Some useful circuits and adapters for 9-pin monitors and the systems that use them.
There are 4 types of monitors with 9-pin plugs:
Type 1: CGA, EGA and MDA PeeCee monitors. I'll ignore those here. They're shit 16 colour rubbish.
Type 2: Commodore 1084, Atari SC1435, Philips CM8833, etc. These are the monitors commonly used with Amigas and Atari STs. The most common, more than CGA/EGA/MDA.
Type 3: Some Acorn computers (and monitors?), some Taxan monitors, and IBM PGA cards and monitors. Uncommon. PGA uses a scan rate ~30kHz so is not compatible with SCART.
Type 4: Early IBM VGA cards and monitors, 9-pin. You can still buy 9-to-15 and 15-to-9 pin adapters between these two standards. Scan rate is ~30kHz so not compatible with SCART.
Then there's the popular SCART connector.
Type 3 and 4 are very similar and some monitors may support both standards. Some type 2 monitors support type 1 signals with a switch on the back.
This page has adapters and conversion circuits between these five types of connector.
This circuit connects a 1084/CM8833/SC1435 monitor cable to a SCART TV. Useful if you have cables for each computer already.
SCART plug, male
(rear view,
Audio in solder side)
2x phono (RCA) sockets +--------------+
Right | 1 == |
+----(O------------|-== 2 |
9 pin female D-sub Audio | | 3 == |
(rear view, ground +------------------|-== 4 |
solder side) | Left | 5 == |
+----(O------------|-== 6 |
+--\__ 3x 100uF 16V +--------------------|---------7-== |
| \__ + | Blue | == 8 |
| 5-----|-------------| |-+ | 9 == |
+-------------|------9 | + | == 10 |
| | 4-----|-------------| |----------------------|--------11-== |
| +-------|------8 | + Green | == 12 |
| | | 3-----|-------------| |-+ | 13 == |
| +-------|------7-|------+-----+ | Red | == 14 |
| +----|--2 | | | +--------------------|--------15-== |
| | | 6 | \ +------\/\/\--------------|-== 16 |
| +----|--1 __+ / 1K 330 ohms +---------|--------17-== |
| | | __/ \ | GND | == 18 |
| | +--/ |/| | |\| /Comp. sync | | 19 == |
+------------------------| |--+--| |-----+--------------------|-== 20 |
| |\| |/| | | /Comp. | _______##_|
| 1N4148 1N4148 / | | / |21
| \ 1K | |__/ |
| / | | Ground
+-------------------------------+----------+---------------------+
The TV won't switch over to SCART automatically, you need to select it manually.
You can substitute 1N4001 in place of 1N4148. Any diode, just not Schottky.
It matters which way round you put the diodes:
End with stripe
|
|\| V
----| |----
|/|
If you install the three capacitors on the R, G, B lines, it matters which way around you put those too:
Stripe indicates negative
|
V
___________
/ \========\----
\__/________/---- <-- +
The capacitors are optional. Might be required with some TV and computer combinations. Putting them in won't reduce compatibility.
Some models of Atari ST might want 120 ohm resistors in series with the R, G, B lines if the picture looks washed out. But that makes other systems too dark.
Pin 16 on SCART switches the TV to RGB mode. Some TVs can be switched manually. If so you can omit that resistor and pin.
The circuitry combines separate H and V sync and shifts levels.
Some TVs might lose their shit if they see the RGB select pin strobing. The SCART standard is supposed to support this! The solution:
1N4148
330 ohms |\|
From pin 7 on D-sub >-----\/\/\-----| |----+----> Pin 16 on SCART
|/| |
| +
-----
----- 100uF 16V
|
+----> Pin 17 on SCART
Some computer/TV combinations may not switch into RGB mode if not enough current from Vsync pin. If so, too bad. That's the price you pay for an unpowered adapter.
This circuit connects a SCART device to your Atari SC1435, Philips CM8833 or Acorn AFK17 monitor.
SCART plug, female
(rear view, Audio out
solder side) Left 2x phono (RCA) plugs
+--------------------------------O)----+
| |
| +--------------+ |
| | == 1 | Right |
| | 2 ==-|------------O)----+
| | == 3 | Audio ground | 9 pin D-sub male
| | 4 ==-|------------------+ (rear view,
| | ==-5---------|----+ solder side)
+----|---------6-== | | Blue
| ==-7---------|-----------------------+ __/--+
| 8 == | | | __/ |
| ==-9---------|----+ +-----------------|------5 |
| 10 == | | Green | 9 |
| ==-11--------|-----------------------------------------|------4 |
| 12 == | | | 8 |
| ==-13--------|----+ +-----------------|------3 |
| 14 ==-|----+ Red | +--------|--7 |
| ==-15--------|-----------------------+ | | 2-|--+
| 16 == | | | | 6 | |
| ==-17--------|----+ | +__ 1-|--+
| 18 ==-|----+ | \__ | |
| == 19 | | /Comp. sync | \--+ |
| 20 ==-|--------------------------------+ |
|_##_______ | | |
| 21 \ | | |
| \__| | Ground |
+----------------+------------------------------------------------+
The SCART device must output RGB. Not composite or S-video.
This diagram only works with Philips-made chassis! It will work with some C= 1084 monitors but not all! Definitely not shitty Daewoo-made ones. See below for alternative.
As above but works with all monitors (with the correct pinout).
SCART plug, female
(rear view, Audio out
solder side) Left 2x phono (RCA) plugs
+--------------------------------O)----+
| |
| +--------------+ |
| | == 1 | Right |
| | 2 ==-|------------O)----+
| | == 3 | Audio ground | 9 pin D-sub male
| | 4 ==-|------------------+ (rear view,
| | ==-5---------|----+ solder side)
+----|---------6-== | | Blue
| ==-7---------|--------------------------+ __/--+
+-------|---------8-== | | | __/ |
| | ==-9---------|----+ +--------------|------5 |
| | 10 == | | Green | 9 |
| | ==-11--------|-----------------------------------------|------4 |
| | 12 == | | | 8 |
| | ==-13--------|----+ +--------------|------3 |
| | 14 ==-|----+ Red | +----|--7 |
| | ==-15--------|--------------------------+ | | 2-|--+
| | 16 == | | | | 6 | |
| | ==-17--------|----+ | +__ 1-|--+
| | 18 ==-|----+ | \__ | |
| | == 19 | | | \--+ |
| +---|--------20-== | | | |
| | |_##_______ | | | |
| | | 21 \ | | | |
| | | \__| | Ground | |
| | +----------------+------------------------------------------------+
| | | |
| | +5-12V (from AV switching pin) | /Comp sync |
| | | out |
| | | |
| | Comp. | |
| | video +-------------------------------------+ |
| | in | |
| | | +---------+ | | |
| | 0.1 uF +----|.1 U 8 |--+----------------| |-----------------+
| | | | | | | | | |
| +--------| |----------| 2 7 | | 0.1 uF |
| | | | | | | |
| \ | 3 6 | | LM1881 or EL1881 |
| / 68 ohms | | | video sync separator |
| \ +----| 4 5 | | |
| | | +---------+ | |
| | | | |
| +-----------------+------------------------------------------------------+
| | |
| | |
+------> To 5V regulator | |
input (optional) | |
| |
| |
USB power +5V >-------------------------+ |
|
USB power ground >-----------------------------------------------------------+
The SCART device must output RGB. Not composite or S-video.
You need to supply USB power for it to work (see below for self-powering alternative). Take a USB cable and cut it in the middle. The red wire is usually +5V. Black is ground. Circumcise the green and white wires, the cosmetics industry needs them more than you do.
You want it to be self-powered from the SCART device? Fine, use this regulator:
C (pin 3) E (pin 1)
From SCART pin 8 >--+-----------------\ /---------+-----------> To LM1881/
| 2N3904 / 2N2222 \ ^ | EL1881
| / BC547* NPN --------- | pin 8
| transistor | B |
\ | (pin 2) |
/ 330 ohms | |
\ | |
| | \
+--------------------+ / 10k
Cathode (pin 3) | \
+-----+ Ref |
| | (pin 1) |
|TL431|---------+
| | |
+-----+ \
Anode (pin 2) | / 10k
| \
| |
Any ground >-----------------------------+------------+
(except audio
ground)
* Swap pin 1 and pin 3 if using BC547!!! i.e. install backwards
You can't use a 7805 regulator. Too much dropout voltage! Pin 8 can be between 5V and 12V. That's why the circuit's the way it is. If your SCART device is very non-standard and outputs no voltage on pin 8, it won't work.
Pin numbers for 2N3904, 2N2222, BC547, TL431:
_________
/Flat /|
/ face / /
/ / /
--------- /
\_/ / /_//
/ / /
1 2 3
Top view of LM1881/EL1881, legs down (pointing away from you):
+--- Pin 1 identified by dot in corner, and notch at top of chip
| |
V V
+-- --+
1 -|* U |- 8
2 -| |- 7
3 -| |- 6
4 -| |- 5
+------
If you plug your Amiga or ST into your monitor and get no signal or a blue picture without sync, use this.
9 pin female D-sub 9 pin D-sub male
(rear view, (rear view,
solder side) solder side)
To 1084-style cable To monitor
+--\__ __/--+
| \__ __/ |
| 5--------------------------------+ | 5 |
+---------------9 | | +-----9 |
| | 4-----------------------------+ | | | 4-----+
| +-----------8 | | | +-----8 | |
| | | 3--------------------------+ | +-------|---------3 | |
| +-----------7 | | | +-----7 | |
| | | 2----------+ | +----------|---------2 | |
| | | 6 | | | +-----6 | |
| | | 1----------+ +-------------|---------1 | |
| | | __/ | | \__ | |
| | +--/ | | \--+ |
| | | | |
| | | | |
| | /Comp. sync | Ground | |
| | or +----------------+------------+ |
| | /Hsync 330 ohms \ |
| +--------------\/\/\----+ / 10k |
| /Vsync |/| | |\| \ /Comp. sync |
+------------| |------------+----| |----+----------------------------+
|\| |/|
2x 1N4148 diodes
IBM PGA/PGC monitors expect a scan rate of about 30kHz! No 15kHz support. Set your computer to 30kHz (VGA rate).
The monitor must support a 31kHz horizontal scan rate! PGA/PGC compatible monitors should be OK.
The four XOR gates are inside a single 74HCT86 chip. Don't use the 74HC86
(without the "T"!). Don't use a 74LS86.
10k 1 +-----+ comp. sync or
VGA pin 13, hsync >----+---------\/\/\-------| | /comp. sync
or /hsync | 2 | XOR |---+---+
\ +----\/\/\-------| | 3 | |
470 ohms / | 10k +-----+ | |
\ | | \
| | | / 10k
GND | +-----+ 4 | \
| 6 | |---+ |
VGA pin 14, vsync >---------+ +-----------| XOR | |
or /vsync | | | |---+---+
\ | +-----+ 5 | |
470 ohms / | comp. + | \
\ | sync --- / 10k
| | 10uF --- \
GND | (any type) | |
| GND GND
|
| 12 +-----+
+--------------| | 11 /comp. sync
| 13 | XOR |----+------------+
| To +---| | | |
| 74HCT86 | +-----+ | |
| pin >--+ | |
| 14 | 9 +-----+ | |
| (+5V) +---| | 8 | /comp.|
| 10 | XOR |----+ sync |
+--------------| | __/--+ |
+-----+ __/ | |
| 5 | |
+-----9 | |
| | 4---+
+-----8 |
VGA pin 3, blue >-------------------------------------------|---------3 |
+-----7 |
VGA pin 2, green >-------------------------------------------|---------2 |
+-----6 |
VGA pin 1, red >-------------------------------------------|---------1 |
| \__ |
| \--+
|
|\| GND 9 pin D-sub
VGA pin 9, +5V >----| |----+ male (rear
|/| | view, solder
| side) To
|\| | monitor
USB power +5V >----| |----+---------> 74HCT86 pin 14 (+5V)
|/| |
---
--- 0.1uF ceramic
|
USB power GND >-----------+---------> 74HCT86 pin 7 (GND)
|
|
VGA pins 5-8, ground >-------+
|
VGA pin 10, ground >-------+
Some VGA devices will output +5V. Some don't. Some VGA cables lack that pin.
If you get no signal or no sync, then connect the USB power. Or you could use
PS/2 or AT keyboard power.
It matters which way round you put the diodes:
End with stripe
|
|\| V
----| |----
|/|
If using an electrolytic 10uF capacitor:
Stripe indicates negative
|
V
___________
/ \========\----
\__/________/---- <-- +
Tantalums are different, their + leg is marked +
Pin numbers for 74HCT86 chip:
Top view of chip, legs down (pointing away from you):
+--- Pin 1 identified by dot in corner, and notch at top of chip
| |
V V
+-- --+
1 -|* U |- 14
2 -| |- 13
3 -| |- 12
4 -| |- 11
5 -| |- 10
6 -| |- 9
7 -| |- 8
+------
9 pin monitor:
Standard CGA Type-3 Early IBM VGA
(type-2) (type-1) (Taxan/PGA/PGC) 9 pin (type-4)
------------------------------------------------------------------------------
1 Ground Ground Red Red
2 Ground or N/C Ground or N/C Green Green
3 Red Red (TTL) Blue Blue
4 Green Green (TTL) Comp. sync (TTL) Horiz. sync (TTL)
5 Blue Blue (TTL) Vert. size select Vert. sync (TTL)
6 Do not connect! Intensity (TTL) Ground Ground
7 Comp. sync (TTL*) ++ - Ground Ground
8 Horiz. sync (TTL) Horiz. sync (TTL) Ground Ground
9 Vert. sync (TTL) Vert. sync (TTL) Ground Ground
R, G, B signals are 0.7Vp-p terminated in 75 ohms unless TTL.
* Some monitors can accept 0.3Vp-p sync. Impedance can be 75 ohms up to a
few k.
++ Some monitors tie composite sync and horizontal sync pins internally!
Do not provide both composite and H/V sync at the same time.
Most analogue RGB monitors will accept either active-low or active-high for H
and V sync. As long as they're the same polarity. Most want active-low for
composite sync.
CGA monitors are weird and want active-high.
You should not apply composite sync to the horizontal sync input while at the
same time applying vertical sync to the vertical sync input. Either apply
clean horizontal sync, or composite sync only. Some will accept composite sync
via the vertical pin. Some via the horizontal pin.
The function of pin 6 on type-2 monitors varies! Don't connect it.
SCART TV (input), relevant pins:
--------------------------------
2 Audio in right
4 Audio ground
5 Video ground
6 Audio in left
7 Blue in (0.7Vp-p, 75 ohms)
8 AV channel select switching input (5-12V to switch to AV mode)
9 Video ground
11 Green in (0.7Vp-p, 75 ohms)
13 Video ground
15 Red in (0.7Vp-p, 75 ohms)
16 RGB select (1-3V to select RGB mode, 75 ohms)
17 Video ground
18 Video ground
20 Composite video (1Vp-p) or active-low sync (0.3Vp-p, 75 ohms) in
21* Chassis ground
* Connector shield/shroud
Most SCART inputs have AC-coupled R, G, B, video/sync lines. Some are DC-
coupled in which case it's a good idea to put capacitors in series.