JTAG novice here...
Just built an NKC Electronics JTAG board; mega16-based clone, it says.
I wired up a cable to connect it to the ETT mega128 "stamp" (futurlec.com). Check, rechecked, ohmed out, buzzed wires. All seems correct. Port F pins on the mega128. JTAG board power is coming from the 5V of the target board. The target board works fine for ISP and serial bootloading and running the application. SPI is wired up but I understand that the mega128's JTAG is independent of the SPI.
AVRstudio says it sees the JTAG device on COM1. But it says it cannot see the target device.
I've used my Atmel ISP to ensure that the fuses for JTAG and OCD are enabled (they were).
I have no other JTAG target devices to try but have ordered one. Until then, any ideas on what I may be doing wrong?