Retro Scaler A1

[brandon.arnold]

It depends on your output impedance, which I presume is unknown. A device that re-amplifies and gives the output signal a fixed impedance of 75-ohm makes it simpler (like the HAS, or the tri-sync helper/Jammafier).

The 75-ohm setting is for devices with an output impedance of 75-ohm, and this terminates the signal with 75-ohm. If you measure the signal unterminated at 1.4, the termination in the A1 will bring it down to 0.7V.

The arcade setting has a termination of 1K. Arcade boards have wildly different impedances and there is no standard - but arcade monitors often terminate the signal with 1K. The arcade setting also has a voltage divider in the mix, to bring the levels down to something that will not overload the ADC chip.

If you feed the scaler a 1.4V signal with high impedance - there is no right setting, as the 75-ohm termination will make it dim, and the arcade setting expects a higher voltage.

There is also a component of the A1 that comes into play, which is the analog gain stage. This accepts 0.5 to 1.0V, and will adjust it to make full use of the 10bit ADC. This is adjusted every time sync stabilizes, if something clips, and a few seconds after sync stabilizes. You can also trigger a manual re-adjustment by pressing the middle button on the A1.

In practice, this works pretty well for 75-ohm sources, and raw jamma sources.

Thanks for sharing all that, because it's interesting. That said, I don't think the output impedance is actually unknown here. It's 75 ohms. I put a 75 ohm termination (well, 68 ohms) in the circuit that my oscilloscope probe is going in (after I took the video) and adjusted the supergun potentiometer so that it read 700 mV VMax. When I remove the resistor, it reads 1.4V Vmax. That's what I was trying to say in the comment to which you replying.

 

[invzim]

If it's un-amplified, I think your results will be different across different boards. I have a macross PCB that measures over 6V unterminated, while a Mr.Driller G measures 3V (but with an insane impedance of less than 10ohm).

If you start the A1 with an sd-card (not ex-fat), you will get an .ini file on it - you can change the setting for console to enable and power the A1 with a computer, you will get a USB serial console device which will log things real-time (and you can then see when it clips, re-adjusts etc).

 

[brandon.arnold]

If it's un-amplified, I think your results will be different across different boards. I have a macross PCB that measures over 6V unterminated, while a Mr.Driller G measures 3V (but with an insane impedance of less than 10ohm).

If you start the A1 with an sd-card (not ex-fat), you will get an .ini file on it - you can change the setting for console to enable and power the A1 with a computer, you will get a USB serial console device which will log things real-time (and you can then see when it clips, re-adjusts etc).

Ah, makes sense. Great to know. And I will have to open up the A1 console soon to study the output!

 

[Ma-Yuan]

I got my retro scaler a1 yesterday and use it in my Naomi Universal Cabinet with a 31khz Sanwa Monitor. Unfortunately i have an issue with it. After a while can be 20 seconds or a few minutes it seems the sync drops out for about 250 to 500 ms. The scaler is connected to a jammafier that runs a single slot MVS. The cheap china scaler i used before did not have this issue.

I hope you can help me out

Edit: I did a bit more testing on a PC LCD monitor same issue. The screen just fades to black here but the effect is much longer then on my naomi crt

 

[invzim]

Is the jammafier a rev 2.0 - and if so, is it set to JAMMA video (default is tri-sync)? Try that first if you haven't. Do you have other games you can try with?

 

[Ma-Yuan]

Is the jammafier a rev 2.0 - and if so, is it set to JAMMA video (default is tri-sync)? Try that first if you haven't. Do you have other games you can try with?

Thx for the quick answer. I have Regen C and Seperate HC it is always set to Regen C so far. So I will try Seperate HC now.

 

[invzim]

Thx for the quick answer. I have Regen C and Seperate HC it is always set to Regen C so far. So I will try Seperate HC now.

Not quite - there is a physical switch on the Jammafier you need to toggle. This will output RGB and sync completely raw, which is what the A1 expects unless you change settings on it.

 

[Ma-Yuan]

After i set it to separate HC the issue was gone nothing for at least 20 minutes. So i am confused now can i damage anything with this?

The config is set to tll for sync and arcade for rgb.

 

[invzim]

For best results, set the jammafier to to 'JAMMA' with the physical switch (there should then be no sync options on the OLED), and use the A1 with default config (no sd card).

 

[Ma-Yuan]

Can i at least a config it for scanlines? I don't want open my cabinet each time i play. And if i have no issues right now is it save to leave it like this?

 

[invzim]

Just trying to make sure you got the correct configuration

 

[Ma-Yuan]

Just trying to make sure you got the correct configuration

I appreciate that a lot so i assume if no further hick ups appear i leave ot like this if it shows up again i will switch to jamma.

 

[invzim]

I appreciate that a lot so i assume if no further hick ups appear i leave ot like this if it shows up again i will switch to jamma.

No, if the Jammafier is in tri-sync mode, rgb should be set to 75-ohm. As I've said, the recommended configuration is to flip the physical switch on the Jammafier to JAMMA - and use default config on the A1 (rgb=arcade, sync=ttl). When the a1 is in (default) arcade mode, it expects a higher voltage meaning the image may be dark if you feed it VGA level signals.

 

[Ma-Yuan]

Ok i will flip the switch but I did not consider the picture dark.

 

[Ma-Yuan]

Ok you were right its a bit brighter.

Thx again you made a great product love having visible scanlines on my Naomi

 

[JohnRambo'sKnife]

@invzim - For pin 9 power to the Tri-sync helper, I assume power only stays at input pin 9 and does not follow through to pin 9 on the output connector to the monitor?

 

[Ma-Yuan]

I have an issue again i have Tekken 3 PCB and if i use the VGA connection with the scaler i get moving picture if i use the jamma connection and the jammafier i get dark and more or less stable picture but then i cant use the jvs usb connection. Any idea whats wrong?

 

[Ma-Yuan]

I tested my cheap 20 euro china scaler. It has no issues what so ever.

 

[RGB]

Tekken 3 can display in progressive or interlaced, have you tried to change it?

 

[Ma-Yuan]

I found a sync option that worked. Set it to separate. But i have not found the 240p vs 480i setting yet. It runs currently in 480i and that looks horrible.