Connected a 470uf cap to the wrong pin on the CXA encoder of Front Loader.

[LordKirkis]

Hey folks I'm pretty new to electronics and repair and would really appreciate any help with my Neo Geo CD. What happened was during a modification/ csync restoration I connected a 470uf 25v caps negative leg to the video pin and its positive leg was connected with 2 wires, 1 wire led to a 10kohm resistor which leads to pin 10 of the video encoder chip and the other wire went to 1830ohm resistor to pin 12 of the video encoder chip. And thats the mistake there I suspect.. as pin 12 is not ground but the power supply of half of the ic's circuit. So my question to you is; could powering the console power on in this state have caused damage to the chip or surrounding components? The game console boots, runs games, but I am seeing interference that look like scrolling, white moire pattern across most of the screen... and I also see very faint black smearing on some of the graphics that goes to the right side. I checked the voltage of the IC and all seems fine except pin 7 which is reading 4.7v when the info below says its suppose to be 1.7. I checked some of the nearby resistors and measured with a multi meter in circuit and found that some were off tolerance by 900ohms. Should I be measuring off circuit, is there anywhere else I should look? Thank you and appreciate any help you can offer.

 

[Neo Alec]

It sounds very possible, but I can't confirm if you fried it or not. You restored it to how it was and now it's doing something it wasn't before? Double check and redo the work.

There's such a variety of console mods posted online these days. This might be an unfortunate lesson that sometimes, especially if you're inexperienced, it's better to just leave well enough alone.

I'm not trying to be a dick here, I mean I've been in the position myself before where I go to do some mod work and halfway through regret it and wish I hadn't bothered doing the project. CSYNC might be one of those things where it's better to leave well enough alone unless you need it.

 

[LordKirkis]

It sounds very possible, but I can't confirm if you fried it or not. You restored it to how it was and now it's doing something it wasn't before? Double check and redo the work.

There's such a variety of console mods posted online these days. This might be an unfortunate lesson that sometimes, especially if you're inexperienced, it's better to just leave well enough alone.

I'm not trying to be a dick here, I mean I've been in the position myself before where I go to do some mod work and halfway through regret it and wish I hadn't bothered doing the project. CSYNC might be one of those things where it's better to leave well enough alone unless you need it.

Its definitely a hard lesson as I was very happy with the console. I use an Extron for all my consoles so I did need it. Right now the signal is on Luma and the moire pattern strangely mostly went away. Now if I see it its barely visible, but I still see the black smears on moving characters and the brightness is 12 candelas less than what it was before. I know because I measured it with a spectrometer and had set the lumens to 70 nits, its like 58 now after the screw up. I will most likely need to send it for repairs to someone who can handle this sort of issue.

 

[Neo Alec]

Yes. I guess you already undid the mod to double-check?

Just for posterity in this thread, if you don't want to mod your console for CSYNC, you can always use an external sync stripper:

Sync Stripper

Sync Stripper This page links to different ways to make your own sync stripper, as well as ways to make your own. Please note: You do not need a sync stripper for SCART equipment, but some monitors and BNC switches might require them. Please only use one if you know for a fact you’ll need it:

www.retrorgb.com

 

[maki]

@LordKirkis
the CXA1645P is easy to find in case you've shot it

Pin 7 is NTSC/PAL switching

NPIN - Pin for switching between NTSC and PAL modes NTSC: VCC, PAL: GND

4.7V is fine IMO to set NTSC

I don't really get the problem, can you take a pic or video?

 

[maki]

okay I checked my notes, this won't work with a simple resistor network, needs a sync splitter to get CSYNC

 

[LordKirkis]

okay I checked my notes, this won't work with a simple resistor network, needs a sync splitter to get CSYNC

Thanks both of you… Ive since found out the dimming was due to the BVM calibration settings reseting due to old battery. That said the moire pattern on the Neo Geo does remain and I am thinking the CXA was affected due to my error. I have ordered a new CXA and will be carefully installing it. My friend suggested I look at some of the caps on the Av and also the ones on the power supply just to be sure! I hope after that I can restore the consoles condition and enjoy it as best as I can! That aside the same buddy of mine lent me his Sync Stripper so I will be trying that soon as well. Will an update then. Thanks for the heads up and for showing concern. Now If that doesnt work I will just retro tink rgb to component which is what I should have used from the start. For now wish me luck that I save this beautiful console.

 

[LordKirkis]

@LordKirkis
the CXA1645P is easy to find in case you've shot it

Pin 7 is NTSC/PAL switching

4.7V is fine IMO to set NTSC

I don't really get the problem, can you take a pic or video?

I will try.

 

[maki]

this will not work without a SyncSplitter or other means to get a better signal

my info is wrong about a resistor network being enough, I had a broken CSYNC line in my AV Cable, causing it to be coupled capacitavly, would work only with the OSSC, no CRT

the VDP can't drive a 75Ohm load and drive the TTL internally at the same time, voltage collapses on CSYNC

 

[Neo Alec]

this will not work without a SyncSplitter or other means to get a better signal

my info is wrong about a resistor network being enough, I had a broken CSYNC line in my AV Cable, causing it to be coupled capacitavly, would work only with the OSSC, no CRT

the VDP can't drive a 75Ohm load and drive the TTL internally at the same time, voltage collapses on CSYNC

What about this?

https://twitter.com/i/web/status/1682109931120467970

 

[LordKirkis]

The resistor network gave me csync signal directly to BVMD32 but not through extron crosspoint 450

 

[LordKirkis]

Mayb

What about this?

https://twitter.com/i/web/status/1682109931120467970

maybe similar network but through these points?

 

[LordKirkis]

Hey guys update I got the replacement CXA chip (i think original too) same resistance as the original chip. I replaced it and sure enough resolved the interference issue! I am super happy and super relieved that my console is now back to normal working conditions!

Also I did try the cap network with tapping from the back of the board. That did not work.. then I tried sync on luma + Sync Stripper and that worked perfectly through extron! So that solves the dreaded sync issue once and for all. So all is well.. mostly .

It seems the black bars I was mentioning before is actually Neo Geo CD's ghosting! Very much like Neo Alec found on his front loader earlier last year it seems! I am thinking of doing a full recap! Unless someone has more info on this.

Ghosting in Frontloader NGCD RGB Image

Does anyone know if recapping the video circuits will fix this? I just got this frontloader, and there is ghosting in the image (you can see it to the right of objects in the solid colors). Tested the toploader with the same scart cable and capture device, and it doesn't have the issue. The same...

www.neo-geo.com

 

[Neo Alec]

Sync on luma is tried and true. Did the stock sync on composite not work with your stripper?

 

[LordKirkis]

Sync on luma is tried and true. Did the stock sync on composite not work with your stripper?

I did not get around to trying since I jumped the horse and ended up modding the console. Not sure if still an option, but Luma works great for sure.

 

[Neo Alec]

I did not get around to trying since I jumped the horse and ended up modding the console. Not sure if still an option, but Luma works great for sure.

Yeah, you probably would have been fine not modding it. The only reason I bother with CSYNC is because I don't use a stripper or anything with my CRT setup.

 

[LordKirkis]

Yeah, you probably would have been fine not modding it. The only reason I bother with CSYNC is because I don't use a stripper or anything with my CRT setup.

Too late and unfortunate. But either way I will do my best to care and preserve it as it is now. The caps will also be replaced and in general I am just glad that I can enjoy the system now.

 

[Neo Alec]

Yeah, I think some of these CSYNC mods need disclaimers attached. That CSYNC mod on retrorgb especially needs one or to be removed because it's not right.

 

[LordKirkis]

Yeah, I think some of these CSYNC mods need disclaimers attached. That CSYNC mod on retrorgb especially needs one or to be removed because it's not right.

True. Nearly screwed up my console.