Bentley electric piano has very short note sound?

I have an old (20 plus years) electric piano made by Bentley Pianos in Gloucestershire. It's in a mahogany case, 5 octave keyboard, 2 pedals and 3 switches to allow for piano, organ or harpsichord sounds.
The problem with it is that the sound made when pressing a key is very brief, even when holding the key down – it just disappears too quickly. Even using the right pedal (sustain?) doesn’t help a great deal.
My question is – is this just a function of it being old technology – were all electric pianos like this from decades ago? or is there something that could be repaired or improved? It’s very frustrating to play even though I’m very much a learner.