Multibus ST-506/QIC-02 (was: Re: SGI IRIS 1400 ...)

From: Tothwolf <tothwolf_at_concentric.net>
Date: Sun Jul 21 19:53:01 2002

On Sun, 21 Jul 2002, Tony Duell wrote:

> You'd be suprised how many people have a DMM only these days. I've even
> been told that analogue multimeters are obsolete and useless (!).
> Needless to say I don't believe that. Yes, digital meters are better for
> making accurate measurements of steady signals, but analogue meters are
> _far_ better for looking at changing signals, or for spotting the peak
> in voltage when adjusting something, or....
>
> What do I use? Both, of course, but normally an analogue one. Accurate
> measuemetns are rarely needed in electronics.

I've got dozens of meters (though only a few sets of good probes...) Most
of them are digital, but I still find myself using an analog fairly often.

> Eh? Do you mean it's at 0V, and goes up to 0.4V after 8s, or what. Your
> message seems to say it changes from 0.4V to 0.4V.

It starts out at 0V, then jumps to 0.4V at ~8 seconds.

> I think that sounds far to low to move the heads -- I would expect a few
> volts at least. So you might well have a servo problem. As a first
> attempt (not having schematics), check the power transistors on the
> servo board. I think 6 of them are to drive the spindle motor, the other
> 4 (?) are the servo power amplifer. The V150 I worked on used discrete
> transistors (not an amplifier chip), so I would guess the V170 does too.

There are a whole mess of transistors mounted to heat sinks on the servo
board. I think I see which 4 are for the servo.

> Maybe some kind of head lock releasing.

I didn't exactly hear the heads load though. Maybe I'm expecting a noise
these drives don't make.

> Now that I can't remember. 3600 rpm???

That seems about right, but this drive sounds different. Maybe it is just
designed in such a way that it sounds different than most drives I'm used
to.

> > I really should build a clean-box...
>
> As should I...

Are there any "complete" plans for one anywhere? The only reason I haven't
built one yet is that I haven't had time to design one...

> No, there is no separate spindle brake. The spindle brake is a relay
> that disconnects the motor windings from the drive electronics and
> connects resistors across them.

Why would the motor still feel fairly stiff then? Are the magnets used for
the spindle motor very strong?

> There's no similar connector on my V150, so I have no idea what it is
> for. Maybe there is a positioner lock that's fitted inside the HDA, and
> this is the connector for it.
>
> What connectors do you have on your servo board? the V150 (new style?)
> one has a small 2 pin connector for the servo input from the other
> board, a larger 2 pin connector near it for the positioner coil (that's
> the one you should have been checking the voltage one), a 10 pin (or so)
> connector for the spindle motor at the back edge, another 2 pin
> connector for the positioner lock solenoid and a 34 pin (or so)
> connector for the control signals from the other board.

That sounds identical to what this one has. Maybe the positioner lock
solenoid is located entirely inside the HDA on the V170.

There was still (factory?) orange epoxy-paint over the 4 screws that held
the pc boards in place before I removed them, so I don't think anyone else
previously removed them.

-Toth
Received on Sun Jul 21 2002 - 19:53:01 BST