jef@lbl-rtsg.arpa (12/25/85)
From: jef@lbl-rtsg.arpa
This message should be the definitive word on how to hook up a Sony analog
RGB monitor, such as the KV20XBR or KV25XBR (and probably the KV1311), to
your Amiga. The previous two postings on this subject were incomplete.
They were a big help in making our cable, but we were not able to actually
get the cable to work without consulting both the Amiga hardware manual and
the service manual for the Sony. Hopefully, this message will help people
avoid such hassles in the future.
First, the D connector. The Amiga puts its RGB signals out to a 23-pin D
connector. As the previous posters have noted, 23-pin D's are very hard to
find. Instead, get a 25-pin female D (should cost about $5) and wield a
file. Be careful to preserve the structural integrity of the connector.
(Get two and experiment on the first). WARNING: this surgery changes the
pin numbering. If you cut off the side with pins 13 and 25, pins 1 - 12
will still be correct but the pins labeled 14 - 24 on your connector will
now be 13 - 23.
The complete pinout for the Amiga (looking at the business end of your
female connector):
---
| \
xclk | 1 \
| 13 | gndrtn
xclken | 2 |
| 14 | ZD
red | 3 |
| 15 | C1
green | 4 |
| 16 | gnd
blue | 5 |
| 17 | gnd
DI | 6 |
| 18 | gnd
DB | 7 |
| 19 | gnd
DG | 8 |
| 20 | gnd
DR | 9 |
| 21 | -5 volt power
CSYNC | 10 |
| 22 | +12 volt power
HSYNC | 11 |
| 23 | +5 volt power
VSYNC | 12 /
| /
---
The Amiga manual does not specify which of the grounds should be associated
with which of the signals, but it probably does not matter. The Amiga does
not send any audio signals through its RGB connector, so you have to get the
sound from the regular RCA connectors.
On the Sony side, the connector is a rectangular 34 pin (17 x 2) guy with
tenth inch spacing. Sony calls it a "PX-34" and wants $19 for it. Since
that was blatantly ridiculous, we looked around and found a 44-pin version
for sale at Dick Smith's. If you do this, you can benefit from our
experience: for our first attempt we cut it down to 34 pins, and found that
although it worked, it could be mis-inserted by one pin in either direction.
To avoid this, only cut the connector down to 38 pins (19 x 2), and use the
middle 34. This will probably be a tight fit - you may have to file it
down a bit more.
Note that the 34-pin socket is keyed, and presumably Sony's PX-34 is too.
The improvised connector is not, so it can be inserted upside-down. You
can fix this by super-glueing a small piece of plastic to the left side of the
connector. You'll have to examine the socket to see exactly how to do this.
However, a simpler solution is to just mark the left side somehow. Craig
used a drop of Liquid Paper.
The pinout for the Sony (looking at the socket on the back of the Sony):
--------
audio select | 34 17 |
RGB/normal mode select | 33 16 | ground
| 32 15 | ground
vertical sync | 31 14 |
horizontal or composite sync | 30 13 | ground
blanking input | 29 12 | ground
| 28 11 | ground
blue input | 27 10 | ground
green input | 26 9 | ground
red input | 25 8 | ground
left audio input | 24 7 | left audio input ground
composite video input | 23 6 | composite video output ground
| 22 5 | remote control ground
mode select | 21 4 | ground
right audio input | 20 3 | right audio input ground
| 19 2 | +5 volt power
| 18 1 | +5 volt power
--------
According to the schematic, the grounds are all connected together inside
the Sony, so you could ground any signal with any ground. For convenience
we grounded each signal with the ground opposite it. The audio select line
is a TTL input - ground or +5 volts - that tells the Sony whether to take
audio input from the cable or not. You want this line tied high, so get a
4.7K ohm 1/4 watt pull-up resistor and use it like a jumper right on the
back of the connector, between audio select and the pin 2 power supply.
Be sure to insulate the resistor's leads! Use heat shrink, or some
insulation removed from some similarly-sized wire.
For the actual wires, multi-conductor works ok for short distances - that's
what our first version used. But the purist will want 75-ohm coax. Dick
Smith's sold us some good quality coax for $0.16 per foot. You will need
six lines (R, G, B, sync, left, and right), so for a five-foot cable you
need 30 feet, or about $5 worth.
Now here's one more diagram showing what connects to what:
Amiga Sony
CSYNC 10 ----------------------------- 30 horizontal or composite sync
blue 5 ----------------------------- 27 blue input
green 4 ----------------------------- 26 green input
red 3 ----------------------------- 25 red input
left RCA plug ----------------------------- 24 left audio input
right RCA plug ----------------------------- 20 right audio input
/--4.7K-- 34 audio select
\-------- 2 +5 volt power
In addition, connect as many grounds as is convenient. If you're using coax,
you might as well connect all six grounds on both sides. If you're using a
multi-conductor wire, there might not be enough conductors for that, so just
connect as many grounds as you have conductors.
Oh yeah, I almost forgot to mention the two male RCA plugs you will need.
It's ok to use coax for these lines, even though they are only audio signals.
If you can find both red and black plugs, use red for the right channel.
Finally, is it worth it? Absolutely, positively, yes. The difference in
image quality between composite video and RGB is breathtaking. No more
smeared colors, no ghostly vertical lines in the background, very little
blooming when the brightness of the picture changes rapidly, just nice sharp
rectangular pixels exactly where you place them. If you bought one of the
Sony monitors but then held off on making the cable when you found out how
hard it is, hold off no longer!
And if you still don't feel confident enough to make the cable yourself,
don't worry too much. You'll probably be able to buy one fairly soon.
(Start saving up now, it won't be cheap.)
Happy hacking.
-------------
Jef and Craig