Problems with building my own supergun / jamma test rig

Hello everyone,

The last time I posted new thread someone told me that I should do some introduction to myself so there I go .

INTRO

My name Is Marcin, I'm from Poland I'm a retrogaming enthusiast like most of you I think . Currently I own over 60 consoles (many doubles) and a collection of over 850 games in total. It is hard for me to pick just one favorite system so I picked three - NeoGeo MVS (or arcade in general), Sega Genesis and NES.

That much for the general info. Now about my background in arcade. I'm collecting arcade games for like 3 years now but I played MAME since I was 10 or so :P. Most of my collection consist of MVS cartridges although I have some arcade PCBs as well and an actual vintage arcade cabinet. I also have my raspberry pie set up to work with crt tv and recently I digged out my old pc to try out the groovy mame. Apart it is loud as hell it otherwise runs beautifully. Two years ago I consolized my first MVS system and since then I did two more and bough a supergun online from Retroelectronik (i hope I haven't misspelled the name). Since then I always wanted to take on the project to create one for myself and here is the reason why I'm starting this thread .

I hope you guys will help me with the issue I came across. Please note that I do not have any electronic education whatsoever so I hope for your understanding. All I know is self thought through learning by doing. Oh and my English is lacking in some areas so please forgive me that too .

DESCRIPTION

Recently I've put together a supergun setup using ATX power supply from an old PC. I took care to pick a PS that supports -5V line. Firs I got rid of the all unnecessary cables and left only what is essential. I forgot that to start a PS I need to shorten the "PSU ON" with the ground so I need to add the momentary push button later on this project but for now a simple bridge with a cable will do.

I wired everything as in this schematics:
https://mega.nz/file/O34H1boK#MWyqB_Cq7DyIjPWiZGaQbVPVE3OFK-XN-Acduv3evVk

Then I connected the wires to the SCART socket like so:
https://mega.nz/file/uqwjQbRZ#EIQwfWAznZqK-cctlJX8HjRpTJlYKsqcru98FPk6VNQ

And... It does not work :/. I thought of some issues that may occur so also did this things:

- I've checked if the PSU actually works on an old PC. It did.
- I've checked weather the power cables after reattaching them together are at the same position as before de-soldering.
- I've checked with continuity test if there are no broken wires.
- I've checked the power switch for continuity when it is in its ON position.
- I've checked whether the game boots on the other hardware.
- I've populated the JAMMA cable with missing wires (except for key) just to be sure.
- I've checked if the jamma edge connector and SCART are connected in a proper manner.
- I've checked several different power cables and yes they work (PC turns on and the PSU in my supergun starts quietly buzzing when turned on).
- The fuse on the PSU is intact. Also checked with continuity test.

Then ting that I know I did wrong is when I put 22 Ohm resistors on RGB signals instead of 220 Ohm ones but I doubt I would change anything is case of simply working.

I've ran out of ideas what cloud I did wrong here. Probably it is something simple. Something that I cannot see... So I need someones help on this. I will try to make some pics of the actual hardware although it is a tangled mess so don't hate me :P.

Many thanks for any help! I would appreciate even smallest advises !

What arcade boards are you testing with? I would check voltages at the jamma edge with your supergun plugged in and turned on. It's possible that a fuse is blown on the arcade board or that there is not enough amperage to drive all the components. Also what display are you hooking this supergun up to? Could be out of tolerance sync, but you should at least get audio that way. Also make sure you didn't mistake the 5v and -5v lines coming from the PSU

Use a voltmeter to check the voltage coming out of the power supply. Check the voltage at the PCB edge, as well.

Check the voltage on the SCART "trigger" pins.

SpamYouToDeath said:

Use a voltmeter to check the voltage coming out of the power supply. Check the voltage at the PCB edge, as well.

Check the voltage on the SCART "trigger" pins.

Click to expand...

Second this with additions; what PCB are you trying to make work? Google to make sure its not sensitive to variances in the 5V rail. Some boards don't seem to care if you are off at 4.98 or 5.02 but some boards are picky AF about their 5V line. It could be that it is WORKING, just not with the board you are testing it with.

If you get all the proper voltages at the JAMMA edge, then yes check your video circuitry / cables...make sure its not WORKING but not getting an image.

If you have one, or have access to a scope, you can check to see if you are getting a video signal on that. Granted it won't look like perfect NTSC signal, but you should still be able to see frames with color burst / sync signal before the frame.

I'd really google the PCB you are using though. It could be as simple as THAT PARTICULAR GAME hates the power supply.

Hi.

First of all, check if the TV you're using has RGB. Some TV's have SCART, but not all support RGB. Do you get any sound of it?

And you don't need the +5v on pin 16. Just put a 560ohm resistor between pin 8 and 16. Then tie a +12v wire to pin 8 and you're good to go. That'll make you 4:3 ratio right away without the need to manually switch.

Is it playing blind?

Sorry that I haven't replied for so long. My previous PSU died on me and I didn't have the patience to fix it so I needed to get another one.

Regarding your questions:

I'm trying to run bootleg King of dragons and various MVS cartridges. The games are running fine with my other supergun from ebay so it is not an issue of a broken fuse. The fuses I use within the supergum I'm making are intact to.
I'm hooking the supergun to my 30" CRT Panasonic TV. Again - works fine with the supergun from ebay. It has RGB and the very SCART socket my supergun is hooked up to is described as RGB.
I'm not getting any sound as well.

I think I've found a problem though. I've checked the voltage on Jamma 5V rail and there is a voltage drop to about 3,8-3,9 V. I'm wondering why is that so since measuring the voltage on PSU itself returns correct values. Maybe that is my mistake but I made the 5V line (single wire) go from PSU to a 10A fuse and from there it propagates to all places that require it. Should I rather connect those places directly to PSU?

Atro said:

Hi.

First of all, check if the TV you're using has RGB. Some TV's have SCART, but not all support RGB. Do you get any sound of it?

And you don't need the +5v on pin 16. Just put a 560ohm resistor between pin 8 and 16. Then tie a +12v wire to pin 8 and you're good to go. That'll make you 4:3 ratio right away without the need to manually switch.

Click to expand...

Cool tip. Noted down . Thank you!

Cloud said:

Sorry that I haven't replied for so long. My previous PSU died on me and I didn't have the patience to fix it so I needed to get another one.

Regarding your questions:

I'm trying to run bootleg King of dragons and various MVS cartridges. The games are running fine with my other supergun from ebay so it is not an issue of a broken fuse. The fuses I use within the supergum I'm making are intact to.
I'm hooking the supergun to my 30" CRT Panasonic TV. Again - works fine with the supergun from ebay. It has RGB and the very SCART socket my supergun is hooked up to is described as RGB.
I'm not getting any sound as well.

I think I've found a problem though. I've checked the voltage on Jamma 5V rail and there is a voltage drop to about 3,8-3,9 V. I'm wondering why is that so since measuring the voltage on PSU itself returns correct values. Maybe that is my mistake but I made the 5V line (single wire) go from PSU to a 10A fuse and from there it propagates to all places that require it. Should I rather connect those places directly to PSU?

Click to expand...

I don't know if the fuse is causing the voltage drop but it's worth a shot to take the fuse out and see if that helps

Cloud said:

I think I've found a problem though. I've checked the voltage on Jamma 5V rail and there is a voltage drop to about 3,8-3,9 V. I'm wondering why is that so since measuring the voltage on PSU itself returns correct values. Maybe that is my mistake but I made the 5V line (single wire) go from PSU to a 10A fuse and from there it propagates to all places that require it. Should I rather connect those places directly to PSU?

Click to expand...

Check the voltage on each side of the fuse. If the fuse is causing the voltage drop, then measure the current through the fuse. If the current looks reasonable but the voltage drop is still >1V, then get rid of the fuse. The power-supply probably already has protection on its outputs (read the manual).

If the fuse isn't causing the voltage drop, then you might need a beefier power supply. What's the current rating on the 5V supply? What board are you using, and how much does it require?

Voltage might be from the wire you are using, you said single wire but what gauge? Don't use anything smaller than 18awg and even 18awg I wouldn't run longer than 3ft if only a lone wire, run at least two if 18awg. It could also be from the PCB itself depending on what power requirements the mono has. Check voltage at the jamma edge then check it on a chip that's furthest from the jamma edge, there should be a slight difference but nothing crazy. If you are seeing 5.00v at the edge and then 3.5v at the furthest chip, you either have a short on that PCB (Which you say works on the other SG fine) then you may just have a weak power supply that can't provide enough current. 10A on the 5v rail is retarded anyway as most systems won't go over 6A.

OK I have some updates.
It seams managing cables helped a bit. I've ran every power wire directly to the PSU and it helped somewhat. Only ground cables are clustered together since there are to many of them :P. When I measure the current on the cables they give me such values with my new PSU:
5V line: 4,85 to 4,9 (4,75 on the game edge).
-5V line: -5,75 (same on the game edge)
+12V line: 12,05 (same on the game edge)
This measurements were taken without the JAMMA cable added (game directly attached to the SG). Adding JAMMA cable to the mix drops the voltage on the game edge by about 0,05V.
Also I need to mention that at the moment I've bypassed every resistor or fuse on the power lines. I'm using cables scavenged from some old broken PSUs so they are quite thick. At least on power lines. The length of wires from PSU to JAMMA edge is about 60 cm (about 2 ft). Same for JAMMA cable. The wires are quite thick too (the core is about 1mm so it falls under 18awg requirement).
Oh and here are the specs of PSU itself:
https://mega.nz/file/q35SXTQZ#LRnHNzAZFw72tOLQlM50xFPBDQ7ynf0GpJpeRdlfdcE
-5V line is supposed to be 0,3A but the guy I bought the PSU from made some changes and now its is about 1A.

After making the changes as I noted above I've received some positive feedback from the games. I've checked two of them:
- King of Dragons (bootleg) - now it gives me some picture but is completely distorted white noise and the picture occasionally goes to a black screen or alternates from "AV4/RGB" to just "AV4". Also you can hear the white noise.
https://mega.nz/file/v2hQAJiT#q_svQU4gOUxF8J9nYZGS8L-HL7fvG1uVEl6C2zVzYvU
I've also made a clip:https://mega.nz/file/r24SBDLQ#a8hLoD4gs0JBoft1EhTUeSe8U5hjqFjL09evW6iJFeM
The sounds in the background are from my other TV :P.
- Bubble Bobble via MVS system. This time it looks way better but the image is still distorted and very much yellowed. The sound is fine though. Have a look.
https://mega.nz/file/f34ShRSB#eAkjUVyYb3QXqIuj17_pOOXcXP4vQM_TxOPbdWd4Jjw
https://mega.nz/file/bqwG3R5S#LZMQaG0j1_jTIqBmQXy38KPhXwkLkBpY073sbyCqVx8

I think I will also change the 22uF capacitors for RGB lines and exchange them to 220uF as in the original design (I'll let you know how it worked) but except for that I have no clue what to do next to get a clearer picture or to get the King of Dragons to work :P.

4.75v might not be enough for the board to function properly. Have you looked inside the PSU? Perhaps there's a bad capacitor on the 5v rail? I find it odd that -5v is -5.75 but 5v is only 4.75. If there is any adjustment pots on the 5v line I'd try turning those up a bit to see if you can get 5v at the edge.

If it's 4.75v on the game edge then most likely it's 4.6-4.7v on the chips furthest from the edge so it's not going to function properly, most need at least 4.8v. Adjust your 5v line, SLOWLY to about 5.1v and report back.

I'm also skeptical of the guy's work changing the amperage from .3A to 1A. Worth looking at