How can we isolate the H1 on wd400eb, the internal format passes on the pc3k but when we go for logical scan it gives error, it seems that H1 is having problem.

Hi,
If you want to fix the drive use, is one situation.
If you need to do the recover, is another situation.
If you need to do the recover, the best thing is - to change the heads.
But in Western Digital drivers, the most important thing is : you need a good diagnostic.
If you do not have a good diagnostic, you can not do much with theses disks.
Any way seams to me that you have the PC3K, and if you have you know how to perform a good diagnostic.
Has new manuals for the new version of the WD utility, and I think that can be a good ideia, if you can take a look in it.
The biggest problem in the WD, seams to me that is the defects lists, and this can afect the translator, and when this
happens, sometimes not often we have a situation that looks like a disk with heads problems.
So the best to do is do a diagnostic in PC3K.