if you are doing it for free while being forced to pay for your buddy's new ps2 v13, i wouldn't call him a friend...
anyway, check fuses...especially 3.3v power point; whose smd fuses are heat sensitive, so you could have fried it while doing it as your 2nd attempt on new ps2 failed with the same result
when you removed mod chip, did you removed all the wires, too? floating wires can cause a problem, too.
i also did with 760 on v16, and it worked well
Ref +: psaras, marcus21, sirusxXx, gamecubesuxs