"Arfa Daily" wrote in message
...


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

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

First time for years (no salvaged one on hand) I replaced old with
new
but
had forgotten about those antistatic shorting links, wasting time
trying
to
find the short. Nothing on the box about the shorting link, only
graphic
showing use antistatic wrist strap for assembly
Do they all have these solder-across semicircle land pairs?
This one Sanyo SF-P101 has them , so do KSS213 and K SM213, all ?
Is there something in the laser assembly that is especially prone to
static
damage?

Yes, the laser diode. There's generally very little circuitry between
the
cable and laser diode and it can be damaged by any number of things
including
ESD.

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/

But is a CD laser diode any more susceptible to ESD damage than a bulk
standard red LED or a 1N4148 say, in otherwise the same poor handling
circumstances?

YES! A 1 ns current spike with a peak just above the laser diode's
maximum
rating can destroy it. Accidentally connecting a charged 0.01 uF 5 V cap
across a laser diode will destroy it. Etc., etc. Look at it the wrong
way.....

--
sam

All absolutely agreed. However, to answer one of Mr Cook's earlier
questions, given that they do have this extreme static sensitivity,
curiously, the answer is no - not all replacement optical blocks *do* have
the laser diode shorted for transit. As well as shorting blobs on the pcb,
other methods of shorting that may be found are a thin metal plate in the
ZIF connector that some have, and a tiny switch that I have seen fitted to
some DVD optical blocks. And of course the solder blobs on the flexiprint
tail rather than on the board, and the 'snip-off' piece of flexiprint (two
varieties) to be found on some Panasonic lasers.

Arfa


And some models like the KSS-240 have the power limiting circuit built in;
no shorting required.

Mark Z.