Bringing an Bontempi Organ Back to Life

I wanted to bring an old charity shop Bontempi organ back to life. Given that there was no mains adapter, I built a solar power rechargeable DIY battery bank. I then played it through my amp/pre amp. I think that the organ is about 50-60 years old, and thus far, I cannot find any more information about it. This is very much a proof of concept, and I wonder if I could use the POC to build a robust unit and sell it - comments much appreciated.

1. Old organ
2. Solar panel
3. Rechargeable batteries
4. Amp/pre-amp and leads
5. Electric connector
6. Multimeter / ammeter

I used a batch of rechargeable AA batteries, linked to a solar panel, which would provide a voltage between 7.5 to 9 volts - and thereby obviating the need to cntinuously replace internal batteries. I used an ammeter to verify the voltage. I learned that lower voltages powered the unit but it cut out. I used a connector to connect the batteries to the organ.

Luckily, the connector was a standard amp-lead. However, when I connected the organ to the amp it didn't work. I therefore had to use a pre-amp whereby I connected the organ into the input of the pre-amp, and in turn, used another lead to connect the output of the pre-amp to the main amp input jack. This is the same arrangement for most microphones.

Despite a bit of feedback, I was able to play the organ through the main amp to quite a high volume ( see the video)

1. Vary the pitch of the organ and play it through a loop pedal to check the different sounds I can obtain.
2. Combine the media files from 1) with my guitar media files. I'm hoping for an old Beatles Hammond Organ sound.