RK05 Help

[Tony Duell]

> 
>  Well, as Tony surmised, the blower motor itself was bad.  The odd part
> is that there were two RK05's in the system, and both of the blower motors
> were toast.  I'm wondering if there was something environmental about the
> storage (dry, insulated/sheetrocked garage, but no heat) that did something

The insulation on those motors is not brilliant to say the least.  We have 
particular problems over here, because it has to stand 240V -- the motoe 
may only have 120V between the ends of its windings, but there's 240V 
bwetween one end and chassis ground when the drive is set for 240V mains. 
I've had the darn things catch fire.

Do you have a megger? If so, I'd stick it on the dead motors (windings to 
frame) and see what happens.

> to the motors that caused them to die in both drives.  I took the blower
> motor
> from the parts drive, and it was fine.  It was made by a different
> manufacturer,
> and seemed much more robust.  I now have one drive that will work.
> I'm hoping that I can, with the procedure Tony mentioned for tearing
> the motors down, perhaps cobble together another motor, or perhaps take
> the motor to a motor repair place and see if the windings can be repaired.

The bad news is that the stator laminations are spot-welded into the 
case, and only one end plate is removeable. Rewinding that would be an 
'interesting' project, therefore.

> 
>  It's interesting that in order to remove the blower motor, you have
> to destroy the foam seal that seals the motor to the electronics bay, in
> order
> to get to the fourth allen head cap screw that secures the motor to the
> drive

I seem to rememeber there is a way to get a tool onto that screw, maybe 
you need a ball-ended allen key or something, which can be used at an 
angle. Or maybe you can just push a normal key past the foam, and if the 
latter is in good condition (which it won't be now), it'll just deform 
out of the way.

> base.  I have to improvise and make my own new foam filter I put the good
> motor back in the drive.

FWIW, taht foam seal is not essential by any means. I've run plenty of 
drives without it.

> 
>   The 2nd drive, as it turns out, also had the upper head crashed at some
> point in time, it has a lot of oxide on it, and shows signs of getting hot,
> so to get
> that 2nd drive running (once the blower motor issue is resolved), I'll

You may have to replace it, it may just need a really good clean (I've 
heard that even quite badly mangled heads will clean up anf fly again).

> have to replace the top head.  My question now is, do the heads have
> to be replaced in sets, or can one head be replaced?  Once a head is

You can replace a single head. Of ocurse you replace the assembly (head, 
spring leaf, mounting block), but you don't need to replace the other 
head as well.

> replaced,
> does the drive have to be aligned in any way?  I've read the head

Yes. In fact if you remove a head you need to do the alignment even if 
you put the same head back in again.

> replacement
> procedure, and it suggests it, but I don't have an RK05 alignment pack,
> which
> pretty much precludes doing that. Is there a chance that just replacing the
> head, being careful to make sure it is properly seated and that the torque
> on the holddown set screws is correct, that the drive will "just work"?

It'll work, but you won't be able to use the packs in any other drive, or 
vice versa (this is, of course, an 'interchangeability adjustment' -- a 
drive with misaligned heads will read its own packs).

There are 2 screws for each head. One clamps the head tail into the 
positioner carriage. The other forces the head forwards as you screw it 
in. The procedure is to loosen the first one, back out the second one, 
push the head as far into the positioner as you can, then with the 
alignment pack loaded, slowly screw in the second one until the head is 
aligned. Clamp up the first one, then back out the second one a bit 
(it'll have no effect), to prevent it moving the head later due to 
thermal expansion, etv.

Therefore, if you then remove the head you haven't a hope of getting it 
back in the right place without an alignment pack.

> I have a good set of heads from the 'scrap' drive.
> 
>  By the way, an RK05 drive will indeed load the heads, go READY and give
> "ON CYL" status with no controller connected, so long as the terminator
> is installed in the last slot of the electronics backplane in the drive, and
> a good cartridge is installed.

Thought so. By 'good cartridge', all the drive checks for is the sector 
pulses from the hub notches. It doesn't matter whart's on the disk 
(there's no servo, or clcok track, or anything like that).

-tony