So I bought a modem from DreamcastLive with a built-in DC-DC booster board back several months ago and just got around to testing it yesterday, sadly to no avail. After doing some testing, it seems like when it has one light on (no dialtone/command sent) it outputs a proper 12 volts to the phone line, but when both lights come on (modem is initiated), it drops down to 5 volts. This is enough to hear it over a normal telephone and in fact if a number is dialed with a normal phone while it's connected to DreamPi, it will connect and do all the nice modem sounds, but it doesn't seem like it's able to power my Model B modem. I've tried several different cables and configurations (swapping out a Pi Zero W for a Pi 3B, etc), but I just can't get it to work. I'm assuming it's a voltage issue as several people have said the DC modem won't operate on less than 9 volts (for NTSC modems), but I also am unsure about what the actual minimum voltage is considering batteries' voltage drops as it loses charge, and people seem to get quite a lot of time out of their line voltage inducers. I'm assuming the issue is either the DreamLive modem's output voltage or my Dreamcast modem, and I'm not totally sure which I can safely determine.
The DC-DC board DOES still output 12 volts even whenever the voltage on the phone line drops to 5 volts, so I'm definitely not sure what's causing the drop, unless perhaps the board could be wired a different way. Any and all help would be greatly appreciated.
Thanks!