Fanfarikuss

Dear community. I own a MZ-RH1 HiMD Portable which was stored for a few years. Due a "nostalgic attack" and because there are so much stunning live recordings, I'd like to run the device again. First: The LIP - battery was dead, but I fixed it with a after market one. But the main problem is, the cable remote control doesnt work. Checking the line out jack and connecting the earphone directly with the device, I can hear music, but I'm noch able to change settings of sound without the remote. First I thought the remote control itselves is dead, but I tried it with another Sony portable, everything worked well. So I believe that the 4 contact jack besides the stereo jack is not working. I just cleaned the contact surfaces, but without success. Can anyone name the special Sony standard Line Out jack? I googled the whole world and nerly got crazy, but all I found was Line Out Jack. I'm sure that it is possible to solder in a new one, but first I have to know the correct name for it. Please help.