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DEC RA81 Drive

U

User78

Experienced Member
Joined
Jul 24, 2015
Messages
69
Location
Germany
Hi All,

I have picked up a RA81 last weekend, and have managed to get in to the 2nd floor. Really heavy!
Until now I have checked the Voltages, removed the Foam Filters, unlocked the drive and turned it on.

It's my first RA, and I have no idea which noise and sound this drive should produce ... but for me it sounds like the ball bearings are not OK.

So feel free to listen: https://www.youtube.com/watch?v=2sV3k5-Zge0

Any suggestions?


Many Greetings
Ulrich
 
As I recall, the RA81 was never very reliable, so I wouldn't expend much effort to resuscitate it.

On the other hand, I built a cart to move stuff into my basement. Here is a 750 making the journey
IMG_20151129_103752.jpg
IMG_20151129_104033.jpg
IMG_20160101_133044.jpg
 
Anyone who would go thru that much trouble to move something into their basement, all I have to say is “you the man”. When we moved into our new house I had the two car attached garage divided and finished off for a work shop at grade level with concrete floor just so I can wheel racks of stuff in and out to the detached garage. In our old place I had a workshop in the house and always worried about things like floor loading.
The biggest issue I think that I would have with the basement workshop is that someday that stuff got to come out and gravity is not your friend at that point.
 
I had the plan, to build an goods lift, but our german authorities have not approved them.
So no way. In general I have managed to lift all my stuff with the help of my Wife, so no need by now. ;-)


And now back to the topic.

I know that the reliability was not the best, but my drive seams to be in good condition. I have attached a VT420 to the drive diagnostics Terminal port (300baud, 8,n,1).
The drive passes all tests, so that I would like to use them.

So the question is: Is it save to use it, or should I be scared about the noises of the drive? Maybe this sound is normal.....

Many Greetings
Ulrich
 
I have the RA82 which is basically the same drive but a higher capacity. Mine will randomly halt with spin errors (again, they're all not all that reliable...) but once your drive goes to READY it should be ready to go. I don't remember if it's just the RA82, but spinning the drive up with Write protect and both the A and B buttons not selected should put the drive into self-test after 30 seconds or so of being spun up. The drive will THEN make a lot of noises as it does various checks of itself.
If you have a UDA50 and the cabling, go for it, otherwise you will require a UDA50 controller and you will need to build your own cables. (it IS possible. I have documented it on this very forum)

I do not have audio at work but the HDA assembly has a static brush assembly on the top of the sealed unit. It's removable with a pair of snap ring pliers if I can recall from the service papers. That can be a source of some noise. Also verify that all your front panel bulbs are good. Pressing the FAULT lamp should lamp test everything, including the FAULT lamp itself. I think they were #86 bulbs.
 
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There were to HDAs for the RA80 & RA81. The originals are painted a greyish tan had a very high failure rate. The new HDAs are black. We have seen lots of spindle sensor failures, so that might explain the spin errors.
 
Qbus said:
Anyone who would go thru that much trouble to move something into their basement, all I have to say is “you the man”.
Click to expand...
Years ago, I gave a friend of mine a PDP-11/70 (he wanted to create a mega-BBS). It was in the DECdatasystem 570 (VAX 780-style) doublewide-plus cabinet. We unracked all of the innards and then numbered every piece of the frame, drilled out all of the rivets and painstakingly carried it all down the shaky narrow steps to his basement and re-assembled it using nuts and bolts. It actually worked after all of that! I lost track of him some years later, but even if he sold the house, I expect the 11/70 is still down there in the basement. :)
 
I have besides this thread contacted Henk Gooijen via Mail.
He has also the impression that my drive makes too much noise.

So the hint was now to remove the drive belt and turn the drive by hand, to test if the bearings in the Drive are bad.

I keep you updated.

Ulrich
 
Hi All,

I had a deeper look onto the HDA of the RA81, and have recognized that my drive looks quite different than it is shown on page 2-21 in EK-0RA81-SV-001_Svc_Oct82.pdf.

The whole brush ground spring is a massive plate with long screws. And for me it looks like they hold something in the drive and not only the small ground spring.

So seams to be my drive revision is different to the described one.

Any hint? Or someone with knowledge about this?

By the way, there are a huge amount of very small copper chips around the grounding spring. In detail they are from exactly this plate and it looks like the spindle has started to burn thrue the plate.
Maybe this is the reason for the strange noises from the drive.


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Many Greetings
Ulrich
 
Have you tried connecting a serial terminal to the diagnostic port, and then running some of the tests?
I have one of the special hand-held terminals described in the manual.
 
I have successfully used drives with bearings that were more noisy. I would run the drive for a few hours and see if the noise gets better or worse.
 
After seeing the grounding spring, I started to think about it is the reason for the high frequency sound.

The spindle end is mostly gone through the grounding spring, and I have all over the plate small copper particles.
So I think I need to rework the grounding first, but my drives version differs in this fact from the documentation.

I have loosened the grounding screws a bit, but it feels like they hold something in the drive, so I have fastened them again, to prevent damaging something.
 
I know on smaller 5.25" drives if the grounding brush begins to squeal it's as easy as carefully sanding the pad down a little, so you could investigate that route. I would regardless however clean the brush area out.
 
Hi all,

the loud and high frequency noise was coming from the grounding spring.Nevertheless my RA81 HDA looks quite different compared to the pictured one in the available documentation.

I have now removed the grounding spring, drilled a new cavity for the spindle in the pedestal bearing and cleaned them.

Now the noise has reduced dramatically. The drive is attached to the MicroVAX II and boots VMS 5.5-1.

It's a real hard disk, and it makes me happy to see them working again.

Many Greetings
Ulrich
 
Hello,
I have a VAX 730 including a RM80 disk (similar to RA80, with same HDA I think).
Unfortunately the HDA is of the grayish kind...

I'm in search of a working replacement HDA for it, or maybe also an RA80, or even an RA81..
Ulrich, where did you find your drive? Maybe they have another available?

Thanks
Andrea
 
Hi Andrea,

depending on your location ebay.com (Item 370509699659) could be interesting. There were also some other NOS RA81 HDA available over the last months.
I have only this one, and search for at least three additional drives, which I would like to use with my other VAX/PDP systems.
There are also some more differences, like at least 16/18 bit versions, ... .

Cheers!
Ulrich
 
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