Ultimarc PSX to Arcade Monitor Adaptor

[dabone]

Does anyone else have one of these?

I purchased one for my psx (psone) and it's basically running the guns full out.
I was wondering if anyone else had tested it on a original psx.

Andy had not tested it, so he won't say if my unit is bad or not.
(He's only tested on a ps2)


Later,
dabone

[Minwah]

I purchased one for my psx (psone) and it's basically running the guns full out.

Sorry but what on earth does this mean? 

[dabone]

All white screen (You can barely make out the video).

Hooked up to a scope the signal is only about 20-30mv on top of a 4.5 volt offset.


Later,
dabone

[Minwah]

All white screen (You can barely make out the video).

Hooked up to a scope the signal is only about 20-30mv on top of a 4.5 volt offset.

Are you using a video amp?  I was using one with the Xbox AV adaptor and had a similar problem.  Removed the amp and now it's perfect.

[dabone]

This is the psx adapter cable with built in video amp.

http://www.ultimarc.com/psx.html

Later,
dabone

[Minwah]

This is the psx adapter cable with built in video amp.

The Xbox AV adaptor I got has a small seperate circuit board which you plug the vga-type connector into (see it in the attached pic, from the page you linked to).

I know Andy knows what he is doing but I was surprised these adaptors come with a video amp.  Afterall, the ArcadeVGA doesn't have one afaik, and I guess a lot of monitors don't require it (my Hantarex Polo certainly doesn't).

I would ask Andy what he thinks the problem is, I'm sure he'll be able to sort it for you.

[dabone]

It ended up being a design difference between the original psx and the ps2.

That's a older pic, the new adapters have a non removable video amp.
(The lm1881n circuit and the amp are on 1 board)


The original psx has a dc offset on the rgb lines, the ps2 has caps on the line to filter the dc. I added caps to the rgb lines of the psx and it works great.


(And most older monitors require the amp, and yours should work with or without it.)


p.s..

Keep up the great work on Mamewah, it is very much appreciated.



Later,
dabone

[Minwah]

That's a older pic, the new adapters have a non removable video amp.
(The lm1881n circuit and the amp are on 1 board)

I wonder what people do who don't require the amp?  Is there an amp-less version?

The original psx has a dc offset on the rgb lines, the ps2 has caps on the line to filter the dc. I added caps to the rgb lines of the psx and it works great.

Glad you got it working

(And most older monitors require the amp, and yours should work with or without it.)

Well with the amp the picture was unbearably bright, you couldn't read things properly etc.  Without the amp it is sweet.

Keep up the great work on Mamewah, it is very much appreciated.

No problemo

[dabone]

The jpac version of the converter is minus the video amp.
(But with a db15hd connector)




Later,
dabone

[AndyWarne]

I think this capacitor issue only arises with the Ps1 not Ps 2. The PS2 has AC-coupled outputs, as I confirmed by taking one apart and checking, so it already has capacitors fitted. The problem with the video on the PS 1 must be a DC voltage difference between the AV adaptor and the ground of the PS.
Actually grounding is an issue with all these consoles since they only have 2-wire power cables so actually are not really grounded at all.
Andy

[dabone]

How could the psx and the video amp have a different gnd when you get you +5 and ground from the psx itself?

The psx must have done this as a design choice? because the reason I tried the 220uf caps is that all psx scart cables I've seen have them in the connector.

Taken from the BYOAC consoles page.

Since the AV out on the playstation doesn't contain sync, you can strip a composite sync signal from the composite video line using an LM1881 circuit.   Note: you need to add 220uf capacitors (preferably non-polarized) connected in each R/G/B line before the monitor inputs or the picture will be quite dark.  [If you are hacking from a SCART cable, just re-use the capacitors already inside the SCART connector end.]

Apparently sony was too cheap to include them in the original design and left it to the cable makers to correct them.



Also, did you ever think of adding a external power supply and a female scart connecter to this circuit?
That should be all it need make a scart to rgb converter right? (Or an I missing something?)

Later,
dabone

[elvis]

Also, did you ever think of adding a external power supply and a female scart connecter to this circuit?
That should be all it need make a scart to rgb converter right? (Or an I missing something?)

This is what I'm going to do to my JAMMA cab.  The LM1881N, caps, female SCART adaptor and DB15 connector come to a grand total of around AU$20 (US$15).  That will build me a generic SCART->JAMMA converter, and then from there it's just a matter of plugging in any of my consoles via a SCART cable (with the exception of my PAL SNES, which doesn't do RGB at all).