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DEC RA92 Troubleshooting

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spiceminer

Experienced Member
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Dear all!

Any RA92 operators here?

I recently got a few RA92 Drive unit beasts (>30kg each) . All of them have been stored for years in unfavorable conditions, so there is dirt and rust on the enclosure. The drive (HDA) and electronics look almost new.
I can power on the the drive, the POWER OK LED is green and I can issue commands to the OCP.
Whenever i try to spin up the drive, I get an Error E-62 which indicated non readable diagnostic sectors.
From the field service manual, I have found that one can restore them by the T-17 "Read only cylinder formatter".
Unfortunately T-17 only runs when the drive is spun up. Is there a possibility to run the formatter when the drive fails to spin up?

Thanks!

1708896852962.png
 
I had dozens of RA92's back in the day. They were pretty reliable, but occasionally we'd have one fail to spin up after a shutdown. DEC FS would replace the HDA and we'd be good. One time, though, a relatively important disk failed, and there were no RA92 spares in the city. It would take 24 hours to get a new HDA. The DEC FE said that a lot of times, these drives would fail to spin up because the heads would get stuck if they were shut off after running a long time. He allowed as to how you could get it to work again if you gave it a gentle tap to free the heads. It was a story I was familiar with from other types of drives that experienced the same problem. I figured, waddahell, what's to lose, and told him to give it a try. He proceeded to lift it over his head and throw it on the floor. Damned if it didn't spin right up and work until we got spares in and arranged a time to copy if disk to disk. Anyway, I don't recommend that you do it with that much force, but a healthy punch or two, and maybe a twisting motion, might do it some good....if that's the problem.
 
I worked for DEC at this time, but cannot remember any real issues with RA92 in my accounts

On the RP07 (ISS Univac ?) in comparison, I got lots of HDA problems
This was not a hermetic sealed HDA, it was open at the back where the Voicecoil sits
It was extremly delicate to handle, once the spindle lock got removed
If you turn the wrong way, the heads would move on the platters opposite way and damage the surface

On the RA92 I guess there is a spindle lock, so this is no issue
I seem to remember there was a short term fix with new FW to gently vibrate the heads to overcome stiction before startup
Longterm fix was a microscopic grooved structure on the landing zone

So vibration would be the safest method to start with - tapping with a plastic hammer should do it
 
spiceminer said:
Dear all!

Any RA92 operators here?

I recently got a few RA92 Drive unit beasts (>30kg each) . All of them have been stored for years in unfavorable conditions, so there is dirt and rust on the enclosure. The drive (HDA) and electronics look almost new.
Click to expand...

The spindle lock may not be unlocking. Check the manual page 6-20 to see how to bypass.

CW
 
I do have the other four RA92 from that haul and beside that all power supplies are finally broken down I had the same issue before the last of the power supplies gave up ...

In one combination I see the error C6, C7 and E4 and I sometimes get the drive into ready. When I replaced the ECM it went into E-62 which makes sense because the HDA does not belong to the ECM. It seems like that the pattern of this two diag sectors is locally stored on the ECM. Before it throws that error you can hear the heads moving. I think I need to follow the HDA replacement procedure.

Only one of the HDAs has problems with the Heads due to a broken. solenoid. I did open the HDA to check if it could be the heads but they are freely moving when I realized that I do not hear the clicking noise from the solenoid,

Anyway, I will park my work on this drives for now. I need to fix the power supplies first.
 
Thanks a lot for the responses. Sorry I have not been very precise at my initial description.

The HDA motor begins to spin for a few seconds, and I hear noises which I think is the heads moving over the surface. The the motor spins down again and the display gives Error-62 which indicates bad heads or bad diagnostic sectors. If it is the latter, I might reformat them with Test 17. Unfortunately for this procedure the drive needs to be spun up.
 
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