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Default DVD Drive motor power

"DA" wrote in message
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DA wrote:
Chas wrote:

Working on a friends Goldstar GBV441 DVD/RW/CD/RW-VHS/RW unit.
The DVD motor does not spin.
. . I did cut one wire on the DVD drive showed resistance.
to be sure
(cheapo multimeter) I ran 5 vdc (from a model RY controller) and the
spun with no problems...

DVD spindle motors are usually brushless DC (BLDC) motors that would not
work by just powering them with DC - you'd need a driver IC that creates
the proper waveforms. So, my guess is that this deck has just a simple DC
motor instead? Otherwise the 5VDC trick wouldn't work. How many wires are
coming out of that motor?

Actually, most bog-standard DVD decks found in domestic players, *do* employ
a Mitsumi DC motor of exactly the same variety as found on CD decks. They
frequently fail, but not totally. They are usually just reluctant to start
up, and if you give them a bit of help, they will spin up the disc and
operate normally until next time. Occasionally, the symptom is of slow
rotation. The fact that the motor appears not to be being driven, may be a
secondary symptom of the real fault. It depends on what startup sequence
this particular player uses. Some will run the disc up right away, and then
go looking for output from the optical block. Some will attempt to obtain
focus first, and if they can't, will rotate the disc in small pulses, to see
if they can find an area where they can obtain focus, just in case the first
area tried was dirty, or badly damaged. But some will only try to obtain
focus in one place. If that doesn't happen, perhaps because the laser is
defective, the coarse spindle drive and servo will never be enabled, and
power will never be applied to the motor.

The motor will be driven by (often) a small SIP IC, but sometimes by a
somewhat larger IC, that looks after the sled motor as well. The switch on
the small board that the motor is primarily connected to, is nothing to do
with control of the motor. It is the laser 'home' switch. The board is just
a convenient 'via here' point to anchor the motor's wires to. Rarely, the
drive IC is actually on this little board, but mostly, it will be found down
on the board that the little switch board connects to. Normally, you will
find either a cable with half a dozen wires in it, going between the switch
board and the main board, or sometimes, a flexiprint (not to be confused
with the flexi from the laser). This cable also carries drive for the sled
motor. If you look close to where that cable arrives at the main board, you
will probably find the drive IC (s). You can check that there is some
voltage present on the supply pins of the chip. Typically, this will be
around 8 volts. If there is voltage present, but nothing is output to the
motor, then you will probably not progress much further without schematics,
and a degree of experience in troubleshooting the servo / drive circuitry.
As a slight aside, if you deliberately move the sled some distance up the
slides, then apply power, and the sled motor runs to return it 'home', as I
believe you stated was the case, then the supply for the spindle motor
driver is almost certainly present, as sled and spindle drives usually share
a common supply. As another quick test, does it play a CD still ?