GFX9000 on Sony KX-14CP1

Ascended (18719)

04-12-2020, 15:05

I always had a problem to get proper sync on my Sony KX-14CP1 when connecting my GFX9000. (Video works fine with the RGB out of my turboR.) So, with a friend I added a 220 ohm resistor in on the sync line (pin 20, in series), and that fixed the sync.

But a weird problem remains.
Part of the time, the picture is 100% perfect.
Another (unfortunately larger) part of the time, the image is way too dark and weird, with flickering stuff.

I have no idea how to switch between the two situations.

My friend thinks it may be caused by the voltages of the RGB lines. But why would it only happen part of the time?
Anyone got an idea?

By Pencioner

Scribe (1518)

04-12-2020, 16:41

i think i have seen someone asking this in another thread some time ago... but i don't remember the details

By Mumbly

Expert (88)

04-12-2020, 17:28

hmmm, I don't have the issue (I have the technobyte v2 version), and there are no resistor on the RGBs line.
For certain console there are putting indeed a resistor on RGB, since there are no 75 ohms termination on certain monitors/tv.

But when I have fixed the sync problem for Metalion, I remember that I had similar issue with lower or higher value of resistor with a range of 100 ohms, so maybe the impedance of your display is different than another KX 14-cp1 display.
At least 220 ohms worked for 2 KX-14 CP1.

By hamlet

Scribe (4096)

04-12-2020, 18:16

technobytes' Powergraph /Light and GFXnine works great with KX-14CP1, only the original GFX9000 gives problems as Manuel told.

By KdL

Paragon (1429)

04-12-2020, 19:39

I had solved a similar issue in the past by connecting the GFX9000 V1.1 to an external power supply. To do this I had isolated the +5V pins of the GFX9000 board using a slot expander. At the time I was using a PC cabinet for this slot expander and had used a +5V line from a high quality Seasonic power supply. My Sunrise GFX9000 has always been very sensitive to low quality or worn out power supplies, but video synchronization was disturbed even when the floppy disk engine was in use.

By Manuel

Ascended (18719)

04-12-2020, 22:58

Mumbly: the 220ohs works great to fix the sync issue. That is completely solved. Without that resistor, I only had a rolling flashing screen, nothing usable. With it, I have what I wrote: either perfect image or a weird dark image. I have only seen it change after starting up. Perhaps it's power supply related indeed. But my turboR has a 220V power supply, but may it isn't the best.
I'll do more tests with a Philips monitor.

By Mumbly

Expert (88)

04-12-2020, 23:42

Ok, based on what Kdl and Hamlet has written, I must admit I have a slot expander with an external power supply and a technobyte version, I missed those aspects, sorry

@Kdl: great idea
If it's related to the power supply, Perhaps you can test with another machine than your turbo R or with a slot expander with an external power supply like the technobyte ones, indeed.

I've also experienced than if the voltage on pin 16 is too high or too low, you have weird effects on KX14 CP1 monitors, that's why I put a 180 Ohms resistors there if it's too high, or an external battery/power supply directly connected on that pin if the signal is too low.

Parasites can be also filtered on R G B lines by putting a capacitor of 200µfd with the + polarity MSX side.
In a normal way of working, for the MSXs I have tested (Philips, Panasonic and Sony) it's not mandatory, now
those weren't enhanced in any way.

By Manuel

Ascended (18719)

05-12-2020, 00:13

Pin 16 is the blanking signal... perhaps that voltage is floating a bit indeed. What kind of effects did you see?

Also, does somone have a PDF of the service manual or user manual of the KX-14CP1?

By KdL

Paragon (1429)

05-12-2020, 01:51

Sunrise GFX9000 V1.1 has a dark image when the +5V is not reached at 100%.

For example:
1chipMSX offers +5.2V while SX-1 offers +4.8V.
On 1chipMSX the image is very clear while on SX-1 it is very dark.

By KdL

Paragon (1429)

05-12-2020, 02:15

Sorry I wanted to write ...
On 1chipMSX the image is perfectly sharp, perhaps slightly lightened, while on SX-1 it is very dark.

In my opinion, a correct voltage for the Sunrise GFX9000 should stay in the range of +5V to +5.25V max.
The voltage I am talking about is not that of the cable but that present on the MSX slot when the cartridge is inserted.

By Mumbly

Expert (88)

05-12-2020, 02:01

It could be that, as it is a DC output, it's quite easy to measure, if the voltage is too high (but I have doubts on it), you put a resistor on pin 16 like the schemas here.