GBS 8220 loosing signal every 18 seconds !

Resident (37)

15-08-2019, 17:53

Hi Guys
Take a look at this video:
https://www.youtube.com/watch?v=0J_cIum0P6Q

This is my Panasonic FS-A1WX connected via RGB to a GBS8220 - version 3.
For some reason, the image goes "no signal" every 18 seconds and then go back normal again.
This repeats forever. (without any human interaction).

Have you guys seen something like that before?
* I tried to use another power supply, with the same results.
* I tried to "reset" the board. (pressing down for 5 seconds), with the same results.

Well, I don't know if the board has a problem or this is the MSX.
But it really doesn't make sense.

Por Pentarou

Hero (562)

15-08-2019, 18:35

A few versions of these boards need fixes for power, some versions also require beefy PSU.
These boards are meant to be used with arcade PCBs, they are quite picky about the signals and the original software has a lot of limitations.
Spend a couple dollars for an ESP8266 board and use GBS Control

Por glufke

Resident (37)

15-08-2019, 19:21

I tried with 2 power supplies:
* One regular USB phone charger. (5V 2A).
* I have an USB HUB --> Anker 10-Port 60W USB 3.0 Hub with 7 Data Transfer Ports and 3 PowerIQ

Both with same results.
I don't know if I should try with a 3A or 4A power supply...
I've heard that this board may have "no signal" when it's too hot. (but this is not the case).
It's just weird that it's exactly every 18 seconds. It doesn't make sense.

Por Pentarou

Hero (562)

15-08-2019, 19:30

I thing 1A @ 5V should be enough, but I wouldn't trust USB phone chargers.
You should also describe how you connected the MSX to the board, especially how you are providing the sync signal to it.

Por glufke

Resident (37)

15-08-2019, 20:18

I am following this diagram:
https://www.msx.org/wiki/RGB_(8-pin_DIN_45326)

Pin.......Description..............GBS......................
1.........GND Ground.............Black Wire
4.........CSYNC....................GRAY (this is the horizonal sync)
6.........R Red signal............RED wire
7.........G Green signal.........GREEN wire
8.........B Blue signal............BLUE wire

The board has also a YELLOW wire (Vertical SYNC). This is not being used.

I found this video: https://www.youtube.com/watch?v=Tl6AFolVO4U
This guy used the board in the TurboR without any mod, and using the above pinout. (it's written in the comments):
Hello. These are the proper connections: black (gnd)->turboR rgb pin 1, red->turboR rgb pin 6, green->turboR rgb pin 7, blue->turboR rgb pin 8, gray (sync)->turboR rgb pin 4, yellow (vert. sync) -> not connected. Hope it helps. All the best.

Por Pentarou

Hero (562)

15-08-2019, 20:45

Well, if you had the GBS Control you could use the debug output to troubleshoot the problem
IMHO it's not a PSU problem but a sync compatibility problem, and since there are many different versions of these board it could be that some are more tolerant than others.
Maybe this fix could help:

Quote:

Sync (no extra sync stripper)

Every GBS board comes with ~500 Ohm termination on the sync input.
This termination is meant for VGA and most arcade boards. It is unfit for most other sources however.
If you want to use the RGBS input for regular TV level sources (game consoles), the GBS requires one additional 100 Ohm resistor to ground on the sync input.
Together with the factory resistor of ~500 Ohm, this will bring the total termination close to TV levels of 75 Ohm.
Info: The total resistance is closer to 82 Ohm with this extra resistor. This is intentional, as it leaves more headroom.

Por glufke

Resident (37)

15-08-2019, 21:00

I will try that tonight...(and some other things).
I'll keep this topic updated about this problem.

Por ~mk~

Champion (340)

16-08-2019, 17:53

I have the same issue.
It's been a long time since I tried but I think the issue happens with 60hz video only.
Try with the command VDP(10)=2 and see if it changes anything.
Also try switching to interlaced video with SCREEN,,,,,1.
One of those two things "solved" the problem for me.
Not real solution but might help troubleshoot the problem.

Por alex3331

Supporter (9)

03-08-2022, 19:39

is VDP(10) = 2 a BASIC command?

Por tfh

Prophet (3429)

03-08-2022, 19:58

Yes... that is a BASIC command.

Por alex3331

Supporter (9)

04-08-2022, 15:37

VDP(10)=2 does not help. I already removed (and shorted) the potentiometers from GBX8220 board and installed 100 ohm resistor to bring sync impedance to 75 ohm as advised. No change. Probably need GBS control.
I have 2 boards - 8200 (black buttons) and 8220 (yellow buttons) - both are bad with MSX and work fine with everything else I plug in.
Are there any other ways for RGBS on MSX? 15 kHz monitor, maybe?