I also have Inspiron 1545 and want to get new adapter. But having same doubt about you. It seems that octagonal design was for limited period / models only. And such adapters are rare to find/ costs too much. The round plug adapters are easily available in market. and some have mentioned that they work well with octagonal socket. On the other side, i also read one post mentioning that round plug remains loose and had damaged the DC jack. So again i am confused.
Plz let us know if you tried round plug adapter with 1545.
I have heard that you have a dell inspiron 1545?
On some models, as we have already established, it has a octagonal AC adaptor.
I also have a Dell Inspiron 1545 sat in the back of my shop.
I have tried the round 7.5mm plug and it seems to be fine. I have wiggled it about a little bit and it still seems fine.
After about 10 minutes of vigurous wobbling of the cord, it still seemed fine.
~15 minutes later i went to have aother go at wobbling it vigurously and it seemed to have made the AC jack come loose.
I have re-souldered and it seems fine.
I have tried it on a different 1545 with the ocagonal adaptor and had the same results in abouth the same amount of time.
The moral of the post,: Dont wobble any adaptor in the jack for 25 minutes!
Thanks, Ben (Founder and C.E.O of Tornado tech