Tom,
First, welcome to the WFM site! There are many great folks here with much to share on their experiences with these fine vintage tractors.
If you have the TM1590 technical manual you will find this schematic on page 240-15-5.
Fuse F2 is the 3 amp fuse and it is involved in the TDCM and seat switch interlock circuits, per the following description from the manual:
<font size="-1">When the operator is on the seat and key switch (S1)
is turned to the RUN or START position, current
flows from the positive terminal of battery (G1),
through circuit breaker (F3), to key switch terminal
“B”. The current flows across the switch contacts to
key switch terminal “A”. From terminal “A”, current
flows to fuses (F1 and F2). From fuse (F2), current
flows across the closed contacts of seat switch (S6)
to pin “9” of TDC module connector (X22).
The rest of the theory of operation is found on the page following the schematic where I pulled this quote.
You mentioned that the F2 fuse blows, so look closely at the wiring harness to the seat switch. Since the wires pass under the fender deck and through to the underside of the seat, look for pinched or shorted wires.
Let us know what you find and we can go on from there...good luck!
Chuck