Hello,
I will try to give you some guidelines to isolate the problem, and how disk detection works ....
1.- When you close the tray with a disc inside, the swich sends a signal to the microprocessor as the tray has been closed, and it returns to the terminal 7 of the KSS240 optics a high value that is applied on the terminal 22 of the integrated M52104 which is part of the optics itself, this means that through the terminal 24 of the same integrated LO signal (laser on), this seems to do well for what you tell, because the laser is visible to the naked eye.
2.- Simultaneously, the lens will try to correctly focus the disk, going down first and then going up to get the FOK signal (focus ok) in terminal 39 of IC109.
This signal will oscillate between '-0.7 and +1.5 V, and only when the FOK signal is present will the disc spin begin.
I understand that the pick-up is the original, or if it has been replaced with a new one, the laser bridge has been removed before installing it.
3.- The power of the laser can be measured by simple law of ohm by measuring the voltage drop in the resistance in series with the terminal 23 and the transistor of the laser diode of the pick-up.
Following these steps you can determine if the problem is laser or not. The laser current is indicated on the laser label itself in mA
I put an image of the KSS-240 electronic
Good luck
I will try to give you some guidelines to isolate the problem, and how disk detection works ....
1.- When you close the tray with a disc inside, the swich sends a signal to the microprocessor as the tray has been closed, and it returns to the terminal 7 of the KSS240 optics a high value that is applied on the terminal 22 of the integrated M52104 which is part of the optics itself, this means that through the terminal 24 of the same integrated LO signal (laser on), this seems to do well for what you tell, because the laser is visible to the naked eye.
2.- Simultaneously, the lens will try to correctly focus the disk, going down first and then going up to get the FOK signal (focus ok) in terminal 39 of IC109.
This signal will oscillate between '-0.7 and +1.5 V, and only when the FOK signal is present will the disc spin begin.
I understand that the pick-up is the original, or if it has been replaced with a new one, the laser bridge has been removed before installing it.
3.- The power of the laser can be measured by simple law of ohm by measuring the voltage drop in the resistance in series with the terminal 23 and the transistor of the laser diode of the pick-up.
Following these steps you can determine if the problem is laser or not. The laser current is indicated on the laser label itself in mA
I put an image of the KSS-240 electronic
Good luck
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Hi Trident,
You can only measure laser output with a laser power meter. Any shop that was authorized to work on Denon and other brands must have one as part of the warranty agreement (in Canada anyway).
The laser current should be written on the head. It is by measuring the laser current as you described and noting the percentage greater than the value marked on the head. You are allowed 10% before declaring the head serviceable. If you buy a cheap head, check to see if the RF output is on spec, measure the current and write down on the chassis Iop= xx.x, the current you measured.
-Chris
You can only measure laser output with a laser power meter. Any shop that was authorized to work on Denon and other brands must have one as part of the warranty agreement (in Canada anyway).
The laser current should be written on the head. It is by measuring the laser current as you described and noting the percentage greater than the value marked on the head. You are allowed 10% before declaring the head serviceable. If you buy a cheap head, check to see if the RF output is on spec, measure the current and write down on the chassis Iop= xx.x, the current you measured.
-Chris
Hi Mooly,
I would like to add that the focus and tracking gain normally do not need to be adjusted. It is dependent on the disc you are playing and an average CD should be okay to adjust the way you are suggesting. CA1094 was replaced at least twice depending on stock. The frequency you apply to the jig is changed to suit that CD. The only truly accurate way to set these gains is to use the adjustment jig described or supplied by the distributor or manufacturer. That and the exact disc they call out. Having said that, there is no exact gain as it depends on the disc. The manufacturer's procedure is designed to put you in the middle of the pack so that most CDs will play without trouble.
It is always better to do things by the book. Once you are very experienced, you can deviate from that procedure to address specific issues. Everything is a trade-off and you have to know the interaction before you start twisting controls.
Hi Nick,
I suspect your disc table (or spindle table) is likely too low. Now that is one adjustment that is very critical. I have brass jigs for setting Denon table heights (and other brands). You can measure the existing height with a caliper - very carefully. Write this down and adjust the height a little bit at a time upwards. I would suggest that for a real head. The fact is, your laser head is a complete unknown and may require a different table height. I would use a jig before doing anything, but you don't have one. Personally, as soon as I found out that the replacement head was different dimensionallky, I would have returned it, or pitched it out. Without the sleeve bearings, I don't expect that head will last very long in playing hours as it doesn't take much wear to make the head jam on the rail.
-Chris
I would like to add that the focus and tracking gain normally do not need to be adjusted. It is dependent on the disc you are playing and an average CD should be okay to adjust the way you are suggesting. CA1094 was replaced at least twice depending on stock. The frequency you apply to the jig is changed to suit that CD. The only truly accurate way to set these gains is to use the adjustment jig described or supplied by the distributor or manufacturer. That and the exact disc they call out. Having said that, there is no exact gain as it depends on the disc. The manufacturer's procedure is designed to put you in the middle of the pack so that most CDs will play without trouble.
It is always better to do things by the book. Once you are very experienced, you can deviate from that procedure to address specific issues. Everything is a trade-off and you have to know the interaction before you start twisting controls.
Hi Nick,
I suspect your disc table (or spindle table) is likely too low. Now that is one adjustment that is very critical. I have brass jigs for setting Denon table heights (and other brands). You can measure the existing height with a caliper - very carefully. Write this down and adjust the height a little bit at a time upwards. I would suggest that for a real head. The fact is, your laser head is a complete unknown and may require a different table height. I would use a jig before doing anything, but you don't have one. Personally, as soon as I found out that the replacement head was different dimensionallky, I would have returned it, or pitched it out. Without the sleeve bearings, I don't expect that head will last very long in playing hours as it doesn't take much wear to make the head jam on the rail.
-Chris
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