This question begs to be asked
What is it that makes WD drive heads any different from other drives

Before you say the head axis is affixed with a screw through the lid,
let's take a second look. As far as I can recall, every drive I have ever
opened had a screw through the lid to the head axis.

I think maybe we have been looking at the problem all wrong.

It seems very illogical that the heads would or could be aligned
during manufacture AFTER the lid was installed. So that would make
one think they had to be aligned BEFORE the lid was installed.

SO, what are we missing? What is the real answer to aligning these heads?
Why are they different from other brands?

The issue is that the heads aren't aligned at all in the factory. They are simply placed in, and once the drive is assembled, the servo tracks are then written. The difference between WD and everyone else is that other drives screw the heads in firmly, then the lid goes on. If you open a WD drive, you will see you could just lift the head stack out. Worse, it's put on a post that is a bit smaller in diameter than the hole in the head stack's bearings. Because of the sloppy fit, the head stack can be in any number of positions, and that position is lost when you remove the cover.

Well, I was under the impression that the drives were somehow servo-written after assembly but before the PCB was installed. But I would love to hear what others say.

The WD have controll connector footprints on the back side of the pcb.
So, it is possyble, the servo/sa writing AFTER complete assembly.

Janos

So any of your pros have a tip for aligning heads on denser drivers after disassembly?

Also, my statement above didn't intend to address anything about the PCB, just the heads.

Unfortunately no.
I am reading this topic, because i am interested about alignment too.
At this time, i have no good solution for this problem.

Anyway, i have tried some times, to opening the donor drive, make a little move on the mha, and close again, and start.
But a lot of times, the drive can recalibrate adn reach readyness!
But after i have made the HE, only the clicking comes.....

I think this caused by some different of the mha itself.
Like different level of the bearing or something like this....

Janos

So, the alignment we are looking for is the misalignment of the servo
tracks????

Not exactly.
We are looking for the right alignment of the mha for the servo, and the general unaligned state also.

Regards,
Janos

I just examined a couple of drives
one had a screw through the bottom of the case
and the other didn't ..and I could have sworn
that I have seen wd's which screwed to a post
on the case..
I always thought that the hole in the head assembly
close to the axle was for the servo-writer, but if they
are written with the lid on, then that hole is unreachable
from the slot under the case.

Stw is done via pushpin stwriter from backside and with pcb off after the lid is closed. And we are missing something because... (think! Pros interested only, pm me.)

As we are all still looking for a solution to this I had an Idea.
(Don't think I'm crazy, it's just an Idea at this point)
First off going back Many many years before hard drives
were available, back in the days of 5 1/4 floppies. I had a special
floppy disk that had signals imbedded on it, and special software
that would read this signal and display a graph on the screen
as the heads were adjusted, the display would change until you
had the heads properly adjusted.
Now let's think modern times. Actionfront (aka seagate recovery)
has a tool called signal-trace (which we haven't heard anything
about in sometime). Couldn't something like signal-trace be used
to hold the heads over a track, then read the servo-marks from
each individual head and then adjust the headstack until each
head was syncronized to the servo-marks?
The software portion would of course have to display the signal
of each head simultaniously.

Of course we would also need an adjustment mechanism
(which I know a few are working on )

Any thoughts?

I think this a is a good idea, but WD don't have the serial bus like seagates drivers ?
I have not studied ATA commands but I don't think there are documented command to help such project. Where you thinking connecting directly to the heads by bypassing PCB ?

If using ATA commands only this is something I'll try to program, it's better than my glue idea.

Do a google search of signal-trace
it is a hardware/software system developed by actionfront DR
they were bought out by seagate .. the original Signal-trace
was done on western-digital drives, but was supposed to be
drive independent.
I think the whitepaper is still available on the actionfront website

Interesting read, but bypassing PCB is not possible anymore. However what about doing picking between head connector and PCB ? This would need high resolution sampling rate. This could allow to read "expected calibration sequence" on a good drive and compare it to a non-aligned drive.

Not possible. Shorter: I have found and made a solution - after a long time, spent a lot of money and involving hi-tech - definitely NOT for common people. That's why WD DR is so expensive. Other people have found other working solutions as well, either complicated. And NO, I won't share.

Why is bypassing PCB not possible?
we're not talking about accessing user data at this point
(which is what signal trace did)
only talking about controlling the motor/voice coil/read channel.
then the only thing that needs to be accomplished is seek to a
servo-mark with head 0, then read the signal on each head,
and compare/adjust till signals match.

Are you going to sell this solution?
or can I send you all the wd's I get in that need headstack replacement?

Almost surely not. I never thought about being an outsource for other DR, though. Maybe I should explore this possibility.