Sick RL11 controller help

[User Staylor]

I have a PDP-11/34a UNIBUS system, and the RL11 controller just died on me.
I haven't a spare RL11 to diagnose it with, so I've been toggling in whatever
test programs I can find.

The RL02 drives I have, the cables and the packs are all verified good by
booting and testing them on an 11/53 system.

The symptoms are as follows:
o	No drive will boot.  CPU halts.
o	Using vtserver, I can copy the first 8 blocks from any drive back to the
	vtserver host, but then fails on block 8 with HNF (Header Not Found) in
	the CSR.  Always block 8 (blocks 0 thru 7 always read fine).
o	A toggle-in oscillating head positioner test code (from the manuals) seems
	to audibly indicate the head carriage is moving back-and-forth continuously.
o	The machine seems otherwise unaffected.  I can toggle in and test basic
	machine functionality for memory, CPU, interrupts, etc.

It seems quite certain that I have a RL11 controller that has stopped working properly.
Not having any other UNIBUS disk systems or any way to boot XXDP, I can't do any further
testing.

The machine and disk were working fine, and I was even running diagnostics on it when the
failure occured.  

My question is this:  Is such a sector addressing failure at all common enough that
someone could suggest replacing one or more components on the RL11 controller before
I try to obtain a replacement and chuck this one into the trash?

Perhaps someone has a working controller they could sell?

Thanks in advance,
-scott
staylor (at) smedley (dot) mrynet (dot) com