There are 4 possible TCD cells for the 6890 GC.
For all instruments after serial # US 00009084 (or DE00003936 and all CHxxxxxxxx) -about Oct. 1997; use Type 2 cells.
These are either; G1532-60685 for most "normal" applications
or
G1532-60695 - specially passivated TC Cell for organic acid analysis.
For earlier 6890 instruments (prior to the above serial # breaks), the instruments could need Type 1* cells;
either G1532-60675 for most applications
or
G1532-60690 - specially passivated TC Cell for organic acid analysis.
"Type 2" TC cells can be identified by the 1/8 inch tubing gas connection mounted directly on the back of the GC.
"Type 1" TC cells can be identified by having the 1/8 inch gas tubing pass through the back panel of the GC (the connection is inside the panel).
* Please note that original "Type 1" cell instruments might have been updated to "Type 2" cells, so the serial number break may be misleading.