On 30/01/12 13:43, Jules Richardson wrote:
Are you absolutely sure it's not a mechanical
fault - broken cable,
broken/intermittent socket pin (CRT or computer side), damaged solder
joints around the socket inside the CRT etc.? It may be that the
monitor's default state results in it almost locking onto the picture,
even when it's not seeing any sync signal.
Two for two, Jules... Damaged connector on the monitor side of the
cable, *AND* a broken wire inside the cable (monitor side again). This
thing's been slammed against a wall at some point in its life. Hardly
surprising seeing as it's an ex-school machine.
The broken wire half-killed one of the colour channels, turning the
picture magenta. The broken pin killed the sync, but only some of the
time. Reseating the cable got the sync to work (ish), but wiggling it
made the colour flicker between "OK" and "someone's been playing with
the RGB gain".
Said cable has now been replaced with a homebrew cable made from a
couple of DE9 connectors and shells and some 6-core screened cable.
Little hint for anyone thinking of using the pinouts in the A3000
Service Manual and Acorn Application Note 249 to make a cable. The
diagram on AN249 page 4 has the pins mirrored. Assuming you're using the
pin numbers on the back of the DE9 socket, the pinout for the AKF17 is:
1. Blue
2. Green
3. Red
4. n/c
5. GND
6. n/c
7. n/c
8. Composite sync
9. n/c
Connector on the monitor is a DE9 plug (male), so you want a socket
(female connector) to make a cable.
The A3000 also uses a DE9 but of the opposite gender. Pinout is:
1. Red
2. Green
3. Blue
4. HSync or CSync
If LK24 is set 2-3, you get CSYNC. If it's set 1-2, you get HSYNC.
5. VSync or Mode
If LK25 is fitted, you get VSync. If not, you get MODE (required for
SCART cables)
6, 7, 8, 9: All GND
To get the machine to talk to the AKF17 --
Hold numpad 0. Power on.
F12
*Configure Sync Auto
*Configure MonitorType 0
Enter
Hit the RESET button.
Enjoy!
Jobs for later: new power switch on the monitor, find or buy an Acorn
mouse, seeing as the PS2MouseMini adapter won't fit in the socket on an
A3000... :(
Other than that? The AKF17 flickers like there's no tomorrow, but that's
to be expected for a TV-rate monitor being run in single-field
non-interlaced mode (special thanks to Acorn for that bright idea). It's
much nicer when fed from a video generator...
Although it does one-up the Cub on one point: the monitor stand isn't
broken :)
By default it tilts up at a ~20 degree angle (I guess the assumption was
that it'd be used on a table at slightly below eye level). There's a
two-piece plastic tilt-bail on the base which allows the angle to be
reduced by half, or reduced to around zero. I have it set in the latter
mode :)
Now I just need a box of adapters for it. JAMMA, CVBS (hmm, I'll need a
colour decoder for that), ..... hmm, what else can I adapt to RGB+CSYNC
at TV rate? :)
Cheers,
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/