Help with NEC XM29plus RGB - consoles and Jamma

[juanmiglesias]

HI guys, hope everything is fine. I have a couple of questions regarding using RGB mods on my NEC xm29 plus
my setup:

• - I'm not using SCART ready made cables
  - All my consoles are NTSC
  - I used a 15 pin VGA connector internally for every console I mod (snes, n64, saturn, megadrive, psx, jamma)
  - for the BNC rgb2 input of the nec I used a vga to bnc cable straight to the input, no switches till everything is good to go, and for the VGA input I use a regular VGA for naomi, mame pc.
  - What I did was use the standard VGA pinout for RGBs and ground.
  - if a system needed caps or resistors I add them internally from the video connector to the VGA connector.
  - extron PA 250 (that I'm not using right now)
  - for med res and testing I used a GBS 8220 v3
  - extron VSS100 (I use it sometimes to test sync con C-video)

I based my cables as if they were scarts just by replacing the scart connector for the VGA, following these guide:
Consoles:
http://members.optusnet.com.au/eviltim/ ... escart.htm
Jamma:
http://www.geocities.ws/podernixie/htpc/cables-en.html

for SNES:

• - from the AV connector points to the VGA I added 220u caps in the RGB lines,
  - sync from csync, no resistor or cap.

for N64:

• - I use the lines straight from the RGB IC, use the amp, add a sync stripper, and basically follow retrorgb guide.

for Saturn:

• - Straight RGB and sync.

Sega Genesis 2:
- can't get it to work, tried following the scart cable guide without luck, also the csyc guide on retrorgb (http://retrorgb.com/csync.html), also a sync stripper.
read that xm29plus doesn't get along gensis sync, so I might try a rgb bypass if no solution comes.

All consoles worked, snes was saturated before caps, added them and it was fixed, n64 worked at the first try, saturn also worked with no issues. jamma was oversaturated from a naomi but I did not had the scart schematic (resistor on rgb and sync), but it worked.

my question are basically these:

• 1. I noticed another guide asking about adding resistor or caps to sync (http://retrorgb.com/csync.html), is this mandatory?
  2. any insight for genesis 2 and nec xm29plus.
  3. I don't exactly get this 0.7Vpp 75ohm analog input standard, doesn't mean 0.7 is the minimum, maximum, or it has to be stable at 0.7?, is it measurable with a regular multimeter? if I try for example to measure the snes by using ground and R for example I get around 2v, on saturn around 1v, and it also varies, is this expected? do I need to lower it to a 0.7 with more resistors?
  4. is Jamma diagram ok for any 15khz board?
  5. also anyone knows if the nec supports med res?

I just want to be 100% sure everything is ok before start using the nec for long periods of time, don't want for anything in the world to do something that can shorten its life because of a noob mistake, as you can see I have a basic-moderate knowledge on electronics, so I just want to hear from the experts before continuing on finishing my retro setup.
thanks!

[juanmiglesias]

I also forgot, about SYNC, the two types of Csync, TTL and 75 Ohm, I noticed on the website at retrorgb that some consoles is suggested to use a resistor or cap for 75ohm, is it necesary for TTL?, I see in the manual the NEC supports TTL 0.7-4.0 (I guess this is the range it takes), and 75 Ohms.
Any other relevant info about sync types?
thanks again.

[xga]

Which specific model do you have? XM-2960?

[juanmiglesias]

Yes that one, Xm-2960

[xga]

Fairly certain that the XM-2960 can't do 24 KHz / Med res. 15.7 KHz / 31 KHz to 65 KHz only. There are other models in the XM29 / XP29 range that can do 24 KHz though.

[juanmiglesias]

That's what I suspected, I think the xp29 is the one that supports med res.
Thanks!

Btw so you have any insight in the other questions?

[xga]

• 1. I noticed another guide asking about adding resistor or caps to sync (http://retrorgb.com/csync.html), is this mandatory?
  
  I haven't read Bob's new csync page in detail yet, so can't really comment. The NEC XMs and XPs need csync though. If you've got a kick ass monitor like the NEC, don't do anything by halves and use good quality cables.
  
  2. any insight for genesis 2 and nec xm29plus.
  
  Can't see any issue with running a Genesis 2 on a NEC XM29plus. What is your concern?
  
  3. I don't exactly get this 0.7Vpp 75ohm analog input standard, doesn't mean 0.7 is the minimum, maximum, or it has to be stable at 0.7?, is it measurable with a regular multimeter? if I try for example to measure the snes by using ground and R for example I get around 2v, on saturn around 1v, and it also varies, is this expected? do I need to lower it to a 0.7 with more resistors?
  
  Voltage is peak to peak. Can't measure properly with a multimeter, you need a scope to measure correctly.
  
  4. is Jamma diagram ok for any 15khz board?
  
  Not sure what you mean? Are you wanting to use something like a supergun to connect JAMMA boards to the XM29? If yes, then that should work fine.
  
  5. also anyone knows if the nec supports med res?
  
  Already discussed.

!

[juanmiglesias]

• 1. I noticed another guide asking about adding resistor or caps to sync (http://retrorgb.com/csync.html), is this mandatory?
  
  I haven't read Bob's new csync page in detail yet, so can't really comment. The NEC XMs and XPs need csync though. If you've got a kick ass monitor like the NEC, don't do anything by halves and use good quality cables.
  
  2. any insight for genesis 2 and nec xm29plus.
  
  Can't see any issue with running a Genesis 2 on a NEC XM29plus. What is your concern?
  
  3. I don't exactly get this 0.7Vpp 75ohm analog input standard, doesn't mean 0.7 is the minimum, maximum, or it has to be stable at 0.7?, is it measurable with a regular multimeter? if I try for example to measure the snes by using ground and R for example I get around 2v, on saturn around 1v, and it also varies, is this expected? do I need to lower it to a 0.7 with more resistors?
  
  Voltage is peak to peak. Can't measure properly with a multimeter, you need a scope to measure correctly.
  
  4. is Jamma diagram ok for any 15khz board?
  
  Not sure what you mean? Are you wanting to use something like a supergun to connect JAMMA boards to the XM29? If yes, then that should work fine.
  
  5. also anyone knows if the nec supports med res?
  
  Already discussed.

!

Hi thanks for the reply.
1. I am actually using good shielding and cables inside the console with quality parts to actually avoid problems with the cables, I'm fairly good at soldering and of course I use isolation in every single solder point and cable, then it goes to a regular vga to bnc pro cable, once I figure out all the values are right I will use oshpark to get me some nice internal pcb done. I also ordered some scarts for testing purpose. My whole idea behind avoiding scart was to built a custom setup, I already have a PCB designed for a RGB switch much like the gscart, which technically can use scart or vga plugs, but that is a whole different story, once I got everything right here I'll resume that project.

2. Genesis 2 is not syncing on my nec, composite works great, double checked soldering points, added caps and resistors, also wrote Bob with the same info on this post and he replied too (really cool btw), he says genesis 2 has a weird sync, and will follow up with him about the gen2 and my different tests.

3. I do have an oscilloscope but it is old, and really never used one, any insight or tutorials to start with? is it even work for this task?
Tenma model 72-720 (same as the image)


4. for the JAMMA, I installed a complete arcade setup, the audio goes to a speaker to rca converter, then to the audio receiver, then for the video, I use the jamma lines with the diagram for scart of the page.

5. yes thank you for confirming this, is just that a couple of posts mention trysinc on nec, but I think some are mistaken XP with XM series.

btw I found this on the manual:
on the sync:
""Separate sync, TTL level 0.7-4.0Vp-p/75 Ohms...... rgb2 (bnc) only""

I'm still confused with TTL and csync :/

sorry if there is a couple of newbie questions over here, just want to go through with everyones opinions before making assumptions based on other posts.

[juanmiglesias]

UPDATE:
Genesis 2
1. had the red and sync traces broken, but odd thing it looked like something not human made, this was a preowned machine.
2. tried the RGB with the extron VSS110 c-video sync stripper and it worked.
3. still csync won't sync on my nec, also I tried with a cap and resitor on the csync 220uf and 470ohm, no luck
4. will add an lm1881 circuit to it.

SNES:
tried the 330 ohm on the sync and it actually couldn't sync, remove it, and everything back to normal :/ is the resistors on sync only for tvs with SCART inputs instead of BNC RGB inputs?