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

From: jpero_at_sympatico.ca <(jpero_at_sympatico.ca)>
Date: Sun Jul 21 23:15:01 2002

>
> > 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.
>
> I checked the voltage again, with the servo plug disconnected, and got
> just under 12VDC across the terminals. With the servo plug connected, it
> reads right at 0.4VDC.
>

That means poor power drive to kick in that servo. Voltage should go
up to ~12V or then settle down to holding voltages like 6V or so
depending on that design.

In all TV sets that uses power relay to turn on set using standby
power it's always either 12V or 24V across coil when on. On one set,
I had diode go leaky across that coil. That one I could push down on
that relay and it will stay shut and tv come up. (too weak for
initial pull in.)

Cheers,

Wizard
Received on Sun Jul 21 2002 - 23:15:01 BST