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Roxbury
25th June 2006, 08:13 PM
I fired up a Wonderboy PCB I obtained untested a few weeks ago (original Sega) and it worked OK apart from a minor sprite glitch. I fired the board up again, and all I get is a very warped distorted green washed screen that you can just make out some graphics on, the screen also scrolls vertically. I know I might need to do some research on this, but can anybody offer any advice on what might be wrong? The linked picture shows a bit of a screen shot. :cry

http://tehkella.net/damian/WonderboyProb.jpg

MadMikeAU
25th June 2006, 08:15 PM
Last time I saw an image like that, it was due to the Video Ground not being grounded. Check that out on both the board and the cab side.

Roxbury
25th June 2006, 08:43 PM
Good point. The pinout for Wonderboy doesn't list a video ground, but I assume that on my harness I should have a wire from the video ground point on the jamma connector to a normal ground point on the board connector?

PS while I'm here while I was making the harness I ran out of one type of green wire, and used a different thickness green wire to finish off. I didn't think anything of it, but just realised I have 2 different thinknesses of wire for video colours & sync. I wouldn't have thought it would make a difference, but now the board has played up I am now wondering......

MadMikeAU
25th June 2006, 08:53 PM
Electrical current is like water, it follows the path of least resistance. If you have 2 different gages of wire, you make a path of least resistance to the larger ones.

The grounds and power (+5, +12, etc) wires should be bigger than the others.

My cab originally didnt have anything wired to video ground. I ran a wire from video ground to ground and it fixed a lot of issues with some boards/projects.

bretty
25th June 2006, 09:14 PM
I also have the same prob with some boards.My cab doesnt have a wire for video ground but then the board pinout does not list one either.So running a wire from vid ground to ground wont help will it if theres no wire on the other side?

MadMikeAU
25th June 2006, 10:39 PM
I also have the same prob with some boards.My cab doesnt have a wire for video ground but then the board pinout does not list one either.So running a wire from vid ground to ground wont help will it if theres no wire on the other side?

True.

It means not enough electrons are getting to the video output. Check the voltage of the cab. Some early Sega stuff is very intolerant of low voltages. Thats the prob with my Choplifter, anyways.

Then again, could be a dead cap, or something else creating those symptoms

Roxbury
25th June 2006, 11:34 PM
I just checked my cab and the Video ground pin (14 parts side) on the connector is not wired to anything. Sorry if this is a basic question (I still worry about power stuff) but I assume I can run a wire from Video ground on the connector to ground on the power supply? On my power supply it has terminals marked DC COM, this is where I traced the other grounds back to. There is also a terminal marked GND but there is nothing on this. What is the difference between DC COM & GND on the power supply, I thought they were the same thing?

Johns-Arcade
26th June 2006, 01:25 PM
I just checked my cab and the Video ground pin (14 parts side) on the connector is not wired to anything. Sorry if this is a basic question (I still worry about power stuff) but I assume I can run a wire from Video ground on the connector to ground on the power supply? On my power supply it has terminals marked DC COM, this is where I traced the other grounds back to. There is also a terminal marked GND but there is nothing on this. What is the difference between DC COM & GND on the power supply, I thought they were the same thing?


DC com is the common return point for all output voltages from your power supply (e.g 0 volts), whereas GND is the earth connection for your input voltages (240 volt side). Do not connect these together.

Regards,

JWG

Roxbury
26th June 2006, 01:47 PM
Thanks for the explanation JWG. So I can run a wire from video ground pin 14 to DC COM?

Johns-Arcade
26th June 2006, 03:02 PM
Thanks for the explanation JWG. So I can run a wire from video ground pin 14 to DC COM?

Yes you can, but if your game was working a few days ago (except for the sprite issue), I would suspect that you have another problem. Do a continuity test between your monitor video GND and your pcb (with the game off), and see if you have lost a connection. If fact, looking at your picture I'd check all your monitor inputs at the same time.

Regards,

JWG

Roxbury
26th June 2006, 11:55 PM
I have cheated and put a jumper wire from pin 14 on the Jamma edge connector to ground on the harness I made. Now I have a picture, althought the color is a bit off and there is no sound. I have triple checked my harness, so I did some checking in my cab. It appears a couple of the ground connections on the connector in the cabinet are not connected to ground (ie there is a break somewhere along the line). My guess is that some games are more fussy about this (Wonderboy being one of them). I guess a re-wire of the cab is on the cards since it is a bit of a mess.

Roxbury
27th June 2006, 01:21 AM
OK a bit of an update. I think the problem I mentioned above has something to do with my Jamma harness for Wonderboy. I found this old Jamma harness (reeeallly crappy) that came with wonderboy in Monsterland that an op gave to me when I bought it off him. The pinout for Wonderbay is the same, and when I used it it worked as it should (apart from some sprite corruption! The wiring is the same except:

Coin Meter 1 & 2, and Test are not connected on the old harness.

My harness uses a couple of different thicknesses of wire for video connections. I will get things consistent one by one and hopefully eliminate the problem.

Roxbury
27th June 2006, 11:25 AM
STUPID!

Every time I tried my harness I would get a different picture or no picture. Then I had a look at the edge connector on the board and the connector on my harness and noticed there was a bit of room either side. What I had been doing is getting a different short each time I plugged it in! Grrrr, SO SIMPLE!!