On Wed, 07 Nov 2012 07:58:06 -0600, in sci.electronics.repair you wrote:

SNIP

I read your original post, and I too did not deduct from it that you
were a consumer electronics wiz. If you had been, I thought you would
have mentioned that you had checked any switches involved in the tray
operation. I think you might be better off taking a deep breath and
saying you had checked such items, rather than criticizing someone who
was trying to help you.

Hi Ken,

I am sorry I did not mention that I looked for such a switch in my
original post.

If there is a "switch", it is in a hidden location since I did not
disassemble the tray from the rest. Note: I opened the tray all the
way, then pulled the plug in my search for a switch.

If I had a SM, I would know what method is used to determine the tray
status.
John

Hi, i'll try to write in english..

some times i've heard about this problem, i know on cdrom readers there is
a lever type switch with the lever pushed in one side when tray opens and the
other when it closes, if when the user commands to open, the tray reaches
the end of the run the board (i think) senses motor's too much current use and
revert the direction, i think the switch is a single contact but in some way
when the tray closes there is no invertion or maybe the switch has 3 contacts
but 2 are common so the "close" contact works, the "open" not..
this sw. is on one side of the tray, if you watch under the bottom side is made
like __/'''''''''''''''''''''''''''\___ this... it is on the front, i think.
i've been clear?

Bye..

wrote in message
...
On Wed, 07 Nov 2012 07:58:06 -0600, in sci.electronics.repair you wrote:

SNIP

I read your original post, and I too did not deduct from it that you
were a consumer electronics wiz. If you had been, I thought you would
have mentioned that you had checked any switches involved in the tray
operation. I think you might be better off taking a deep breath and
saying you had checked such items, rather than criticizing someone who
was trying to help you.

Hi Ken,

I am sorry I did not mention that I looked for such a switch in my
original post.

If there is a "switch", it is in a hidden location since I did not
disassemble the tray from the rest. Note: I opened the tray all the
way, then pulled the plug in my search for a switch.

If I had a SM, I would know what method is used to determine the tray
status.
John


The reason that this problem happens, is that although we all know that
pushing on the tray to close it is a bad idea, manufacturers know that
punters are gonna do it. So they arrange for the micro to look at the 'tray
open' switch from two points of view. First, they check if the switch
contacts close whilst the tray motor is running. When that is true, the tray
is open, and the power to the motor is cut. The switch is then monitored for
it going open when the motor is not running. When that is true, the motor is
run in reverse to close the tray. This allows the tray to be pushed to the
point of the switch re-opening, before the motor takes over and finishes the
job. This sequence can of course be over-ridden by the open / close button
being pressed. This takes priority over the 'motor stopped - tray switch
closed' condition that prevailed at the end of the opening sequence.

The problems start when the contacts on the 'tray open' switch get sooty, as
they frequently do. So the tray opens, the switch closes, the motor stops,
and then the switch momentarily opens again, even though it is firmly
mechanically pressed, due to the sooty contacts not making very well. This
is immediately seen as the tray having been pushed by the owner, so the
system control micro starts to run the motor in reverse. This all happens so
quickly that what you get is effectively the tray fully opening, and
immediately 'bouncing' back closed.

Although over the years I have come across the odd exception to the
mechanical switch scheme, it is by far and away the most commonly used tray
management system from all manufacturers, Usually, the switch is an easily
visible leaf contact type, mounted somewhere near the front of the deck, but
on some mechs, it can be located in much harder to see places. Also, some
mechs use miniature plunger switches in all sorts of obscure locations, and
still others use either of those switch types, but mounted to the side of -
or even under - a mechanical 'cam' that's part of the tray open / close -
disc clamping arrangement.

Arfa