I bought a Camera on a Flea Market. It was a Fujica GEr. At home I realised that it got the typical Mercury Battery Problem. It required two PC640 Mercury Bateries they are out of production for years now. So I decided to built an adapter. The Batteryspace fits four Euro-cents and a 675 Zink-Air ( Hearing Aid )Battery. So I build a housing for it, out of one cent and some Sugru for each battery .In combination with the three other cents it replaces the PC640. So you need eight cents and a litle bit sugru. With the Hearing Aid Batteries you got the same Voltage as the camera requies. See my Pictures for Details.
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