11/45 RL02 faults when RX02 is on

[Allison]

>
>Subject: Re: 11/45 RL02 faults when RX02 is on
>> 
>> Ok, is there a known severe RFI problem with mounting a RX02 directly on top 
>> of a RL02 in an H960???

You have to be kidding me.  I have that arrangement and it's solid. The RX02
bottom is well shielded as it the top of the RL02 logic.

>
>I've not heard of one, but then again, I've never actually tried that 
>mounting arrangement. I know DEC stated that certain peripherals should 
>have their own racks, I always figured this was, in part, to sell more 
>cabinets, but I assume there might have been some interference issues as well

Most of that was for cooling and accessability for service.


>> I went back to look at the "RL02 faults when RX02 is on" problem. I had left 
>> the rear top cover of the RL02 up in the service position (with the drive 
>> extended from the rack). I retested without touching anything. Sure enough, 
>> the problem was "gone". The RL02 wouldn't fault no matter what. So I put 
>> that rear top cover back down and screwed in the 4 screws, then pushed the 
>> RL02 back into the rack and voila - the problem reoccured. The RL02 will 
>> fault just after spinup IF the RX02 (which is mounted directly above it) is 
>> powered on. Aha... I was now thinking a cable problem! I figured pushing the 
>> RL02 in and out of the rack seemed to be the causative factor, bending a 
>> cable just right or something.
>
>The spindle motor in each drive of the RC02 is a fairly crude induction 
>motor. I could well believe it has enough stray field to cause 
>interferende (It's not that well shielded). Maybe that's being picked up 
>by the RL's head and upsetting the servo.
>
>Here's an idea. Take the fan plenum off the back of the RC02 (4 screws, 
>IIRC, and uplug the fan calbe). Then unplug the 3 pin connector on the 
>back of each drive (115V AC to the spindle motor). Try the system now. 
>Obviously the RC02 can't run (the spindles won't be turning), but if 
>there are no disks in the drives the system can't realise this. Have the 
>RC02 powered up (so its PSU is running, and all the logic is powered) and 
>see if the RL behaves now. If so, it pretty much confirms it's 
>interference from the RC02's spindle motors.
>
>-tony

I've been doing it for years and it works for me.

Allison