Reset Boot Test (Neo Geo AES)

the next step after confirming your power rails are good is to test if you are getting basic video out the best test for this allows us to bypass all of the following key items that are not required to even be present on the board or working 69k cpu bios z80 cpu memory card ics controller ics yamaha sound & headphone ics palette ram (cxk5864bsp) video ram (cxk5814p) for lspc video ram (cxk58257am) for lspc cmos mask rom (tc531000) for lspc the below test if it works confirms the lspc, neo g0 (or 74ls245 on early models) and cxa are all working reset boot i term this test the reset boot , because all you have to do is keep the reset button permanently held and turn on if you do this, after a few seconds you should see jumbled graphics on the screen or faded white to black, or faded red to black, similar to under voltage screens the output depends on the presence and state of the video and palette ram even though they are not needed to be installed or working they will change what is display on screen the key here is we are looking only for an actual output on screen, whether it be black, faded gradients or garbled screen a screen output is confirmation the lspc and cxa encoder, power supply and av cable are all good if you see nothing on screen, continue the tests below to confirm the lspc is working and then the neo g0 (or 74ls245 on early models) and cxa are all working make sure to test both composite and rgb for video output sometimes the rgb won't be working or wired up right, and other times the composite might not work but the rgb will there can be a fault on the board where the csync pin outputs just the hsync pulses but no vsync, but composite will work so it helps to test both diagnostics rom once you get basic video output to the screen, it is recommended then to install a diagnostics bios to test the rest of the system if you do not yet get any video out, continue to the tests below confirming lspc testing d0 15 activity as a basic check the lspc is working, it is easy to just probe the d0 15 pins (almost always the first pins around pin 2 to 30, depending on revision) turn on the console with all components installed, and probe the pins 2 to 30 on the lspc looking for basic pin activity if you see activity on most pins you can generally assume the lspc is running if you have a bad z80 cpu, 68k, work ram, bios or other things, you will not be able to check the lspc activity on d0 15 pins as it requires those to work however, you can check all other pins of the lspc even in reset without any processors, ram or bios present fv video ram activity the lspc uses fv video ram of cxk5863p (28 pin) or cxk5814p (24 pin) sram the address and data pins connect to the lspc on the cx and fx pins (or on early revisions labelled fv ax and fv dx ) turn on the console and monitor for general activity on these pins if you do not see activity, its likely your lspc is dead or has shorts on it, or is missing power or clock signals if you hold reset while powering on, the pins should show random data if you do not hold reset, and you have no game in, it should show solid data (for blue or white screen depending on bios and state of console) sv video ram activity the lspc uses sv video ram of upd43256 or cxk58257ap sram the address and data pins connect to the lspc on the bx and ex pins (or on early revisions labelled sv ax and sv dx ) turn on the console and monitor for general activity on these pins if you do not see activity, its likely your lspc is dead or has shorts on it, or is missing power or clock signals if you hold reset while powering on, the pins should show random data if you do not hold reset, and you have no game in, it should show solid data (for blue or white screen depending on bios and state of console) sync / divi output the sync output goes to the cxa1145 and is required along with the rgb pins in order for the receiver to recognise rgb video output confirm you see 15 74khz sync pulses on the sync pin (lspc a0 pin 126, lspc a2 pin 150) also confirm it reaches the cxa1145 pin 10 you should also see periodic low long pulses signifying the start of frames you will need to capture on a trigger that detects over 10us long low pulses, and then check the timing between them also matches the correct timing todo image of vsync part of vsync also confirm you see 3 579mhz pulses on the divi pin (lspc a2 pin 143) if you have an lspc a0 revision, instead check the cxa1145 pin 6 has that pulse (it is fed directly from the crystal on a0 revisions, not the lspc) confirming neo b1 if your lspc is running and you see pulses on fv, sv and d lines, your next step is to check the neo b1 chip is working the neo b1 chip processes graphics and sets the palette ram address pins working in conjunction with the lspc/neo g0 to set the rgb data that goes into the flip flops, through the resistor ladder and ultimately to the cxa1145 confirming video encoder if you have an active lspc and neo b1 but still don't get any video out, check your cxa1145 video encoder with an oscilloscope check you have valid red / green and blue in pulses (around 1 2v pulses) check you have valid red / green and blue out pulses (around 1 2v pulses) check the xo out and xo in have 3 579mhz pulses check you have composite out signal check you have csync in and out pulses (15 74khz sync pulses, with longer low pulses indicating full frames for vsync) confirming av port if you have all valid signals from the cxa1145 chip, make sure the composite out and rgb out, and csync if used, make it to the av port pins if they don't check the resistors, capacitors, inductors and traces between the cxa and av port check av cable if all of the above check out, it might be worth testing your av cable for continuity from pin to pin (end to end), or replacing it