Sound like you have Jurassic Park AC-3 THX which will require a demodulator to play AC-3 Laserdisc. Grab a non AC-3 Laserdisc off eBay and I bet you will be able to play that.
Sony VPL-VW285ES Projector / Denon AVR-X6500H Receiver / Aircom T10 Cooling Fan
Sony BDP-S790 3D/Blu-Ray / Sony UBP-X700 4K UHD
Pioneer DVL-909 Laserdisc / Lexicon LDD-1 Demodulator
Samsung DVD-VR375 DVD/VHS