another popular trick is to form any unused length into one or more
loops (use wire ties or tape to hold the loops together). Wrapping
unused cable length around a ferrite or iron core (e.g. from an old
transformer) is a variation on the same idea.
= = = = = = = = = = = = = =
003- What Safety precautions should I take when working
on my monitor?
Basically: unplug the monitor and let sit for a day, wear goggles,
work on a non-conductive table surface, do not stress CRT neck.
Unplugging the monitor and letting it sit for a few hours reduces
the danger of shock from stored charges; it does not eliminate it. The
usual warning for this kind of work is AVOID touching two different
circuit points at the same time. Like, don't touch the metal chassis and
the conductive surface of the CRT at the same time.
WEAR protective GOGGLES. If you should, somehow, bump or stress the
CRT neck-- as in jumping when you get shocked-- it may break. The result
may be a peaceful THOOP! or the CRT may implode in a spray of glass.
(Avoid using the CRT's neck to support the monitor in any position.)
Work on a wooden or plastic-topped table with plenty of space. Try
to position yourself, tools, and the monitor so that when you get
'stung', the chances of breaking something are reduced.
As much as posible, avoid using heavy tools of any kind. An
inadvertant tap from a mini-screwdriver is much less likely to crack the
CRT than a bonk from a full-sized screwdriver or pair of pliers.
Rubber gloves are probably a good idea so long as they do not get
in the way. Of course, pointy connections and components can puncture
gloves.
It's a good idea to clip a wire to the chassis and touch the other
end to the conductive surface of the CRT a few times before doing any
work in order to drain off any charge there.
Note: Several places in a monitor or TV carry high enough voltages to
deliver an uncomfortable shock. Draining the charge from one point does
not guarantee that other points have been discharged.
===========================
From: Joe Walters
004- How do I discharge the High Voltage?
The HV charge (20,000+ volts) might not be much reduced by just waiting
a few hours (or days), especially if you are in a low humidity location
and the tube, etc., are of good quality. You can, probably, _reduce_ the
shock hazard by discharging the High Voltage at the anode. You can not,
really, expect to eliminate the shock hazard. (See WARNING below.)
1. There is a long wire (called the anode) that goes from the high
voltage power supply to the top of the tube where it is snapped
into a hole. You can't see the hole because there is a rubber
shield built onto the wire. The end of the wire goes to a metal
clip which, without the rubber shield, looks somewhat as below.
One squeezes the clip so the end slips into the hole in the tube.
--- ---
== \ / ===== back of CRT
\ / <-- metal clip (This is what your grounded
| screwdriver needs to touch.)
[|]
[|] insulated Anode lead going to HV module
[|]
Needless to say, UNPLUG the monitor before beginning. Simply
turning it off isn't good enough.
2. Get a clip lead and clip one end to a long slender screwdriver
3. Clip the other end to the metal chassis of the TV (i.e the
metal frame parts)
4. Carefully! slip the screwdriver tip under the rubber flap on the
top of the tube until it touches the internal wire that both
holds the anode wire in place and conducts electricity.
Step 4 may result in a somewhat loud "SNAP" as the tube is discharged.
Be prepared so you don't jump and break something.
WARNING: After "discharging", do _not_ assume that no High Voltage is
present. Almost certainly, some High Voltage remains or may reappear
over time.
===========================
From: Rubywand
005- How do I open my RGB monitor's case and get set for doing
internal adjustments or repairs?
Whatever it is you plan to fix, if you remove the monitor case, you
will probably need to unplug the cable running from the circuit board to
the Controls/Switch Module on the side of the case. Use 'whiteout',
nail polish, etc. to mark the position of the plug. In more detail ...
1. Unplug everything from the monitor & let it sit for a day.
2. Put on protective GOGGLES. Place the unit face down on a wooden or
plastic-topped surface with lots of space and good lighting. Remove the
the screws. Place the unit in nomal position.
3. Have a fat magazine ready. Slide the case off until you are able
to see the control leads plugged into the main board on the right side
of the case. Mark the plug position with 'white-out', nail polish, etc..
Unplug the connector.
4. Slide off the case while supporting the monitor and slide the fat
magazine under the circuit board to prop up the monitor from behind.
5. Discharge the HV (optional, but, generally, a good idea).
6. <Do adjustments, fixes on Monitor>
7. When done, reinstall the control assembly.
8. Still wearing GOGGLES, support the monitor, remove the magazine,
slide on the case, reconnect the plug, finish sliding on the case,
replace screws.
= = = = = = = = = = = = = =
006- What tools and solder should I use for repairs?
For any soldering use a good quality pencil-style iron rated at
25-40 watts with a holder and sponge. Use high quality (60/40 tin/lead
or better) rosin core solder (e.g. Kester "44" 20 gauge).
= = = = = = = = = = = = = =
007- How do fix a Flickering, Jumping, display which sometimes
collapses to a line?
If the monitor exhibits major flickering, periodic collapse of the
display to a line, etc., then it may help to know that a common source
of such problems is one or more bad connections where the High Voltage
module is joined to the main circuit board. (This module is the black
thing with a HV lead running to the CRT-- it's near the left, back. The
slotted nub controls in its case set Focus and base Intensity.) Often
these connections look okay because it is hard to see the small
fractures in the solder surrounding the pins.
The cure is to resolder all of the pins coming from the module (on
the under-side of the circuit board). Before doing the soldering, clip
a wire to the metal chassis and touch the other end to each HV module
pin and other points in the area. While soldering, avoid touching
anything conductive on the monitor with anything but the iron and
solder.
= = = = = = = = = = = = = =
008- Suddenly my monitor has an all-blue (all-red, etc.) screen!
How do I fix this?
You probably have a blown choke on the little chroma board mounted
to the back of the CRT. The choke will be connected to one of the
larger, R/G/B output transistors. Use an Ohmmeter to find the open
choke. Replace the bad choke with 'one like it' or brew your own: wind
about 25-30 turns of #30 wire on a small ferrite core.
A more detailed procedure is presented below ....
1. The part that causes the problem when it fails is a "choke" or
"inductor" , it is mounted on a small circuit board attached to the back
of the monitor tube itself. This part looks like a small blue ceramic
ball with two leads coming out the bottom, and is color coded for 10
microhenries.
2. There are three of these items on that circuit board, and if any one
of them fails, the symptom is a screen all of one color, with total loss
of any controls of the monitor. The parts are identified by number, and
what color the screen is will tell you which one to replace.
L6R2 for a Red screen
L6G2 for a Green screen
L6B2 for a Blue screen
3. You can probably get a 10 microhenry choke at Radio Shack, or it is
available for $1.28 (plus a $5 Handling charge) from Digikey Corporation
at (800) 344-4539. They take Mastercard, Visa, and C.O.D.. The Digikey
part number is M8025-ND.
4. After replacing this part, the monitor colors may need to be
readjusted via the small color trimpots on the same circuit board.
===========================
From: David Fretz
009- Any more RGB Adjustments info?
R13- RGB Intensity
C86- Horizontal Position on RGB
C85- NTSC Color Hue Adjustment
C45- NTSC Frequency Adjustment
===========================
From: James Poore
010- How do I adjust Centering on my GS RGB color monitor?
Color monitors do vertical and horzontal centering differently than
do monochrome monitors. Almost all color monitors have either a jumper
arrangement or actual centering controls, sometimes both. Centering
adjustments are usually located on the PCB with no access holes, so the
back will most likely have to be removed to get to them.
If your monitor uses jumpers, there should be 3 tabs that each
jumper can be connected to. For vertical adjustment the tabs should be
marked as 'up', 'down', and center. If your pix is too high, then you
would connect the jumper to the down tab. For horizontal adjustment the
three tabs should be marked 'left', 'center', and 'right'.
If your monitor has centering controls, then adjust for best
centering.
Many GS monitors use small tab switches to adjust centering. These
are located near the back of the main circuit board.
Adjustment of Vertical Size, etc. via shafts on back of GS monitor
can affect centering. For small changes, these adjustments may get the
job done.
Adjustment of Intensity and Focus (see below) can affect centering.
===========================
From: Rubywand
011- How do I adjust Focus and Intensity on a blurry
GS RGB Monitor?
These adjustments may also help cure display "bowing", etc..
Intensity and Focus controls are on the High Votage Module (black
module near back of circuit board) inside the case.
Follow procedure outlined earlier for safety (e.g. unplug, wait,
wear goggles, ...) and removing the case.
Note the position of the two controls on the HV Module (at the
left, back). Mark the back of the cover where handy access hole should
be. Take the case cover to another area (i.e. away from the exposed
CRT neck). Remove the control assembly from the right side of the
case.
Using a Dremel tool, hole saw, ... cut an approx. 1" diameter hole
in the back of the case. Use this opportunity to give the case interior
a good cleaning. (If you wash it, be very sure it's dry before
continuing.)
Reinstall the control assembly.
Put everything back.
Reconnect cable and AC cord. Turn on the computer & monitor. Let it
sit 10-20 minutes. Use the normal side of case controls to get the
brightest, 'decent-focus' picture you can obtain.
Using a plastic TV technician's tool (and flashlight if necessary)
adjust the Intensity and Focus controls (through the hole in back) on
the HV module to get a good looking display.
Work back and forth between the back and side controls. What you're
aiming for is a display with good brightness and sharp focus when the
side controls are near their middle positions.
Cover the back hole using a piece of duct tape, a large sticker,
etc.. (The opening is a potential shock hazard, especially if the
monitor is within reach of children.)
===========================
From: "John F. Reeves" and Sam Goldwasser
012- I need to replace the High Voltage "flyback" power transistor
in my Applecolor monitor. The part bears no manufacturer's
mark, just two lines of text:
D1650
7A
What part should I get?
The transistor is part Q502 on the PCB of the Applecolor RGB
monitor, manufactured in 1987. This is the only power transistor in the
HV section, the only one which is on a heat sink. ...."
D1650 is a 2SD1650 which crosses to an ECG2331. You should be able
to pick one up at your local electronics shop. Try MCM Electronics,
Dalbani, etc..
===========================
From: Rubywand
013- How can I fix sporatic Shrinking and Flicking
in-out of Focus?
Arcing from the metal brace to the HV module can cause the display
to momentarily shrink and flick out of focus.
Follow safety and setup procedures outlined earlier.
The cure is to bend the brace up enough to increase the arc path
and clean the surfaces involved. Apply HV dope to the brace and module
where distances are small.
If the case interior seems pretty clogged with dust and gunk, it's
a good idea to remove the side-mounted Controls/Switch (C/S) Module and
give the case a good washing. (Be very sure it is well dried before
replacing.) You should also clean the two controls on the C/S Module
with spray-in Control Cleaner.
Before putting the case back, this may be a good time to adjust
base Intensity and Focus (the two nub controls on the HV module).
Position the monitor so that screen is easy to see and the nub controls
are accessible.
Plug in the the C/S Module. Adjust the C/S Module controls to
center positions. Plug in the monitor to the computer. Get a Desktop
display with some text and icons. Use an insulated tool to adjust the
nub Intensity and Focus controls for maximum sharpness at 'normal'
viewing intensity. A magnifying glass is helpful to obtain max pixel
sharpness.
= = = = = = = = = = = = = =
014- Suddenly my GS monitor exhibits a serious case of display
shimmy which sometimes degenerates into jagged lines. How
can I fix this problem?
Side-to-side shimmy indicates that Horizontal lock is not stable.
A good fix try is to adjust Horizontal Hold (the "<- ->" knob/stub)
until the shimmy stops. This usually works unless 1- The HH control is
already at its extreme setting, 2- The HH control has 'dirty' or burn
spots at the position which would, ordinarily, be the correct setting,
3- The display stabilizes but ends up moved too far to the left or right
side of the screen.
If, adjusting Horizontal Hold does not fix the problem, you will
probably need to remove the case. For starters, this will let you squirt
some Control Cleaner into the HH control.
With the case removed, you will have access to some other controls
which may help solve the shimmy problem. Two are on the black High
Voltage module: one nub controls base Intensity; the other controls
Focus. There are also a couple small tab switches located near the back
edge of the main circuit board. One sets Horizontal position; the other
sets Vertical position.
If you reconnect the side controls and power cord, you will be able
to experiment with adjustments.
Working with monitor adjustments with the case removed requires
constant awareness of potential hazards. For example, you would connect
the AC power cord to the monitor _before_ plugging it into an AC socket.
The monitor needs to be on a plastic or wooden table with nearby clutter
removed. It may be easiest to support with the rear of the circuit board
resting on a thick magazine.
You should have one or two plastic TV technician tools. These are
rods with ends for turning slotted controls. (A whole set will cost a
few dollars at Radio Shack.) Such tools are handy for adjusting the
controls on the back of the HV module, for flipping the tab switches,
for tapping components you suspect may be loose, etc..
Note: If the HH control seems to have serious burn spots-- e.g. you
notice a crunchy feel when turning the knob-- you may have to get it
replaced in order to achieve a correct setting. Replacing such a control
is a job for someone with experience in working with monitors or TV's.
If you decide to do it, be sure to check safety and setup suggestions
listed earlier. De-solder the control, remove it, and take it to an
electronics parts seller to get a replacement.
Working with Horizontal Hold, the Horizontal tab switch, and the
Intensity control on the HV module, (and, maybe, the Focus control and
Vertical Size) you should be able to eliminate any shimmy and end up
with a properly sized and positioned display.
Note: On some monitors, you may have to trade-off Vertical Size in order
to get a stable display which retains good linearity.
Once the shimmy problem is cured and the display is the right size
and positioned correctly, work back and forth between the side controls
and Focus to get a sharp display.
======= End of Monitor Repair Mini-Manual =========
From: Michael Hickey
015- I need a new RGB monitor for my GS. Will the
Commodore Amiga 1084 monitor work?
I have good information that the AMIGA 1084s monitor will work with
the Apple IIgs. I have no information on the quality of the output, I've
seen some Amiga displays that look no better than your average colour
TV. Perhaps the local WAL-Mart will have a few in stock at a low price.
You will need to build your own DB9 to DB 15 cable.
1084s to IIgs
DB9 DB15
1 13
3 2
4 5
5 9
7 3
____________________________
From: Stefan Voss
016- What is the pinout for Commodore's 1084s monitor?
pin assignment of 1084S monitor:
pin # analog RGB signal
1 ground
2 ground
3 red
4 green
5 blue
6 not used
7 composite sync.
8 horizontal sync.
9 vertical sync.
____________________
\ 5 4 3 2 1 /
\ /
\ 9 8 7 6 /
-------------
I can't give any garantee!
____________________________
From: Rubywand
017- What is a "composite video monitor"?
A composite video monitor is a display which requires a composite
video signal such as that output by an Apple II computer. The signal is
called "composite" because it is a mix of Video, Horizontal Sync, and
Vertical Sync signals. A color composite video signal will, also,
include Color Burst. These signals are separated inside the monitor.
The cable for connecting such a monitor is a single wire surrounded
by insulation with an outer shield (usually braided copper) covered by
insulation. The inner wire carries the signal, the shield is at
'ground'. Often, each end of the cable has a standard RCA plug-- so; the
cable looks much like a normal audio hi-fi cable. (In fact, a decent
hi-fi cable will, often, work fine for connecting your Apple II to a
composite color monitor.)
The main differences between a hi-fi cable and one intended to
carry video signals are 1) the video cable usually has a better,
tighter shield; 2) the video cable is characterized for impedance
matching at, usually, 50 or 75 Ohms; and 3) the video cable exhibits
lower capacitance between the center lead and the shield.
You can connect your Apple II to a Monochrome or Color composite
video monitor.
----------------------------
018- When I play old hires games on my GS the RGB monitor display
does not look as good as my old Amdek Color-1 connected to
the II+. What's wrong?
Most hires displays look better on a composite color monitor, such
as the Amdek Color-1, than they do on the GS's RGB monitor. The
difference is even more striking for double-hires displays. (King's
Quest and Air Heart look much better on a Color-1 connected to a IIc+
than on an RGB monitor connected to the GS.)
What's wrong is that the GS's display circuits do just a passable
job of translating hires and double-hires into RGB form.
----------------------------
019- Does anybody know how to do the "Color Killer Mod"
on a //e?
It looks like you should be able to do a full-screen color-killer
on a IIe by using a general purpose NPN transistor (2N3904, 2N2222,
etc.) to shunt the Color Burst signal. The transistor's collector would
connect to the junction of R15 and R13; the emitter lead would go to
Ground. The transistor should be connected directly to the R15-R13
junction and ground.
The base lead would go through a 2k-3k Ohm resistor to an
annunciator output, such as An-3 at pin 12 on the 16-pin J-15 Game
connector. PEEKing the appropriate addresses should flip Color OFF and
ON.
The reason for qualifiers such as "looks like", etc. is that I have
not actually tried a mod like this on a IIe. Monitors are remarkably
sensitive to Color Burst. If the transistor does not do a good job of
shunting the signal, enough may get through to trigger Color-ON.
A more positve (but less easy) technique is to use a 74LS32 OR gate
to control flow of the 3.58MHz signal. The IC could be tack-soldered
onto U88 via its +5 and GND pins. U88 is the 74S02 which has the gate
which produces Color Burst.
Pin 12 of the 'S02 would be bent up and connected to the output of
an 'LS32 OR gate (e.g. pin 3). One of the OR gate's inputs (pin 2) would
go to Pin 12 of the 'S02 socket. The other (pin 1) would go to an
annunciator output.
Turning ON the annunciator forces the OR gate output to "1" and
eliminates Color Burst. Turning OFF the annunciator lets the OR gate
output follow the 3.58MHz signal and enables Color Burst.
----------------------------
020- I connected my IIe to a color TV using a Radio Shack
"TV/Game Switch" but it doesn't work. How come?
A "TV/Game" switch is, usually, intended to switch RF (radio
frequency) signals. For example, in the "TV" position it connects the
TV's VHF antenna input to the VHF antenna (e.g. the long "rabbit
ears"). This way, you can watch TV.
In the "Game" position it connects the TV's VHF antenna input to a
game machine's or computer's CH 3 or CH 4 output. To see the computer's
display, you need to set the TV Channel selector to the channel being
output by the computer.
The reason your setup does not work is that the IIe does not output
an RF signal. (In fact, no Apple II has built-in circuitry for
outputting an RF signal.) The IIe outputs composite video. Composite
video is pure video information like the kind output by a VCR through
the standard 'Yellow' cable. It produces a better, sharper image than
video which is converted to RF and fed into a TV's antenna input.
If your TV has a "Video In" plug, that is where you want to plug in
the IIe's video output. An alternative is to plug the IIe output into a
VCR's "Video In" and let the VCR take care of interfacing to the TV.
Getting an "RF Converter" ("TV Converter", etc.) module is another
way to go. For about $30 Radio Shack sells a box which will convert an
Apple II's video signal to RF on CH3 or CH4.
One thing to consider when looking for ways to connect to a color
TV is that you could end up wasting time and money better spent on just
getting a standard composite color monitor (like the Amdek Color-1) at a
local Apple II swap meet.
----------------------------
021- Can I use a color TV with my IIc+?
Yes. You can use one of the methods described above or you can use
the RF Modulator module especially designed for the IIc series.
The IIc RF module is formed to fit the IIc case and has a "CH3-CH4"
slide tab on the top. Once the module is plugged in and a cable run to
the TV's antenna inputs or to a TV/Game switch, you can get very nice,
colorful on-TV hires and double-hires displays.
____________________________
From: David Empson
022- I have a friend with an Apple IIc+ who wants to connect
an RGB monitor. What is the IIc+ video pin configuration?
First, I should correct a misconception: the video port on the back
of the IIc+ is _not_ an RGB port. It is a video expansion port, which
provides all of the internal video generation signals used by the
IIc/IIc+ which can be used to generate an alternative video output
signal.
The actual functions of the IIc video port are as follows:
1 TEXT Indicates text mode is active (spcl fn in DHR mode)
2 14M 14 MHz clock sigal
3 SYNC Horizontal and vertical sync
4 SEGB Vertical counter signal from IOU, or lo-res indication
5 1VSOUND Sound output (one volt peak-to-peak)
6 LDPS Video shift load enable
7 WNDW Active area display blanking
8 +12V +12 volts DC
9 PRAS RAM row address strobe
10 GR Graphics mode enable
11 SEROUT Serialized character generator output
12 NTSC Composite NTSC video output
13 GND Ground reference
14 VIDD7 Bit 7 of video shift latch (hires mode col shifting)
15 CREF Colour reference timing signal
These come from the IIc Technical Reference, both first and second
editions.
You cannot connect a monitor directly to the IIc video port (with
the possible exception of the the LCD display, or an NTSC monitor). To
produce RGB output (or anything else) from this port, you need an
external adaptor box.
This adaptor is not simple: it has to decode the colour information
from the NTSC video signal (or generate it by detecting the graphics
mode and monitoring bit patterns), generate appropriate sync signals,
etc.
I believe there is (or was) an RGB output adaptor for the IIc,
which should also work on the IIc+.
____________________________
From: James Stafford
023- Where can I buy a replacement RGB monitor for my GS?
Alltech Electronics sells RGB monitors that they specially set up
for the Apple II for arround $150.00 I believe. These monitors were
Attari monitors that they fixed to work on Aplle II's. Alltech also has
used Aplle RGB monitors. Quality Computers has monitors made by Magnavox
for the Apple II. The price of these RGB monitors is $300.00.
____________________________
From: David Empson
024- What kind of RGB monitors will work with a IIc and a
Laser 128?
I don't know about the Laser. The IIc doesn't have built-in RGB
output. Its video port provides several low-level timing signals which
allow RGB data to be decoded from the composite video signal (which is
also provided on the port), but this requires external hardware.
The "standard" IIc RGB adaptor (assuming there was one) would probably
have produced digital RGB output, the same as the Apple III and the
Apple IIe memory expansion cards with RGB output. With a digital RGB
monitor, standard digital logic levels (TTL) indicate whether a colour
(or colour weighting) is present or absent. One wire is required for
each bit of each primary colour.
The IIgs, on the other hand, produces an analog RGB signal - a voltage
on the Red, Green and Blue outputs represents the intensity of each
primary colour. Any number of shades of each colour can be supported, by
providing a finer resolution digital to analog converter within the
computer. The IIgs has 4-bit D-to-A for each primary colour. High-end
video cards on the Mac and PC (SVGA) use 8-bit D-to-A for each primary
colour.
Digital RGB monitors cannot be used with an Analog RGB signal (unless
comparators are used to generate a digital signal from the analog one).
Analog RGB monitors cannot normally be used with a Digital RGB signal,
but generating an analog signal is possible with a resistor network (an
example of this is given in the Apple III Owner's Guide). In some
cases, it may be possible to plug an Analog RGB monitor into a Digital
RGB output, but it won't produce the correct colours (when compared with
a Digital RGB monitor).
There are two common types of digital RGB monitor: one type will work
with the Apple III, Apple IIe (with RGB card), Apple IIc (with RGB
adaptor) and CGA on an IBM PC (different cables or adaptors are
required). This type has intensity and one bit each for red, green and
blue (16 colours in total).
The second type is usable with EGA. This has two bits each for red,
green and blue (64 colours in total). These monitors also have a higher
scan frequency than the first type, and cannot be used with an Apple II
(unless a card has been specially designed to use them).
Analog RGB monitors are mainly classified by the scan frequency and
resolution. The IIgs RGB monitor (A2M6014X) operates at similar
frequencies to television - around 15 kHz. Macintosh and VGA/SVGA RGB
monitors do not support such low scan rates, and typically work at about
30 kHz or higher. The Mac cannot use the IIgs RGB monitor, and the IIgs
cannot use Mac/VGA RGB monitors.
Some third-party multisync monitors will work on the Mac/VGA and IIgs,
but these are very rare now. Most multisyncs do not go as low as 15
kHz.
"15 kHz" and "30 kHz" refers to the horizontal scan frequency - Apple II
video output has a horizontal retrace roughly 15,000 times per second.
Vertical retrace is a different issue (it is much slower - usually 50 to
100 retraces per second), and most monitors are very flexible in the
supported vertical retrace rate, as far as I know.
This is also where "interlacing" comes in. Interlacing is a technique
which doubles the effective vertical resolution of the monitor, by
performing two vertical scans (fields) per frame, with a slight vertical
shift in the second field. The scan lines for the second field are
interleaved between the scan lines for the first field.
An interlaced display has more noticeable flicker than a non-interlaced
display with double the frame rate, because the phosphor is only lit
half as often.
For example, the Second Sight card will support a 400 line interlaced
mode with the IIgs RGB monitor. There will probably be noticeable
flicker in this mode (especially out of the corner of your eye).
This mode will have 60 fields (i.e. 30 frames) per second, whereas the
standard IIgs video output is non-interlaced with 60 frames per second
(but only 200 lines vertical resolution).
(I'm assuming 60 Hz mode - the IIgs also support 50 Hz mode, for use in
countries with 50 Hz mains supplies and TVs.)
Television also uses interlacing - with NTSC, there are 525 lines per
interlaced frame and 30 frames per second, with alternating lines being
scanned on each pass of the electron beam (262.5 lines per field, 60
fields per second).
PAL uses 625 lines per frame, usually at 50 frames per second (312.5
lines per field, 25 fields per second).
____________________________
From: Rubywand
025- Can I replace my GS RGB monitor with one from a PC?
Modern PC monitors have a Horizontal scan rate which is too high to
be compatible with the GS. Some users report success using some old PC
VGA monitors with a special adapter cable.
----------------------------
From: Steve Jensen
I just tried a Sony CPD 1302 multisych monitor on a GS and it works
perfectly. Very crisp picture. I used a standard cable from a Mac II.
____________________________
From: Rubywand
026- What are the specs and pin-out for the GS RGB monitor?
Max Resolution: 640 Horizontal dots x 200 Vertical dots
(200 lines of 640 dots)
Dot Pitch: .37mm
CRT Size: 12"/ 11.5" viewable
Video Bandwidth: 6.5MHz (+/- 1.5DB)
Scanning Frequencies
60Hz model 50Hz model
Horizontal: 15.734kHz 15.696kHz
Vertical: 60Hz 50Hz
Pin Function
1 Red video ground
2 Red composite video
3 Composite sync
4 (not used)
5 Green composite video
6 Green video ground
7 (not used)
8 (not used)
9 Blue composite video
10 (not used)
11 (not used)
12 (not used)
13 Blue video ground
14 (not used)
15 (not used)
Shell Shield ground
----------------------------
From: Mitchell Spector
The above specs show only maximum resolution when used with a plain
Apple IIgs. It has an interlaced mode which allows you to display
640x400, though it isn't going to be easy to look at for long periods of
time. You can see the interlaced mode if you have a VOC or Second Sight
card.
The viewable area on an Apple IIgs is probably a fair bit less than
12"/ 11.5" viewable when you take into account all the space reserved
by the border in all display modes. That probably makes it about 10"
viewable or so. If you hook up another video source (e.g. a
SuperNintendo) then you can use the entire 11.5", including what would
be the border area.
____________________________
From: Rubywand
027- Do I need to connect a monochrome monitor to my IIe to get
readable 80-column text?
Maybe not. Try turning down the "Color" control to get a B/W
display and adjusting Brightness and Contrast. This will, possibly, make
80-column text readable on your composite color monitor. Just how
readable will depend upon the particular monitor. On the popular Amdek
Color-1, readability is marginal at best. According to some user
reports, readability is decent on Apple's composite color monitor.
____________________________
From: Jim Krych (ab453@cleveland.Freenet.Edu)
028- Is there a high-quality replacement for RGB monitors?
Yes. It's called the "VideoTurtle." (What follows comes from a
Video Turtle advertisement.)
The VideoTurtle is a product that converts your RGB signal, known
as TV RGB-15.75KHz scan rate for NTSC, into S-Video! S-Video is an
enhanced form of TV with better clarity and resolution than the "TV" we
are all familiar with.
With your computer, the VideoTurtle, and an S-Video equipped TV,
you get equal or better display quality, than your old RGB monitor. Not
only that, you get a much bigger and eye-pleasing display, and a TV to
boot!
The VideoTurtle, from Turtle Enterprises, can be purchased for
$149.95 from one of it's authorized distributors, such as Tex Comp Ltd.
To order all 1-800-846-3474. For technical information on TV RGB systems
we haven't mentioned, or general technical help, call 1-626-967-3341.
Turtle Enterprises can be reached via email: videoturtle@hotmail.com
____________________________
From: Tony Cianfaglione
029- Can I use a GS RGB monitor with my IIc?
I use a IIc with a GS RGB monitor constantly through a Video 7
cable and it works fine. The 80 column text is crystal clear plus you
can make it 4 different colors by flipping switches on the Video 7. A
digital RGB displays 16 colors on a IIc but the GS RGB still displays 8.
____________________________
From: Rubywand
030- I connected a composite monitor to my GS at the standard "RCA
plug" output but I get a fuzzy dim display. The monitor worked
fine on my II+. What's the problem?
When a composite monitor is known to be okay, a fuzzy/dim display
usually indicates that the video output level is too low. (A too-bright,
whitish, faded look could indicate the output is too high.)
You can adjust video output on a II+ via the small on-mother knob
near the Game I/O socket. There does not seem to be any way to adjust
composite video output on the GS. If your monitor has a video input
level adjustment, try changing the setting.
----------------------------
031- Ever since adding a SecondSight video board it seems like my
GS is always crashing. Is the SS board causing problems?
SecondSight adds some nice features; but, it is known to be a power
hog. Most likely, your system is crashing due to noise glitches on the
+5V and/or +12V power busses. The fix is to fatten power supply leads
and, probably, add on-motherboard +5V and +12V jumpers to a couple
Slots. Details are supplied in the POWER FAQs (csa2POWER.TXT).
____________________________
From: James D. Keim
032- My SecondSight board bombs every time I try to run Inwords or
PublishIt. What's wrong?
Inwords and PublishIt use the DHR display. The SecondSight cannot
emulate the DHR display and locks up the system.
____________________________
From: Eric Jacobs
033- Including the left and right borders, how many dots are
actually sent per line in 320 and 640 modes on the GS?
Including the left and right borders, plus the horizontal retrace,
the video sends out more than 320 or 640 "dots" before the screen begins
scanning the next line. Here's a quick summary of the Apple II video
that's been used throughout the whole series (assuming 60 Hz video
here). It's a slightly modified NTSC signal, though the differences are
small enough for most monitors to accomodate.
Everything in the Apple II is derived from a 14.31818 MHz master
clock. This runs both the video and the processor/memory subsystems. The
cycle time is therefore 69.8 ns. For 640-mode (or 80 cols, or
double-hires) the dots are sent out at simply this rate. In 320-mode (40
cols or single-hires) the dots are sent out at half that rate, 7.15909
MHz (one pixel every 139.6 ns). The NTSC standard calls for 227.5 cycles
of color reference (3.579545 MHz) per horizontal line, for a horizontal
scan rate of 15.734 KHz (3.579545/.2275). The Apple II rounds this up to
228 cycles of 3M, so the horizontal scan rate is 15.699 KHz
(3.579545/.228). This is well within the tolerance of most monitors. So
therefore in 320-mode 228*2 = 456 "dots". In 640-mode there are 912
"dots". I put dots in quotes because, obviously, only 320 or 640 of them
are actually seen as part of the screen.
When the GS is outputting a composite video signal, each horizontal
line must contain a horizontal sync pulse and color burst, and there
can't be a border during this time, or else the TV won't register a
sync. On the RGB, the GS puts the border color on. So, the answer to
your question is 456-320 or 136 pixels in 320-mode and 912-640 or 272
pixels in 640-mode. This includes both borders and the horizontal sync.
Of course, a good proportion of this time is not visible; this depends
on the overscan settings of the particular monitor.
____________________________
From: Eric Jacobs
034- I picked up a IIgs RGB monitor at a garage sale. The focus is
off and it took several minutes until the display got brighter
but it's still not very good. Are there any adjustments that can
be made?
The problem you describe is consistant with low B+ going to the
flyback transformer which results in low brightness level, poor focus,
and blooming when the brightness and/or screen level is turned up. More
than likely if this monitor has been sitting around for awhile, the
filter capacitors have gone to mush. Sometimes they can be revived by
leaving the monitor on for a long period of time <over 24hrs> but,
usually, they require replacement.