"Tim Schwartz" wrote in message
...
Hello,

Sony had a problem with the KSS-240A optical pick ups having an
oscillation problem, usually 800 Hz, and it can be so loud that it
causes the unit to start skipping. Sony had a cure of adding a brass
weight to the optical pick up, and a felt washer to the clamper. I'm not
sure it this applies to all application of the KSS-240A or not.

From a Sony Technical News bulletin that I've got a faxed copy of, the
weight is part number 4-962-979-01, and the screw to attach it is
7-685-134-19. The screw replaces the one holding the PC board with the
pots to the laser. The felt washer is 4-986-769-01, and goes on the
surface of the clamper that touches the disc.

The machines that show this do not do it on all discs, and it seems to
be the worse 5-12 minutes into the disc. Please be aware that original
Sony KSS-240A lasers have 3 pots on the PC board, a cable connector with
a clamp, and that the chip on the bottom is 14 (or is it 16) pins.
There are many 'after market' lasers sold as KSS-240A that have a single
pot, no clamp on the cable connector and an 8 pin chip.

Regards,
Tim Schwartz
Bristol Electronics


wrote:

Hi,

never come across this so thought i'd post and see what people think.

I just got hold of a Sony MHC1600 cd/radio unit. When in cd mode there
is a noise coming from within the unit. I took then unit apart and the
noise is the cd lens assembly vibrating. If you put your finger on the
lens and press (this has probably knackered it anyway) then you can
stop the vibration and noise.

Is the optical assembly the culprit or could it be something else . I
can get hold of another optical assembly easily enough which i'll do
anyway but anyone seen this before?

Kind Regards

Steve

I forgot about that one! The vibration from the spindle motor sets up a
resonance in the pickup. You can see it in the focus error and tracking
error waveforms. Lowering the tracking or focus gain a bit can help also,
and adding some silicon sealer or RTV where the spindle motor contacts the
BD board.

Mark Z.