Mention must be made here regarding the cleaning of the keyboard.
This example has been removed from the case prior to a good cleaning of the keyboard.
In this case, chrome cleaner paste and a lot of elbow grease is called for.
A portion of the same keyboard after cleaning.
The preceding pictures are basically to show you what's inside your Stylophone, and unless your own model is showing this sort of dirt or corrosion, it would be best to leave it as it is.
So what are the differences in the circuits?
Well, it's more the components than anything else. As newer, and smaller resistors, diodes, transistors etc. became available, they were incorporated into the board. This makes for fascinating investigation when examining several units, as you can see the progress through the years as the more compact bits and pieces, and more efficient no doubt, (resulting in longer battery life), are used in manufacture.
This is not a hard and fast rule, as components could have been used from a number of different sources, and cannot be relied on, but the photos below show some of the obvious differences:
Black and White model with plain keyboard
Wood Effect model with spacer keyboard
White model with black grill and spacer keyboard
Wood effect model with spacer keyboard**
**This model needs a special mention - see Hong Kong page...
The electronics used to drive these little instruments proved to be very reliable, with the only maintanence usually required being a general clean....