This DVD player has a strange fault. There is a motor which, via a
belt, closes the drawer and, upon doing so, then raises the laser
block. However, this motor does not switch off upon completion of the
sequence, and nor does it reverse direction if eject is pressed - so
you have to manually remove the disc.

There are no sensors at all on this part of the mech, no leaf
switches to indicate the drawer is closed. Not only that, but the
motor is fed directly from the power supply pcb.

Any thoughts before I dig further into that pcb?
TIA
-B

"b" wrote in message
...
This DVD player has a strange fault. There is a motor which, via a
belt, closes the drawer and, upon doing so, then raises the laser
block. However, this motor does not switch off upon completion of the
sequence, and nor does it reverse direction if eject is pressed - so
you have to manually remove the disc.

There are no sensors at all on this part of the mech, no leaf
switches to indicate the drawer is closed. Not only that, but the
motor is fed directly from the power supply pcb.

Any thoughts before I dig further into that pcb?
TIA
-B

I'm sure that you must be missing something here. I don't think that I have
ever seen a loading motor driven directly from a power supply. If that were
the case, how would the system control IC look after running it, stopping
it, and determining which direction it has to run (open / close) ? They are
invariably driven via a custom motor driver IC. Sometimes, this is a
through-hole SIL device with a heatsink tab - looks a bit like a car radio
audio IC - and sometimes, it is a DIL or s.m. job. Very occasionally, they
are driven by low level logic feeding a four-transistor bridge.

As to there being a switch, there almost always is, although it may be
hidden deep in the mech somewhere. Look for a couple of wires from the main
deck loom, which seem to disappear somewhere that you can't see the ends of
them. The alternative, that I have seen used a couple of times over the
years, is to sense the motor stall current when the unload or load operation
completes.

And on that tack, are you *absolutely sure* that the loading cycle *totally*
completes ? If the motor is still running at the (perceived) end of the
cycle, and it's driving a belt, then that would imply that at this time,
that belt is slipping on the motor's pulley. This is a common scenario that
I see probably once a month in various players. The loading mech has to do a
lot of work at the end of the cycle, not the least of which is lifting the
weight of the deck, and (and this is key) often moving a latch bar that
secures the tray closed. The sense switch is sometimes at the end of this
bar, so although the loading cycle *appears* to complete in that you see the
deck go up, it actually *doesn't* complete in that the belt slips under the
load of trying to move that bar into place.

I would replace the loading belt with a new one, slightly tighter than
what's on there now to allow for stretch. Clean the pullies with IPA at the
same time. I would say that there is a better than 50% chance that this will
clear the problem.

Arfa

"b" wrote in message
...
This DVD player has a strange fault. There is a motor which, via a
belt, closes the drawer and, upon doing so, then raises the laser
block. However, this motor does not switch off upon completion of the
sequence, and nor does it reverse direction if eject is pressed - so
you have to manually remove the disc.

There are no sensors at all on this part of the mech, no leaf
switches to indicate the drawer is closed. Not only that, but the
motor is fed directly from the power supply pcb.

Any thoughts before I dig further into that pcb?
TIA
-B

I'm sure that you must be missing something here. I don't think that I have
ever seen a loading motor driven directly from a power supply. If that were
the case, how would the system control IC look after running it, stopping
it, and determining which direction it has to run (open / close) ? They are
invariably driven via a custom motor driver IC. Sometimes, this is a
through-hole SIL device with a heatsink tab - looks a bit like a car radio
audio IC - and sometimes, it is a DIL or s.m. job. Very occasionally, they
are driven by low level logic feeding a four-transistor bridge.

As to there being a switch, there almost always is, although it may be
hidden deep in the mech somewhere. Look for a couple of wires from the main
deck loom, which seem to disappear somewhere that you can't see the ends of
them. The alternative, that I have seen used a couple of times over the
years, is to sense the motor stall current when the unload or load operation
completes.

And on that tack, are you *absolutely sure* that the loading cycle *totally*
completes ? If the motor is still running at the (perceived) end of the
cycle, and it's driving a belt, then that would imply that at this time,
that belt is slipping on the motor's pulley. This is a common scenario that
I see probably once a month in various players. The loading mech has to do a
lot of work at the end of the cycle, not the least of which is lifting the
weight of the deck, and (and this is key) often moving a latch bar that
secures the tray closed. The sense switch is sometimes at the end of this
bar, so although the loading cycle *appears* to complete in that you see the
deck go up, it actually *doesn't* complete in that the belt slips under the
load of trying to move that bar into place.

I would replace the loading belt with a new one, slightly tighter than
what's on there now to allow for stretch. Clean the pullies with IPA at the
same time. I would say that there is a better than 50% chance that this will
clear the problem.

Arfa

On 5 nov, 10:20, "Arfa Daily" wrote:

I'm sure that you must be missing something here.

Hi Arfa, and thanks for your thoughts.

It did seem very unusual to me that a motor would be connected to the
psu; as you say , what about the issue of control of the voltage? That
said, the psu in this unit is a huge pcb with what appears to be
several circuits so I didn't suspect it too much. The load cycle was
OK and the laser came on/disc played after its completion, with just
the constantly running/straining motor as an indication all was not
well.

Well, I just took another look at it in the cold light of day and the
answer was staring me in the face. The Phanton Twiddler had obviously
been at this player before it reached me. There was a motor connector
on the logic /processor pcb but someone had connected the motor to a
vacant identical one on the psu which was supplying a fixed 5v line.
changed 'em over and all OK....

can't believe I was so stupid not to have noticed that - I blame these
nocturnal fixing sessions!

cheers,
B.

"b" wrote in message
...
On 5 nov, 10:20, "Arfa Daily" wrote:

I'm sure that you must be missing something here.

Hi Arfa, and thanks for your thoughts.

It did seem very unusual to me that a motor would be connected to the
psu; as you say , what about the issue of control of the voltage? That
said, the psu in this unit is a huge pcb with what appears to be
several circuits so I didn't suspect it too much. The load cycle was
OK and the laser came on/disc played after its completion, with just
the constantly running/straining motor as an indication all was not
well.

Well, I just took another look at it in the cold light of day and the
answer was staring me in the face. The Phanton Twiddler had obviously
been at this player before it reached me. There was a motor connector
on the logic /processor pcb but someone had connected the motor to a
vacant identical one on the psu which was supplying a fixed 5v line.
changed 'em over and all OK....

can't believe I was so stupid not to have noticed that - I blame these
nocturnal fixing sessions!

cheers,
B.



Glad it turned out to be a simple one - heaven knows, we all need a few of
those from time to time !! And don't beat yourself up too much about not
spotting it right off - I think we've all been there more than a few times
d;~}

Arfa

On Thu, 5 Nov 2009 04:39:13 -0800 (PST), b
wrote:

On 5 nov, 10:20, "Arfa Daily" wrote:

I'm sure that you must be missing something here.

Hi Arfa, and thanks for your thoughts.

It did seem very unusual to me that a motor would be connected to the
psu; as you say , what about the issue of control of the voltage? That
said, the psu in this unit is a huge pcb with what appears to be
several circuits so I didn't suspect it too much. The load cycle was
OK and the laser came on/disc played after its completion, with just
the constantly running/straining motor as an indication all was not
well.

Well, I just took another look at it in the cold light of day and the
answer was staring me in the face. The Phanton Twiddler had obviously
been at this player before it reached me. There was a motor connector
on the logic /processor pcb but someone had connected the motor to a
vacant identical one on the psu which was supplying a fixed 5v line.
changed 'em over and all OK....

can't believe I was so stupid not to have noticed that - I blame these
nocturnal fixing sessions!

cheers,
B.


Bwa-ha-ha-ha... Amazing what people can do if given half a chance. The
fact that the previous person didn't destroy it is amazing.