Panasonic FS-A1 Mk II - no video signal

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By sabre470

Resident (35)

sabre470's picture

17-10-2017, 01:51

Hey Guys,

Apologies in advance for reviving an old thread.

I've been enjoying my MSX2 machine for a while in composite, I decided to give RGB a try and I built an RGB cable using the pin-out provided in this page: https://www.faq.msxnet.org/connector.html

Quote:

RGB connector (Japanese models)

(Giovanni R. Nunes, Fabio Ricardo Schmidlin)
This is the standard MSX RGB pinout according to the MSX-Datapack.

DIN 8 pins female

1 GND
2 Audio
3 AV (*1)
4 C SYNC (*2)
5 YS (*3)
6 R
7 G
8 B

7 6
3 8 1
5 4
2
(View from plug - male)
Notes:
*1: Composite Video (aka CVBS). May be NC, or fixed to 1.8V via pull-up resistor in some models
*2: Composite sync. The signal level is 1.8Vpp (composite video standard). May be mixed either with Luma or Composite video itself (Panasonic machines). This means that it has to be passed through a sync cleaner and level adjuster to be able to be used in monitors that expect a TTL signal
*3: +3V~+5V signal, used to switch the TV to the RGB input. Also allows superimposing on SCART and RGB21 TVs if the MSX has such hardware built-in. Shouldn't be used as Vcc

Unfortunately, I'm not getting image in RGB, I get the sound all right. I tried a few different cables apart from the one I built and I get the same result.

Now looking at the datasheet of the cxa1145, I'm coming to the conclusion that since I have composite signal loud and clear, RGB signal gets into the chip all right. But for some reasons, what's coming out of the chip (if anything) in terms of RGB doesn't get to the screen. I've double and triple checked my cable so I'm quite confident it is working, I even built a 2nd one just to be sure.

Any thoughts on what the problem could be?

Many thanks for the help in advance :)

By Alexey

Guardian (3121)

Alexey's picture

17-10-2017, 12:31

If you get a composite signal, then RGB should be working fine. The problem may be not in the cable, but in your monitor/TV. Some of them don't like composite sync, so it needs to be splitted. I think the easiest way for you would be buying/building a SCART cable and connect your computer (what brand/model btw?) to a SCART on your TV.

BTW, you need to be careful when building such cables. Certain computers output 12v on one of the RGB out pins for switching monitors/TVs into a different mode. So if you send those 12v where they don't belong, you may damage the monitor/TV's internals.

By sabre470

Resident (35)

sabre470's picture

17-10-2017, 16:23

Hi Alexey, many thanks for your answer, the MSX model is an FS-A1 Mark II, the same one that was the subject of the repair in this thread with the faulty hybrid board.

Currently I'm connecting the MSX to an XRGB Mini Framemeister, the RGB scart goes in a scart to framemeister adapter that has a built-in sync stripper (LM1881 chip).

I also tried a scart to framemeister adapter without sync stripper and the result is the same

The framemeister is connected to an LCD TV, that TV doesn't have any scart connector.

I've tested both scart to framemeister adapter(s) with other machines and they seem to work fine.

So I'm a bit lost as to why I don't get any image with the MSX? Perhaps I need to add a resistor between pin 8 and 16 to feed the sync stripper although I'm not sure if the MSX would like it. In any case I would assume the framemeister would get at least some form of image with either adapter but I only get sound nothing else.

By sabre470

Resident (35)

sabre470's picture

29-11-2017, 18:07

Hey Folks,

A quick update on my MSX2, I finally caved in and bought another machine... Same one with a floppy drive an FS-A1F. It works like a charm in RGB, floppy drive working like a treat too. Reasonably priced, so now spending time playing in good conditions at last.

Thank you for all the input and help. I'll keep FS-A1 MkII as spare and for parts if needed. I may give it another RGB output using this guide: http://msx.hansotten.com/uploads/files/svirgb.pdf and bypass the daughter board, will see...

By gdx

Enlighted (4498)

gdx's picture

29-11-2017, 23:23

I think the Panasonic FS-A1mkII works fine with the framemeister.

Alexey wrote:

If you get a composite signal, then RGB should be working fine.

No, MSX2 FS-A1 series use a separate board for the RGB signal. Capacitors of this board age badly and the chip often break down after several years. This was the case for my FS-A1.

Maybe the Panasonic FS-A1 schematic can help you.
http://www.geocities.jp/atx197/FS-A1_PWB-REV02_schematic_REV...

This model is close to yours.

sabre470 wrote:

Apologies in advance for reviving an old thread.

Why? Threads are not meant to be entered. It's a good thing to continue a topic started.

By amigo-mexicano

Supporter (4)

amigo-mexicano's picture

23-06-2021, 18:40

Hello everyone!

I have this A1mkII with a similar video problem, the issue is indeed, the small green board. In my case a component fell off! I can't quite read what it says, so I was wondering if someone knows what replacement should I buy. It seems it says "FR" or "PR".

Thanks in advance!

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