Whe I worked with a Hammond Tech in NJ we would get calls about organs like this. People spent some serious $$ back in the day on them and all we could say was we could help them take it to the curb. Not to be mean but we then explained its like an old computer or TV, basically worthless and not worth or maybe not possible to fix.
Its the fact its a big piece of furniture that I think holds them to the idea it has value. Same with old pianos. " But it was Mom's" Yea, and now its a 50 year old spinit thats good for an anchor.
Even Tonewheel Hammonds ar losing value with all the new clones out there. Times change.