TASCAM 688 MONITOR B PCB 52101678-01 this is due to TEAC

this is due to TEAC using a cheap alloy thats commonly used ( I kid you not) to make tin toy soldiers etc

good panel this and was only one in the unit

This is rare and gets broken I have not found a source of the sensors

and G16S) this one though has a longer capstan for the 1 inch tape

TASCAM 688 MONITOR B PCB 52101678-01 this is due to TEACBoard from a 688 and maybe common in some others The 688 was really the flagship analogue portastudio amazing what the could get on 1 8 inch tape I was amazed how heavy and how big the machine was must be 15 kilos maybe, Nearly all the boards inside are with connectors so its one that can be serviced easier I have seen 2 versions of this pcb