Dead Laser Pickups - why not replacing the Diode only?

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Hi John,
Yes, it will need a setup. It will also need an experienced hand to see if it is a junk head or not.

If you don't have a good audio technician align it for you, you would be ripping yourself off for performance and sound quality. A head out of alignment / adjustment will have a lot more errors which will cause digital errors and therefore, poor sound quality compared to what it would normally be capable of.

So, you need an oscilloscope capable of 0.5uS per division. NOT A DIGITAL SCOPE! You need a good DVM and the right filters and an oscillator. On top of this, you need the correct lubricants and test CDs. That's a bare minimum. You probably also need a new disc motor too.

Find a good tech in your area and use him. I have everything I listed and more for servicing CD players in case there are no other options for you. I'm in Canada though.

When removing the head, it is very easy to damage the fingers to the position resistor. This one may or may not use one, I'm not sure without looking it up. Anyway, I do not recommend that you attempt to service it yourself. Also, the rubber dampers will be rock hard by now. There are no replacements that I know of. The only fix is to simply remove them, but do not lose the spacers or mix them up!

-Chris
 
Unfortunately I am still not able to find those company, which are able to remove the old diode replace the new diode include all necessary mechanical adjustments.
Who can help to find such companies or guys?
I also had a question about replacing the diode in the KSS-190A and KSS-271A. I will buy diodes, I will take 5 pcs. and I’ll try to do it myself. But most likely, in addition to adjusting the diffraction grating, the position of the photodiode array can be rearranged, and this greatly complicates the situation.
Since the diffraction adjustment is not possible in these blocks, it is glued, the diode itself needs to be adjusted.
 

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The diode in KSS-190A has so far returned to its place, it is still working, but the radiation power is very weak, it will not detect the CD-R at this radiation power. In feedback, the RF amplifier CXA1081A (between pins 2-3) increased the resistance of the resistor to 47k. To artificially raise the level of the RF signal, CD-Rs are now detected, but this is a temporary measure to use it at least somehow ...
 
Any photos of the glued grating? I remember on the
french site “vintageaudiolaser” the owner swapped
the diode of a BU-1 and got good results by carefully
moving and probably tilting the diode.
But in the BU-1 there is room for this, it allows a little play
for the diode. Look carefully at the photos

A l’atelier... (page 54) - vintage-audio-laser.com

scroll down to the bottom.
 
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Maybe. But I was playing around with a BU-1 that did not need repair.
After removing the original diode and after putting it back, the Eyepattern was still there, though very blurry. Only after I touched/moved the grating (which was secured by thread locking fluid) things did not work any more.
So I assume, if there is some room for the diode to move, there is a chance
to do an alignment by positioning the diode.
Does the KSS-190 give some room for the diode to me moved?
Ist there also a spring that fixes parts like the diode?
In the BU-1, the spring gives pressure on the grating as well as on the diode, so things cannot move out of alignment...
All the best,
Salar
 
How do you know the diode is weak or broken to begin with? There could be problems with other parts of the circuitry that controls current etc. to the diode.

Surface mount capacitors, especially old ones, could degrade, as well as tantalum. I have swapped laser assemblies as a first step to repair, but it made no difference, and the problem was in the circuitry. Replacing the diode itself, which requires all the meticulous alignment etc., may best be a last resort.
 
This topic is about changing the diode (as a last resort) and not intended to discuss other possible repairs…
BTW I have a laser power meter and it looks like the "original" diodes available are all crap. From 40 I measured, only 8 barely reached the output power of the already worn original. So modifying APC and fitting in
modern diodes will be the next obstacle...
 
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This topic is about changing the diode (as a last resort) and not intended to discuss other possible repairs…
BTW I have a laser power meter and it looks like the "original" diodes available are all crap. From 40 I measured, only 8 barely reached the output power of the already worn original. So modifying APC and fitting in
modern diodes will be the next obstacle...

Okay, but I could not tell there was a "last resort" aspect to this in the first post, or most of if not all other posts.

Why would original, presumably unused diodes be so low in output? Don't they degrade with use?
 
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