No sound in game on modded TMNT Arcade 1Up Cabinet

[77claws]

Pi Model or other hardware: 2B
Power Supply used: (If using a Pi): CanaKit 5V 2.5A
RetroPie Version Used (eg 3.6, 3.8.1, 4.1 - do not write latest): 4.3
USB Devices connected: just the controllers listed next
Controller used: 4 EG Starts Arcade Joysticks w/Buttons; usb nes/snes controllers; usb pc gamepad

PROBLEM DESCRIPTION: Hello! After modding a 4-player TMNT Arcade 1Up cabinet that uses small Pyle 3.5 inch car speakers in conjunction with a Kinter MA170 amplifier, I have discovered that there is no audio during gameplay. There is audio on the startup video of Retropie and on the screensaver (which cycles through random games) but no sound at all in game. Also, in the days and weeks before I attached my raspberry pi to the modded cabinet, I would hook it directly to my 4K Samsung tv via hdmi to play it on the big screen. Sound and video worked amazing, so I'm guessing this is a simple setting to push the audio out through the car speakers. I 've researched a bit and know there's probably a config setting that needs editing, but I'm not sure how to access it or what changes to make. When inserting the microsd card into my Windows 10 laptop, I have limited access to the card, but I did edit one of the config files there, changing the HDMI line from a 2 to a 1. This did not help. Thanks in advance for any help you can offer.

[mitu]

@77claws Have you tried configuring the sound output from the Audio menu in RetroPie ? Choose the Headphones jack as the default sound output and it should route all audio over the 3.5mm jack.