Help setting up a testbench!?!

[VintageGmr]

Hi guys, i need some help setting up a testbench where i can hook up my pcbs to test them without putting them in and out of my arcade cabinets.

Anyone have any good "how to" videos or walkthrough's on setting one up with power supply, monitor and harness and everything?

 

[twistedsymphony]

you're going to get A LOT of varied opinions here.

IMO a good test bench is just the guts of an arcade cabinet laid out on the table.

Mine personally I have a JAMMA harness and the power is wired into a NAOMI PSU the video is going to an RGB SCART connector with an RGB SCART capable monitor, There's a speaker wired to it and the controls are wired to a Blast-City panel... Thats it! I also have some buttons just wired into the harness for Test, Service, and Coin.

I also have one of these "JAMMA tester with Buttons": https://riddledtv.com/jamma_testers.html#TesterButtons

I like this setup because I can use the PSU to run JVS boards directly and I can use it to test panels also by just swapping out the panel connectors. and the same monitor is used for testing consoles.

the JAMMA tester board is nice because I have access to all the buttons that pass through the jamma edge without even needing a panel connected, and it's got a voltage monitor on it for good measure.

This is a pretty simple setup assuming you already have a monitor, speaker, and PSU it's just buying a JAMMA harnesses and soldering on some connectors.

 

[LittleLarrySellers]

+1 on Riddle's jamma tester. Makes it so easy to do basic tests of pcbs w/o controller hooked up.

If you need good video on the power supply, Vintage Arcade Gal has a great one:

View: https://youtu.be/UvmkMvlzHew?si=7HXStPDhG8-6XcUo

 

[hatmoose]

I think what might help is a SuperGun

This is a device that plugs into your JAMMA board and interfaces it with power, video and controllers.

There are a massive variety of Supergun but the two that get the most discussion here on Arcade Projects are
1) HAS - this is the Ferrari of superguns they are sought-after collectors items in their own right. Normally they sell out in minutes.
2) Minigun - this is a FOSS project from FrankFJS, they are easy to make at home with basic tools. There is at least one reliable seller on these boards

 

[twistedsymphony]

I typically recommend against superguns for a bench setup. They often have video converters, or non-standard audio wiring, or weak/non adjustable PSUs, or control adapters. These things are fine in a lot of cases, but if you're using this to troubleshoot a board it's just adding layers of unnecessary complexity that can have you chasing down non-existent problems.

If you're having video problems how do you know the problem is actually with the board or with the board's compatibility with the supergun's video circuit? how do you know audio problems are with the board or with the board's compatibility with the supergun's audio circuit? etc.

I would argue that if you're going to use a supergun on a bench, you need to have intimate knowledge of how it's designed, how that design differs from a normal cab, and how that difference typically effects a PCB. otherwise you'll likely find yourself chasing down supergun design issues rather that PCB issues.

 

[VintageGmr]

So I am trying to set up a testbench, and so far i have an old tv. My thoughts was that i could hook up the jamma harness with a scart plug and hook it up to the tv.

I can get a picture but not any colour.

Just to be clear, this is not the final setup, i need it to work before i build my rig. This is just "twist the cables and test stage" also waiting on a new jamma edge connector in the mail.

Is it a way to make this work? What am i missing here. I have the ground to video ground and synch cable to synch.

The wiering in the scart cable is a bit tricky though..

Any insight or help here would be greately appriciated.

 

[twistedsymphony]

you'll want some 330ohm resistors inside of the SCART plug in line with the Red Green Blue and Sync wires because JAMMA outputs higher voltages than the SCART standard.
you'll also want to make sure you've hooked up video ground to pins 4, 5, 9, 13, 17, 18, 21

There are many different diagrams online for how to wire JAMMA to SCART. but I've personally found that 330ohm resistors, no capacitors, works best (at least on my display). I leave the 12V and 5V completely disconnected.

Audio is a whole other discussion
Essentially you're converting "Balanced Amplified Mono" to "Unbalanced Line Level Stereo".
You can get "line level converters" for car-stereo applications that will do this for about $10 but about a billion DYI opinions online, most of which will be wrong.

The important thing that most people get wrong is that "Speaker Negative" IS NOT GROUND, in most cases it's a inverse wave form from Speaker Positive. This is done to boost volume and improve clarity (it eliminates ground loop buzzing and other noise). this is the difference between balanced (speaker negative is an inverse wave form) vs unbalanced (speaker negative is ground),

Some boards do actually wire ground to the speaker negative pin, but a lot of boards do not. you're completely safe if you treat all JAMMA audio output as balanced, but you are NOT safe if you treat it as unbalanced and the board happens to have balanced output.

The best answer I've seen to do this DYI is this post here: https://electronics.stackexchange.com/a/12205
you'll want the diagram in the lower left (Balanced in to Unbalanced Out) you'll want 2W resistors because of the power involved. you can then simply split the output of that to both Left and Right Channels.

 

[VintageGmr]

Never mind. I figured it out!



The wire for RGB Blanking had to be hooked up with the synch connection.

I even figured out the audio. So now it all works great.

Awesome. So now i am on my way to start setting up my test bench.