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"Samuel M. Goldwasser" wrote in message
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"N_Cook" writes:

Samuel M. Goldwasser wrote in message
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"N_Cook" writes:





Hey, Geoff.

Actually there's been so few replaced by me in recent years, I don't
think
I've used a generic 240 yet. I've gotten "original Sony" pickups
from
a
reliable supplier, but none lately, so those "NOS" pickups may be
gone.
I do believe that a lot of the "flaky KSS240" problems we
experienced
over
the years were actually bad flat wires. Had one a couple months
back.
Of course I can see where a generic might be shipped unadjusted and
that
could be disastrous. The are three adjustments on the 240 as you
know,
not
just the laser power adjustment. Kind of hard to adjust them while
they
are
playing!

Mark Z.



This generic Sanyo one , oriental script only, had the pot "set" at
zero
ohms as well as zero ohms across the laser


That seems very odd. I don't think I've ever seen that. So, when you'd
removed the solder blob short, did it still not work ? Or was the pot
being
"set at zero ohms" equivalent to it running flat out ? Again, and odd
situation ... Did you reset it to some other value ? How ? Laser power
meter ?

Arfa


Pedants and purist look away now








I set the pot to the value of the original one and worked without
hickup.
Then used the following , adjusting pot, which turned out to be centred
as
far as I could tell by this method, to optimal as first set.

For checking error correction /immunity to errors.
An out of favour audio CD but otherwise in perfect playable condition.
With an assortment of potentiometer back nuts and washers ,small motor
pulleys find a combination that will "fill up" the hole in the centre of
the
CD leaving
just a small hole at the very centre> With a set of "geometry"
dividers
put one point
in this hole and lightly scratch a gouge about halfway along a radius of
the
CD and about 1/4 of the circumference at that radius. Remove the
washers
etc and play on a known good player.
Repeat the groove cutting deeper/wider/number of nearby grooves until
one
track
or part of that track fails to play.
Make a note of the track number and start seconds and finish seconds
into the track/sections of track/s that are absent.
For your own machine every now and then (months) play and note the
numbers
to note
long term drift. More absences/ longer absences over time indicates
deterioration in optics /correction . Use the same CD for checking in CD
repair of other machines and crude adjusting of optical power etc.



That's quite novel. I actually have a test CD from Panasonic, that has
similar linear defects literally 'burnt' into the play layer. There is
also
another one I have, which has a piece of PCB masking tape (the old black
lines used when making your own pcbs) right across a radius. This allows
you
to look at the recovery times of the servos at various rotational speeds.

I'm still a bit puzzled though as to why this 'new out of the box' laser,
came from the manufacturer in an apparently unadjusted condition. I don't
think that I have ever seen this. Most are factory set and sealed. There
are
a few notable exceptions, such as some Pioneer lasers where setting the
output level is an integral part of the service and set-up procedure, but
even then, they are set 'ball park' and seldom require much adjustment to
achieve the 'standard' 1v p-p eye pattern

Arfa


On most occassions I've had a salvaged one , so I automatically change the
pot to whatever the setting was for the current repair as an initial set. So
naturally noticed this new one was at the end of track, 0 ohm. Plugged in
forgetting about the shorting links as I'm not accustomed to seeing them. No
magic smoke, just absolutely no dull red glow in a dark room.