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RA82 spinup troubles

NeXT

NeXT

Veteran Member
Joined
Oct 22, 2008
Messages
8,149
Location
Kamloops, BC, Canada
So I located a circuit in the house which is used the least and plugged the drive in. Flipped the breaker and was greeted by fans spinning up and no nasty noises or magic smoke. Good. :)
Next I took a piece of wire and jumpered the 6 o-clock and 9 o-clock pins together in the SEQ IN port so it would be allowed to spin up, unlocked the heads, and started the spinup.
The lights in the house dimmed, the motor and drive started to spin up, but then it kicks out and lights the fault lamp.
Hmm, okay. So either something is wrong or the motor is overloading. I'm not quite sure.
Tried two more times, same deal.
I checked waht a single fault light meant according to this and there is nothing attributed to just the fault lamp. I can't check the bulbs either. I don't know how to remove them.
Huh. Bizarre, and worrying. :/
 
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I suppose the first thing that could help us is if you took a video with sound, with the hood up of the spinup process. Start with the fans running, before pressing run. Then announce and press run, let us hear the sounds, and in particular how long the motor runs until the fault comes. That delay time can be helpful in determining the problem.

There is a belt that runs from the motor to the HDA. Does the disk indeed start to spin up? That belt can be tensioned and maybe the tension needs to be adjusted (belt slipping and disk not coming up to speed fast enough). Belt adjustment is covered in the RA81 service manual on bitsavers. I'm pretty sure that this is the same across RA80/82/82.

Also, the disk motor is a capacitor start motor. In the RA80, the capacitor was not switched by a mechanical centrifugal switch (as with most machine tool motors), it was controlled by the drive controller. Ultimately, the spin-up problem in my RA80 was a bad output pin on an I/O expander that drove the drivers that closed the start capacitor relay. I highly doubt that anyone else would have this problem, but I just mention the capacitor start so that you know to listen for the start capacitor relay to cut out.

The RA82 should have some pretty advanced diagnostics. The RA80 has on board lights and switches and EXTENSIVE interactive on-board diagnostics. ISTR that RA81 and RA82 have a port to connect a 300 baud RS232 terminal so that you can interact with the drive controller directly. The DB25 connector may be up by the motor start capacitor on the right side of the controller when facing the drive from the front.

Get the RA81 service manual (EK-0RA81-SV-001) from bitsavers and look at chapter 4.

The manual will also tell you how to service the lamps. I use needle nose pliers to carefully grab the glass envelope and slide them out, but I think the right tool is actually a piece of rubber tubing. Jameco still sells the bulbs.

Lou
 
I gave up trying to get my RA82 to do anything. I couldn't even get anything from the diagnostic serial port. It would be nice to see it spin up and in operation at least once, but the reality is even if it worked I probably would almost never use it.

If you can't get anywhere getting your RA82 up and running you might have an easier time getting your 11/84 UDA50 up and running with an RA70. I'll have to see if I have any working RA70 drives I could spare. I connected one to a 4000-700A and spun it up last night just for fun.

-Glen
 
I wish I lived a little closer to you guys to help you out with the troubleshooting / repairs of your drives. I really enjoy the repair aspect. Most of what I get is broken and so since my expectations are low to start with, I'm usually not disappointed.

Glenn, if very little is working, I would suspect a power supply problem on your RA8x drive.

All that said, the RA7x drives are compact and seem pretty reliable. I have an RA72 on an 11/73 that works fine.

Lou
 
Because of no sound insulation, I can't run the drive when I get home from work because by then it's quite late.
I'll try and get the video up this afternoon after the laundry has finished.
I'm hopeful that the this isn't too big of an issue as it seems like the drive was very recently pulled out of active service and has not even had a month yet to sit in storage. I'm assuming it's just very cranky.
 
The video just got thrown up on Youtube.

http://www.youtube.com/watch?v=bHVtAbxZ-7w

I'm hoping you can hear the motor trying to spin up. I can't use my microphone as my roommates seem to always be either watching TV, doing stuff on youtube, or playing music all day long.
Anyways, that aside, here you go for a quick in-a-nutshell video.
 
I did not hear the telltale sounds of a disk spinning up. It's a very distinctive sound, as I had an RA80 (or was it an RA81)
that Lou now has. It might normally take 20 seconds or so to fully come up to speed, so the fault light going on after just
a few seconds implies something is wrong. I don't know enough about these old drives to say much more. Hopefully it might
be a slipping belt like someone suggested.
 
It looks like the brake disengages and the motor starts to spin. However, it doesn't spin for long at all. Nowhere near long enough to get up to operating speed.

My first thought is that the sector pickup is dirty or has some problem. It would be the first indication to the drive that the disk is not spinning when it should be.

However, let's not get ahead of ourselves. Get the RA81 service manual off bitsavers, and start learning how to be more interactive with the diagnostic port. I may start doing that myself this evening.

Lou
 
They have a manual specifically for the RA82. It looks like if the system is not seeing the disc spinning, either the speed transducer is acting up or the cabling to it is.
Also, what would be the signs of the brake not fully disengaging? It's possible that since it's of the friction variety it might be still on and it's overloading the motor.
 
I finished repairing a broken power switch on a VT-100 I grabbed from the office last night and set to work this morning figuring out what was going on.

100_1625.jpg


The thing just smells like the 80's. It's wafting out of the vents in the top. :D

Anyways, I got into the diagnostics console using 300, 8, n, 1 and then fired off a RUN DAIG command.

100_1626.jpg


My assumption is that 00 means it passed so that's good. Then I checked to see if there were any silent faults.

100_1628.jpg


Nope, nothing there either. Clean as a whistle.
I then pressed the RUN/STOP button and let it do its thing, then ran the diagnostics again which passed but then when I checked for any other faults...

100_1629.jpg


Aha! According to the RA81 service manual (there was no RA82 service manual available on bitsavers) a 01 fault code stands for a "Spindle Motor Speed Transducer Timeout" so we are in the right neighborhood.
Though from there I can't determine if it's simply not responding when the drive starts or if it's not giving the computer the data it needs to continue the spinup.
I'm hoping the speed transducer hangs out underneath and outside of the HDA assembly. Regardless, inspection of it means totally unbolting and removing the HDA.

Edit: According to the manual, the transducer is an optical sensor that is triggered depending on weather or not it's passing through a hole in the timing disc, which is luckily located outside the sealed HDA. Might the LED have just died or would that not be giving a totally different error code? (03 - spindle not accelerating during startup)
 
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Man, I love this thread. You gotta love that 80's smell. My 11/73 is in a pedistal mount BA23 case, and every time I sit in front of it (beside it actually) and turn it on, I get a blast of that 80s smell. That machine has smelled like that for the 10 years I have owned it. And of course, the VT100 on that carpet next to the RA82. If it wasn't for the laptop in the picture, you'd might think that photo was taken in the 80s. But I digress.....

I thought the sector transducer was dirty, because on most drives I have worked on, that's how speed is checked. On floppy drives, it's optical. On RL drives, it's magnetic. At any rate, the led or sensor may be dirty and that could be the problem. Only once did I ever have a detector die, and never the LED, and it was on a floppy drive. I say, first use an alcohol soaked q-tip to clean the led and sensor. It looks like it would be hard to reach without removing the HDA. Hopefully you can reach it without that. Also, unplug and replug the sensor's connector a few times. If you have a scope handy, the transducer wiring comes up to the easily accessible circuit board on top of the HDA. I would look for the pulses on the detector output.

As for the brake, you should be able to see the brake disk pad move up or down when the drive controls engage or release the brake. I think you know that the brake is on top of the motor. I thought, from the video, that the brake was indeed released because of how fast the motor was spinning up, and then came to a halt compared to my (Tim's) RA80. I assume you already had a look at the belt tension and that it looks OK.

Lou
 
Belt tension seems fine as does the tension spring.
I do have a scope though so I can poke at the leads for the transducer however the only way to access the transducer is to remove the HDA but from the manual, all you got to do to release the HDA is lock the heads, release the belt tension spring, remove some bolts, and unplug a harness.

Edit: It was incredibly easy to remove the HDA. Anyways, from a visual point the transducer looks okay but I can poke at it with the scope. Unfortunately the actual pinout differs from the diagram and it does not state the color coding of the wires so all I can immediately find is the +5v.
What should I be looking for on the scope?
RA82trans.jpg

100_1630.jpg

100_1632.jpg
 
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Connect ground on your probe to ground on the drive and scope the tach pulse. Maybe put the scope on 2V/div. It should be good and strong since the phototransistor then drives a Darlington pair. You should see a nice pulse train of increasing frequency as the disk spins up.

While you have things open this far, don't remove the transducer, but still try to wipe the led and receiver with a cloth with some alcohol.

Pontus, if you needed the space so bad, you should have kept the RA82s, and given away your sofa.

Lou
 
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Pontus, if you needed the space so bad, you should have kept the RA82s, and given away your sofa.
Click to expand...

I took the more drastic approach and sold the TV to make space. ;)

don't remove the transducer...
Click to expand...
Too late. I'm assuming it's positioning was vital. Oh well, I had to format the drive anyways.
 
Lou,
An even better smell is from an old TTY. Nothing like that oil smell. And of course the sound. I wish I had kept my TTY
that I had many years ago. Oh well.
Tim Radde
 
Well, at least try to put the transducer back as close to where it was as possible. Hopefully it isn't really used as a sector transducer. If not, you'll be OK.

Selling the TV was no loss. With all this hardware to fix, who has time to watch TV? Ours actually gets more use as a computer monitor than anything else.

Tim, I would guess that the smell from the TTY must have been all that grease / lubricant to keep the mechanical works from seizing up?

Lou
 
My assumption is that with the transducer, I should be seeing a toggle from 0v to 5v whenever I get a pulse however none of the lines are doing this. Either the lines have power (+5 or less) or they don't and none toggle when the drive is spinning up. So either it's stuck on or stuck off.
As a test, I found out the drive shows the same symptoms when the thermostat/transducer harness is unplugged so it is indeed not behaving like it should.
I'm seeing nothing in the manual about the transducer being there for alignment (it just states it's for speed), nor does it show the classic green, red, or blue glue spot to make sure that it does not move around.
How common are replacements?
 
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Lou,
Yes, but it's a very distinctive smell. Even now if I smelled it I'd think back to the good old days.
 
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