Looking for RL02 cable and terminator

Tony Duell ard at p850ug1.demon.co.uk
Mon Oct 17 18:30:17 CDT 2005

> I did find the tech manuals (from classiccmp's mirror of bitsavers). 
> Tony, IIRC it says the early drives *did not* have brushes and later 
> model ones were equipped with them? Incidentally this drive started life 

That's the opposite to what I've seen and heard. The RL01's in my MINC 
are the earliest version, the drive logic board does not have the RL01/RL02
jumper, it's strictly RL01 only. That drive has the brushes. I've mever seen
an RL02 with brushes.

> as an RL01 but also has a DEC sticker "changed to RL02 by PCO" just to 
> further confuse things.

On a late-design RL01, that's a fairly easy change to make (a few links 
on the boards, new heards, and maybe a new spindle if the older, less 
accurate, one is fitted). 

> Do you still recommend I not install them? I think that airflow and 

I would not fit the brushes.

> centrifugal force might be the only safe way to remove particles rather 
> than "grinding" them across the disk platter surface with a brush, no 
>matter how lightly... 
> I think there may also be a "Fault" if the brushes are not parked?

I don't know if there was a logic change (maybe a different state machine 
ROM or something), but I do know you can get a working RL02 without the 
brush mechanism. I would assume your drive will work without it, at least 
until you prove otherwise ;-)

> Ethan, thanks for the suggestion about using a 40 pin 
> double-ended-Berg cable from inside the drive. I haven't taken the 
> electronics cover off yet. I only have one 8/A and one RL02 so once 
> mounted in the rack cabinet they'll stay there, connected to each 
> other. The 40-pin cable will be, of course, trivial to make IF the 
> pinouts are the same on both ends. 

The pinouts are the same at each end...

But remmber if you do this you'll need to do something about termination. 
Either kluge a resistor network into another connector at the drive end 
of the cable, or use one of the connectors on the back of the drive with 
a real DEC terminator (if you can get one). 

When you open up the drive you'll see a short 40 way ribbon cable with 3 
Berg connectors on it. One plugs into the drive logic PCB, on the bottom 
of the cover. The other 2 plug into the back of the rear panel cable 
connectors.  You could make a longer cable with 2 conenctors near one end 
(drive logic PCB and one of the rear conenctors) and a single connector 
at the other end for the controller. Then just plug a terminator into the 
rear connector of the drive.

One other minor caveat. The drive supplies 5V power on one of the corner 
pins (check the printest) of the connector to power the terminator. This 
is deliberately not connected between the drives (connecting PSUs in 
parallel is generally a bad idea). I don't think it's connected anywhere 
on the contoller board, but you might want to check the printset and 
remove the offiending pin from the controller-end Berg connector if 
necessary when making the cable.


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