My external flash, a Minolta 3500xi, doesn't seem to be synchronized with my camera Sony A 200. Can you help?
I don't think this flash is compatible with your camera in auto mode — forum posts seem to confirm this, and this blog post goes into greater detail. In short, you can use it as a manual flash, either at full power or at ¼ power (with the "Lo" button), but can't get further automation (or wireless optical control).
The flash has a guide number of 35 meters when zoomed all the way in to its 105mm setting — this corresponds to a lens of about 70mm on your α200, since those numbers are given for a 35mm film camera frame. At the 50mm zoom setting, it's GN 29m, and at the widest 28mm setting it's GN 22m (again, that's a decently-wide ~18mm on your camera, so the flash's zoom range pairs nicely with the 18-70mm kit lens). The Lo button will halve the effective GN, which gives you a bit of flexibility.