Worth repairing a Velodyne ULD-12 from the 90's?

Your Father sounds like he had it going on, nice.

Market value? Working, its still a potent little model. Without a need for it your on your own.

Not much trouble shooting information in the ULD manual.

http://velodyneacoustics.com/pdf/uld/ULD-12Manual.pdf

George Meyer AV in Los Angeles CA has been and may still be an authorized Velodyne GmbH repair center.

https://www.georgemeyer-av.com

I purchased my first Velodyne subwoofer, a ULD 18 in 1984 replacing a sub from a Southern California Co. who designed a servo circuit with the sensor attached to a driver with minimal modification to the speaker. Velodyne’s David Hall proprietorially designed a driver motor around the servo resulting in faster reaction and loop timing with measurably lower distortion. The difference was not subtle. Still using DD Plus.

With the exception of Velodyne home subwoofer hindsight the down firing cabinet and room location suggestions remain an after thought for the home HiFi community, not so in the recording industry. I ran my ULD on its side atop two old Boogie boards located along the wall positioned within the rooms standing wave mode.

Good luck with it.

@russ69 

"I don't think so, not a fan of down facing subs."

I've found that ugly woofers are more esthetically pleasing when they are down facing.

@sdberman 

"Not working" is a pretty broad description.  As @musicfan2349 suggests, refoam kits are very reasonable and CAN be a DYI project if you have a little patience.  If you have a non-working amp, you can send it off for repairs.  Can't imagine this being north of $200, including shipping. (We fix old stuff.  Not looking for additional work, but just a thought on repair costs). If it's not powering up, you might look for a blown fuse?

Sentimental value?  Who can forget "It's so fine, my VEL-O-DYNE?"

Probably not and besides, most all the new subs come with an app that makes setup a breeze.

All the best.

@waytoomuchstuff You mean that multi-purpose spray cleaner or a big block Chevy...?

there is a place in new jersey that fixed my servo board on my uld 18mk2.

https://www.ebcelectronics.com/