Also, the circuit board is different on my SC-816 than all others ive seen posted so when i take it apart again to tinker with it, Ill take some pics and post them, I used a combination of cn_bryan's and lewismug's techniques.(ground placement from the latter.)

Just successfully performed mod, but also found the issue which made me seek this solution. My tape deck adapter was working fine for about a year, when it one day decided to reverse direction several times then eject the adapter. I dont own another cassette other than the adapter, so I hadnt tested...