Hi,
There is some truth in Jean-Paul’s remarks. There is a small range of current the diode actually “lasers”. Below a threshold it will not laser at all and it is simply a LED and above a certain current level the laser will be destroyed.
Duo,
On most Sony’s there is a test point on the board labelled “RF”. It is near the connector where the cabling from the laser head enters the board. A “GND” point for hooking up the gnd lead of your probe is also nearby. There you will see the “HF eye pattern” as read from the disk. The nominal amplitude is 1 V_pp there for the Sony’s I have seen.
Good luck
There is some truth in Jean-Paul’s remarks. There is a small range of current the diode actually “lasers”. Below a threshold it will not laser at all and it is simply a LED and above a certain current level the laser will be destroyed.
Duo,
On most Sony’s there is a test point on the board labelled “RF”. It is near the connector where the cabling from the laser head enters the board. A “GND” point for hooking up the gnd lead of your probe is also nearby. There you will see the “HF eye pattern” as read from the disk. The nominal amplitude is 1 V_pp there for the Sony’s I have seen.
Good luck
Okay, I'll try adjusting it by that. My scope doesn't have a setup for measuring voltage... Should I be able to use a vacuum tube voltmeter instead because of its super high impedance??? I guess I could feed a known 1vpp sig into the scope and mark where it shows up but that would be a bit of a pain...
Thanks
Thanks
Definitely NOT You must watch the peak to peak value on a scope. It is not a steady sine signal, although it looks somewhat to a sine. If you set the laser too high there is a serious risk of damaging the laser.
If your scope is not calibrated, this is the way to go then. But if the scale is accurate in V/div, reading the divisions on the screen is accurate enough. Oh, and your scope must be of at least 10 MHz BW.
Duo, it takes some experience but putting the player on its side with the cover off is common practice.
Some players have a dummy mode for adjusting the laser current.
Sometimes a jumper, sometimes you have to push a certain code on the panel for this.
Maybe obtaining a service manual will help ? It will tell you too how to adjust tracking and focus ( if applicable ).
Some players have a dummy mode for adjusting the laser current.
Sometimes a jumper, sometimes you have to push a certain code on the panel for this.
Maybe obtaining a service manual will help ? It will tell you too how to adjust tracking and focus ( if applicable ).
I have a Sony CDP-910 (the same chasis is used on the CDP-222ESD and CDP-505ESD as well) that started skipping CDs. I got the service manual and went through the allignment proceedure and got things going again for a while. There was no mention of laser current adjustment, but the adjustment that was radically changed was the Focus Bias, all the way to one limit. After a few months the skipping started again and I put it aside for a long time. I just started playing with it again and initially could not get it to play anything. As an experiment I changed the resistors in the Focus Bias adjustment network to give a larger range of adjustment and I was able to get it palying CDs again. Sometimes it still take a couple of attempts for it to recognize some CDs.
I wonder if the focus bias could be your problem. To adjust the focus bias, hook your scope up to the RF test point and GND. In my case the adjustment pot is the one closest to the test point. Adjust for the best "eye" pattern.
I don't see any mention in my service manual about adjusting the laser diode current. Since this is a late '80s vintage model, I would not doubt that it could use a boost. Any thoughts on where the adjustment might be located?
I would also like to figure out what the root cause of my need for such a high level of Focus Bias is. Is there some link between laser diode output and focus? It doesn't seem likely. I did look at a book at an electronics store that indicated mechanical height adjustment of the disc over the optical pickup can affect the focus bias. This makes sense. Can this height creep over time? How would it be adjusted?
I wonder if the focus bias could be your problem. To adjust the focus bias, hook your scope up to the RF test point and GND. In my case the adjustment pot is the one closest to the test point. Adjust for the best "eye" pattern.
I don't see any mention in my service manual about adjusting the laser diode current. Since this is a late '80s vintage model, I would not doubt that it could use a boost. Any thoughts on where the adjustment might be located?
I would also like to figure out what the root cause of my need for such a high level of Focus Bias is. Is there some link between laser diode output and focus? It doesn't seem likely. I did look at a book at an electronics store that indicated mechanical height adjustment of the disc over the optical pickup can affect the focus bias. This makes sense. Can this height creep over time? How would it be adjusted?
Well, I'll see if I can get a manual then. I know what you mean about frying lasers with the current adjustment, I've fried many cd players with that pot not knowing exactly what it did... I guess I'll look into that focus adjustment too, that makes some sense as well. I heard that blue laser diodes are excellent in cd players, a friend of mine has a sony ES model of some sort with a blue laser diode in as a mod. His sounds very nice. I also have a CDP-CE505 here too but I don't use it simply because of the same problem my 305's been having. I hate unreliable equipment... Either way, I'll look into some more adjustments any how. THis thing isn't all that old so I don't see why I should retire it just yet. Heh, maybe the diode's burning out cause I use the darn thing 24/7 and have been since I got it a year ago.
I remember that when I got it, I could even give the transport fairly excessive shocks without any sort of skipping whatsoever. Now it's quite sensitive.
Either way, I'll look into some more adjustments any how. THis thing isn't all that old so I don't see why I should retire it just yet. Heh, maybe the diode's burning out cause I use the darn thing 24/7 and have been since I got it a year ago.I remember that when I got it, I could even give the transport fairly excessive shocks without any sort of skipping whatsoever. Now it's quite sensitive.
lol, yeah, I fry a lot of things unless I know what I'm doing...
at least I know what that adjustment in a transport is for now...
I used to always think it was some sort of tracking pot...
BTW, this laser current pot is the only pot in the whole cd player, I can't find any focus or anything!
I guess I just have to work with this then...
at least I know what that adjustment in a transport is for now...
I used to always think it was some sort of tracking pot...
BTW, this laser current pot is the only pot in the whole cd player, I can't find any focus or anything!
I guess I just have to work with this then...
Well, kinda slipped cleaning it. I did however find the initial problem...
It seems I got lubricant on the semitransparent mirror inside the pickup assembly when lubricated gears. It as causing the problems especially as it collected dust that may have floated by.
I know I can get another transport for this thing for cheap, I'm just trying to find exactly where...
It seems I got lubricant on the semitransparent mirror inside the pickup assembly when lubricated gears. It as causing the problems especially as it collected dust that may have floated by.
I know I can get another transport for this thing for cheap, I'm just trying to find exactly where...
Hey, that thing was sticky as heck. It really needed some oil.
I've lubed many transports with fine results. I guess somehow I dripped some oil right into the transport.
Either way, I think it was ready for a new transport anyhow... The plastic gears in the old one are very worn out and I think the laser was getting a bit weak too.
I've lubed many transports with fine results. I guess somehow I dripped some oil right into the transport.
Either way, I think it was ready for a new transport anyhow... The plastic gears in the old one are very worn out and I think the laser was getting a bit weak too.
Even a drop of oil is too much. Best is to put one drop on some cloth and lubricate it this way if it is really necessary.
Only use grease/oil ( grease is preferred over oil ) on the plastic gears that's compatible with plastics. Silicone grease is appropriate. I always hesitate lubricating plastic gears since I learnt as a mechanic that plastic gears only need cleaning, not lubricating.
The chrome rods where the laser runs on are to be cleant with a cloth with some alcohol and afterwards you can put a very tiny drop of teflon oil or "sewing machine oil" on a cloth and lubricate the rods like this.
When oil comes into the laser it is over, but you experienced this yourself now.
Only use grease/oil ( grease is preferred over oil ) on the plastic gears that's compatible with plastics. Silicone grease is appropriate. I always hesitate lubricating plastic gears since I learnt as a mechanic that plastic gears only need cleaning, not lubricating.
The chrome rods where the laser runs on are to be cleant with a cloth with some alcohol and afterwards you can put a very tiny drop of teflon oil or "sewing machine oil" on a cloth and lubricate the rods like this.
When oil comes into the laser it is over, but you experienced this yourself now.
I see your point....
I did clean the chrome rod like you said and used sewing machine oil... That was really the only sticky part. I didn't bother too much with the plastics though.... Still, I was using a fairly bulky oil can and I figure that maybe a bit dripped down the side of the can while I wasn't looking.
Anyway, it's not really the end of the world. I hear that the transport in these is quite popular and they sell for somewhere between 15 and 30 bucks USD. I can afford that pretty soon....
I did clean the chrome rod like you said and used sewing machine oil... That was really the only sticky part. I didn't bother too much with the plastics though.... Still, I was using a fairly bulky oil can and I figure that maybe a bit dripped down the side of the can while I wasn't looking.
Anyway, it's not really the end of the world. I hear that the transport in these is quite popular and they sell for somewhere between 15 and 30 bucks USD. I can afford that pretty soon....
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