17 May
2010
17 May
'10
2:13 p.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Tony Duell
Sent: 17 May 2010 20:18
To: cctalk at classiccmp.org
Subject: Re: RD53 Restoration
Indeed, if only I knew what it was!
Yes "blipping" the coil with a 9V battery moves the heads. When the
drive
was powered on I also measured the voltage by
attaching a probe to
each end
of the coil cable, in that case I measured about
1.3V only. So I am
guessing
the coil is OK. Next step is to swap the boards
back again.
And then fix the real fault :-)
More seriously, it sounds like the positioner coil is not being driven
hard enoguh to move the heads
Well that is what I was thinking, but if the replacement boards I used were
known to work then I would have hoped for better results. I suppose they may
have been damaged during removal or when I fitted them to my unit.
-- and if the coil was open-circuit I
would
ecpect the servo sysem to try to drive it very hard to attempt to get
some movement. Normally there are various conditions which have to be
satified (motor up to speed, no write current unless write gate is
asserted, only one head selected, etc) before the heads will move. It's
entirely possible the problem is in one of those areas.
The problem for me is how to diagnose this. I am pretty sure the motor is up
to speed. However one thing that does seem slightly odd is that it starts to
spin the disk down quite soon after power up. Previously with the old
boards, when it worked, it would move the heads quite some time after power
up, I am pretty sure this is long after the new boards give up and start
spinning down again.
Is it possible that the fact that for a time the heads were stuck, because
of the sticky goo problem RD53s suffer from, could have caused a follow-on
problem?
-tony