Topcon IC-1 auto... Shutter issue?

I purchased a Topcon IC-1 auto, in working order a couple of months ago. However, on inspection the shutter only fired at one speed, ahhhh right the shutter will only work with a battery fitted. I fitted a battery , the exposure meter worked but the shutter still only operated at one speed. I contacted the seller and he refunded the money and said keep it.

In working order they are said to be very nice cameras and the lenses are said to be very sharp. So....I don't want to junk it if I can save it. There is some corrosion in the battery chamber which I cleaned as much as I can and still only one shutter speed. To see if it's saveable I need to remove the top cover in order to see if there are any broken wires or more extensive corrosion, usually straight forward however I can't figure out how to remove the winder or shutter button has anyone got any suggestions?

If it's not the battery its likely the electronics that control the shutter. IC stood for integrated circuit and unlike the early auto 100 it has a focal plan shutter rather than a leaf shutter, but shares the UV lens mount. I have the leaf shutter version the 100, the lens quality is quite good, and it will work in manual mode as well as shutter speed preferred auto exposure.

If one can be sourced, you should be able to have someone replace the defective IC.

By the way the 50mm is a 6 element in 4 groups, the cameras of the same time period that were competitors like Kowa and Petri had 5 elements, I think the Topcon was sharper at F2.