It's typical when you have the IIfx ROM but not the IIsi. I know because I have both ROMs and have tested both extensively. I have also mentioned this in the past:

viewtopic.php?p=81070#p81070

Even so, if your logic board still has the original capacitors, they really do need to be replaced. I bought two sets of replacement caps from our very own "trag" in the past, for a great price:

viewtopic.php?f=4&t=4884&hilit=trag+capacitors