RAD2X - No picture with either AES or NGCD

edd_jedi

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I have been using a RAD2X with my Mega Drive 2 & Mega CD 2for a while, so thought I would pick up the adapter to use it with my Neo Geo consoles too. However the adapter arrived this weekend, and with the AES I get the colour bars, and on the NGCD I get no picture at all, just a black screen. I do get audio with both consoles though. Anyone else experienced this?

The third photo shows the RAD2X working with my Mega CD, just to show it works.

IMG_2547.jpeg IMG_2546.jpeg IMG_2548.jpeg
 

GohanX

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Try plugging in the USB port of the RAD2x into a power source and see if it works. Color bars is a sign that it’s not getting enough power, maybe the 5v line on the Neos just aren’t strong enough. It really shouldn’t need it, but it’s worth a shot.
 

edd_jedi

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In case anyone else runs into this issue, it turned out to be my TV (Panasonic.) I was getting the same behaviour with an OSSC, however that has a 'Panasonic hack' setting which fixes it. Although I'm not sure why it only affects my Neo Geo consoles (as per the first post, my MD works fine.)
 

ggallegos1

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Neo Geo has weird sync rates and power requirements, it's not uncommon for them to be a bit finicky
 

Neo Alec

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It only affects the Neo Geo because of its non-standard sync rate.
 

Xian Xi

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Could also be sync voltage, probably out of the 250mv-900mv range.

Try using luma as sync on the NGCD. There should be a tutorial floating round.
 

maki

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NeoGeo CD Top Loader have no CSYNC output on the AV port, it shorted with composite video instead, some later AES have that as well.

Additionally, the NeoGeoCD (and MV1F) have this weirdness about their CSYNC:

My OSSC would not display a picture with NGCD, unless they had the CSYNC restored and then the timing fixes applied for the OSSC.
I don't own a RAD2X, so I don't know what fixes it there, maybe updating the firmware?

Attached a picture of how I restored CSYNC.

Edit:
This is syncing via Chroma.. somehow OSSC manages to do that better than on Composite Video
So don't do this, this is WRONG
 

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edd_jedi

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My NGCD works on the OSSC with the Panasonic Hack turned on, so maybe that might fix it for other TV brands too?
 

maki

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My NGCD works on the OSSC with the Panasonic Hack turned on, so maybe that might fix it for other TV brands too?
My OSSC couldn't sync to the signal, my Monitor (Dell C5519Q) is fine even with passthrough if the refresh rate is close enough to 60Hz.
 

edd_jedi

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Interesting, the NGCD works just fine with the Rad2x on my living room TV (TCL) maybe I just got lucky with that one.
 

Neo Alec

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Don't do the NGCD CSYNC mod; it doesn't work right. I confirmed on a toploader and CDZ. I ended up changing both to sync on luma. Here's the issue:

 

maki

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So I checked, and I really thought I used CSYNC OUT on the CXA1645, but it doesn't have a CSYNC out .. I mixed that up with the CXA1145.
I actually used Chroma to sync :D
Somehow the OSSC managed ot make it work, but that not supposed to be like that.

So, next try.
I could use a THS7374 as amp and a few passives to get a 75Ohm signal.
Or I can use a EL1883 sync stripper, this one is much faster than the LM1881.
I had one of these around and a tiny PCB for it that I always looked for an excuse to use:


IMG_0024.JPG

IMG_0023.JPG

Isolating the CSYNC Pin on the PCB:
PXL_20230102_180423284.jpg

Quick&Dirty test setup:
Taking the TTL CSYNC from the Pin 10 of the CXA1645 as input, on the CSYNC output from the EL1883 there is a 470 Ohm resistor in series and then a 75 Ohm resistor against ground, this yield around 0.6V CSYNC which is fine for 75Ohm consumers, it you want 5V TTL, leave both resistors out.
By using TTL CYNC as input, I avoid delay caused by the mixer that creates Composite Video, also the ES1883 is faster than a LM1881 and won't cause delay/shifted picture.
PXL_20230102_190001174.jpg

PXL_20230102_190103219.jpg

It does not change that the OSSC needs the timings adjusted or it won't sync to it.

Edit:
it can be done with two resistors and a cap
from the CXA pin 10: a 10k resistor in series to a 470uF cap (negative leg to the AV port) and a 1.8k Ohm pull down results in 0.6V CSYNC
using lower value serial resistor will reduce the actual TTL CSYNC Vpp, not recommended

PXL_20230106_174121336.jpg
 
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edd_jedi

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Well this was a pleasant surprise, the AES works on my Amiga monitor with the OSSC in passthrough mode :)

IMG_2663.jpeg
 
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