Denon DCD-520,Opamps replacement,increase laser power to read CD-RWs

[maouna]

Hello.I have this old vintage cd player Denon dcd-520. I fully recapped it and removed the 2 muting transistors it had and now theres only a small audible pop during power on and off but its ok.Original Laser is KSS-150A.It reads well all original cds and all cdrs but not CD -RWs. I had a cheap KSS-210A bought of ebay and gave it a try.it worked out of the box.I dont have an oscilloscope.

I raised the laser power by turning the trimmer a bit and now it reads CD-RWs.

Does anyone have a service manual for my model?
How to know if the increase of the current is within specs of the laser so as not to destroy it or destroy any other part on the main board?
The opamps it uses for audio are 4 pieces NE4558.I installed IC sockets there.I also have NE5532,TL072 (4 pieces each) and 2 pieces OPA2134.What do you suggest to use?

 

[JonSnell Electronic]

Raising the laser power is a sure way of destroying it. Purchase a good stock of KSS210s if you want to do that.
Try setting up the focus gain first!

 

[JonSnell Electronic]

The opamps it uses for audio are 4 pieces NE4558.I installed IC sockets there.I also have NE5532,TL072 (4 pieces each) and 2 pieces OPA2134.What do you suggest to use?

I suggest the original op amps are best to use. Introducing DIL sockets will cause you intermittent problems down the line.

 

[Mooly]

Although I agree fully with Jon over the laser question, I would certainly try some different opamps to the 4558 opamps... and you know what, I'm going to say to try your TL072's and give them a fair hearing.

 

[maouna]

How can i measure the current that the laser draws when i change it through the trimmer?

 

[Mooly]

Look at the circuit diagram. There will be a low value resistor in the laser drive circuitry from where you can calculate the current from the voltage dropped across this resistor.

The resistor is typically located on the small transistor that directly supplies the laser diode.

 

[maouna]

I cant find the service manual of my model but i found something similar.I measured the voltage across these parallel resistors and the current was 56mA.(This current is the increased current by turning the trimer at about 45 degrees from its factory position).
With the trimmer at is factory position the current was 45.2mA

But what is the factory operating current of this chinese KSS210A?
Can i rely on this datasheet for thresshold current and operating current?

 

[Mooly]

Those are the resistors, it is similar in all players.

The genuine Sony pickups had the preset laser current marked into the serial numbers last three digits, however the copies don't seem to follow that pattern.

This would have been 47.8 milliamps. I'd suggest you set it using a good Red Book commercial CD of good reflectivity and set the RF for around 1.5 volts peak to peak on the scope.