No power to fuse on RaspberryJAMMA board

[tonyperkwx]

Hi everyone. I've been attempting to get a new RaspberryJAMMA board (ArPiCade) working to no avail the last few weeks. The board is getting +5V power at the Jamma edge connection, but there is no power going to the Raspberry Pi. I'm using a 3b+ Pi.

The fuse on the RJ Jamma board had no continuity on it, so I replaced it with a 2.5A fuse. Now there is continuity across the the fuse. But when powered up, there is no DC power flowing across the fuse. So something between the edge connection and the fuse is not working.

I've put too much money into this project already to gamble buying another ArPiCade board. I'd appreciate any help troubleshooting this issue or where to turn for help!

[dee2eR]

If you have blown the original fuse did you figure out why it blew? There's nothing between the edge connection and the fuse that could have failed (except PCB track damage maybe).

How long have you had the board? If it doesn't work can you return it to the point of sale for a replacement? Or is there some sort of issue returning it?

Have you checked if the RPi works if powered through the regular USB power input (while not powered through JAMMA)? If the fuse is good and the Pi is good the only other part it could be is the ribbon cable (unless there's damage to the RaspberryJAMMA PCB itself).

It may be worth checking the power pins of your SD card for a short circuit too, I've had that happen with one card before and it would blow fuses instantly.

[tonyperkwx]

Thanks for the reply! The original fuse may have blown because the 3b+ tried to pull more than 1A I assume? The voltage was a little high around 5.6V, and I have since switched to a new switching power supply which dials down to 5.4 at the edge connection of the board but no lower.

I have not connected the Pi again since replacing the fuse as I don't want to risk damaging it until the board is powering correctly and I can measure the power output through the 40 pin header on the rapsberryjamma board.
The pi itself still works fine externally. Here's a dumb question... will there be any current going through the fuse if the pi is not connected?

There could be damage to the RJ PCB which is what I fear that occurred when the fuse blew. I thought perhaps there would be little to few components to troubleshoot between the edge connector and the fuse if the fuse was able to protect the downstream components.

[dee2eR]

5.4v (or 5.6v) is a bit higher than I'd recommend, typically with a Pi3B+ you will want about 5.1v at the JAMMA edge (no more than 5.2 should be needed). What kind of power supply do you have? I haven't seen any JAMMA supplies that couldn't be turned down to a nice 5.1 ish volts at the board. A JAMMA power supply should be able to be adjusted to account for the different power requirements of different JAMMA boards, I've seen 5.6v cause damage to JAMMA boards before.

Without the Pi attached there's no reason for current to flow through the fuse. The other elements on the RaspberryJAMMA are not fused, it's really just there to protect the Pi. Assuming you bought the RaspberryJAMMA recently the fuse would have originally been a 2A, which should have been fine for a RPi3B+. The older 1A fuse wouldn't blow using a RPi3B+ but could act as a current bottleneck as typically the current draw of a Pi3B+ in a JAMMA setup is just under or around 1A. (I guess technically the 3B+ could blow the old 1A fuse but I haven't seen it happen before).

The track running from the JAMMA edge to the fuse is pretty big, you should be able to see any damage pretty easily just having a look at the underside of the RaspberryJAMMA. If there was a short circuit involved in blowing the fuse it's possible to damage PCB tracks... you would probably notice a burning smell at that point though...

[tonyperkwx]

The new power supply is a Happ Power Pro from Arcadeshop. I can dial it down to about 5.4V or up to 7.0V. If that range isn't expected, I can look into getting a replacement.

The original power supply that was used when the fuse blew was a linear that was putting out probably 5.6 to 5.8V... I don't recall which of those two numbers, which I only checked after the issue because the original game in it that required +5V was running fine, so I never gave it a thought unfortunately.

There is no visible damage or smells to the RJ board.

[dee2eR]

That range doesn't sound right. Typically you want about 5v. As you have had 2 power supplies measuring so high it could actually be whatever you're measuring it with that is out though. Happ is a good brand, I assume they can make a 5v power supply that puts out 5v...

Are you measuring at the JAMMA edge with a board attached? If there's nothing attached it could account for the odd numbers you're seeing. Typically you want the board attached whe measuring the voltage to account for the current draw and drop from the board and the wiring.

Still not sure why the RJs fuse is blowing in your cab. What was the original game in the cab? Is the cab wired to JAMMA standard? (I ask because linear power supplies are more common in older pre JAMMA standard games, some pre JAMMA games had the same size edge connector...)

[tonyperkwx]

The voltage is measuring the same at the power supply terminals with the RJ board attached (but not the Pi attached), and at the edge of the RJ Jamma board. The seller said the same thing, to test with the board attached. Since the RJ isn't drawing power usefully, it may be the same as testing with no board.

The cabinet is a non-jamma Super Pac cabinet, which is original hardware and fully working with the original linear PS. I'm running it through a Super-Pac to JAMMA converter. That was the configuration when the fuse blew.

It sounds like I don't have anything to lose by testing it out with the Pi again at this point, probably an older Pi first that I don't use anymore as a smoke test.

[tonyperkwx]

After all that power paranoia, the setup mostly works after I plugged the Pi back in and gave it another try. It's fine with the voltage but plays blind, showing only a white screen. I tried it both with the 240p and 480i modes in config.txt to the same result. If I disconnect the HDMI, it still shows all white on the monitor.

To test the video conversion hardware, I set the mode to 480p in config.txt and hooked up a VGA monitor to the converter output. The output was fine to the screen. I also tried 480i to the monitor but I don't think it supported it as it showed no signal.

I also tested the Pi output on hdmi to a hdmi monitor, while set to 240p, and the monitor correctly identified and displayed it as 720ish x 240 x 60hz.

I also tried a different jamma board and the video output from that is just fine to the monitor using the Super Pac to jamma converter.

Any ideas about the white screen?

I really appreciate the troubleshooting help!

[dee2eR]

Odds are something else on the RaspberryJAMMA died when the fuse went the first time. My guess is either the video amp chip (most likely the issue I would think) or the chip that combines the H & V syncs into C sync has been damaged.

If you're handy enough with the soldering iron to do surface mount parts changing the video amp shouldn't be too hard. If surface mount is too hard the part is also often available on eBay pre-mounted to a DIP8 converter (and at 10x the normal price...). I can help you find the part or supply it to you if you need.

[tonyperkwx]

Thanks, I'll send you a PM. If it's resolved I'll update this post with the solution.