Source: http://www.radiomods.co.nz/kenwood/kenwoodts870.html
From: Howard Ryder - W4NTW@ix.netcom.com
This mod will enable the TS-870S to transmit on the full 40m band and other frequencies such as 60m.Remove top and bottom covers.
1.Remove the top screw from each side of the front panel assembly. 2.Carefully rotate the front panel forward to gain access to the control board(x53-3560-11 a/4). This board is mounted vertically against the body of the transceiver. It is not the board that is mounted in the front panel assembly. 3.Locate and remove resistor R244 from the control board. R244 is below IC12 ROM and above IC23. There are two chip resistors, one on top of the other -carefully remove or break the top one..it is easily fractured -that's R244. 4.5. Reassemble and then perform the cpu reset by holding the A=B button depressed as power is turned on. Note from Barry GM3YEH: It is very easy to remove R244 by simply placing a solder iron tip across both ends of R244 (1 kΩ) at the same time. This melts the solder on both PCB pads simultaneously and the resistor falls off the board. This is better than mechanically breaking the resistor off the board which is likely to damage the pads on the board.
Top and bottom covers removed and front panel folded down. R244 circled in yellow.
Close-up view of R244.
R244 removed.