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Sony CDP790 and KSS240 Restoration Project
Sony CDP790 and KSS240 Restoration Project
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Old 3rd January 2021, 04:51 PM   #221
maouna is offline maouna  Greece
diyAudio Member
Join Date: Oct 2008
The laser unit i received from ebay didnt work.It was rusty and oxidized.thankfully i got a refund.I was pointing the phones camera on the laser and no light would come out.So i unsoldered the small ribbon that goes to the PD,LD and tested both of the diodes with the diode tester.they seemed ok but no light coming out of the laser (iam looking with my phones camera)so i made a small current source around 35ma as the one on the schematic of kss240 and tested again.no light out of the laser diode.I was wondering whether it is easy to replace the diode itself and get it working as there are quite cheep at alliexpress.the old diode came out pretty easily as it was glued.
I found some potential replacements.

RLD78MRA1 pdf, RLD78MRA1 description, RLD78MRA1 datasheets, RLD78MRA1 view ::: ALLDATASHEET :::
QL78D6S-A datasheet
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Last edited by maouna; 3rd January 2021 at 04:55 PM.
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Old 3rd January 2021, 05:23 PM   #222
Mooly is offline Mooly  United Kingdom
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Join Date: Sep 2007
Sony CDP790 and KSS240 Restoration Project
A diode tester probably wouldn't be any use on a laser diode because the current needed for lasing to start is probably much higher than the test current. There is also the real risk of damaging the LD due to transient spikes which happens in nano seconds and can damage the facets of the diode chip.

The diodes do come out of most pickups very easily but whether a replacement will work without the internal optics being aligned to it is another matter.

There is a thread here which is long and spans a few years:
Dead Laser Pickups - why not replacing the Diode only?
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