two different MSX2s, two different FM Audio cartridges, two different games, same result

Yeah, I tested both slots to make sure they are being read correctly. The Konami game master carts or various game combinations work like Penguin Adventure and Gradius, for example. I've also tried swapping the order of the carts -- it seems like when it does produce FM audio, it tends to be when the FM cart is in the primary slot with the game in the secondary slot. Dunno if that matters much.

I have a megaflashrom SD+ coming in the mail soon enough, so when it arrives I can try the same FM audio games on the flashrom. My only guess would be that, somehow, both Aleste and R-Type carts are messed up in the same way, but that seems like a pretty big stretch.

I'm honestly stumped.

Just to further clarify the symptoms:

-The games always boot up, regardless of the cartridge slot used. In both cartridge slots, the games boot, either with or without FM cart.

-When they boot with an FM cart inserted, the vast majority of the time there is no music at all, the only output being the PSG sound effects in games (like the shots in R-Type). This tells me A) The game can detect the FM cart enough to know to disable PSG music, and B) it's like the FM Cart itself never is started

-No audio output from the FM cart directly through the built-in line port, so it's not just that the audio isn't reaching the mono port on the MSX, it's like the FM Cart itself isn't turned on or something. But, despite that, the game itself knows it's inserted and adjusts accordingly.

I have an original Panamusement FM-PAC, the switch doesn't make a difference unfortunately. It's not that the audio is coming out quietly, it's not coming out at all. With my Sony HB-F1 II, since it needs recapping, I already crank the audio on the speakers up as loud as they can go. I can hear the PSG sound effects just fine, there is simply no FM audio behind it at all. And, on the occasions that the FM Audio does play, it plays at the appropriate sound level. That's why I'm so stumped.

This lack of audio happens on both the original FM-PAC and the newer FM-PAK with line out.

Thanks for this. Just making sure I'm doing this correctly, the command in the original FM-PAC to play BGM music is space bar, right? If so, then it appears it's not playing audio in the BIOS menu either, on either machine.

no, that was an original concern of mine as well. I use the provided FS-A1mkII PSU with the panasonic machine, and the HB-F1 PSU with the sony one. The bricks say they match volts and amps, but I'm always paranoid about the details.

Within the last few moments, the sony machine has seemingly started reliably playing FM music with both the original FMPAC and the new FM-PAK. The panasonic machine still only very infrequently provides output. Using the topic posts above, i can induce a tone using BASIC, it plays back reliably on my hitbit but is silent on my panasonic.

One thing very odd to note, the line-out of the FM PAK I'm using, I can hear the PSG output through it on the panasonic machine. According to the site I bought it from, it should only output FM, no mix. So it's like the audio mixing pin of the cartridge slot is going backwards or something, I'm very confused.

Hi. For this explanation, it seems that this is a power problem.

The FM cartridge consumes more current than the equipment can presumably deliver through the connector. Out of capacitors? On the MSX and / or the FM cartridge? Bad power supply?

You should check these points to be sure what is going wrong.

Good luck