Lets take a step back and look at the info we have.
Firstly I don't know how the data sheet values for Vh and Vl are to be interpreted. So we still don't know for sure what the typical RF level is. The picture attached shows how most service manuals show the level. And these amplitudes are common across many makes and models but maybe this one is an exception.
The correct level is of utmost importance. Going lower will not damage anything, going higher could over drive the laser.
The preset pot is normally on the pickup itself although a few players have it on the main PCB.
Do you have any service info on the player.
Firstly I don't know how the data sheet values for Vh and Vl are to be interpreted. So we still don't know for sure what the typical RF level is. The picture attached shows how most service manuals show the level. And these amplitudes are common across many makes and models but maybe this one is an exception.
The correct level is of utmost importance. Going lower will not damage anything, going higher could over drive the laser.
The preset pot is normally on the pickup itself although a few players have it on the main PCB.
Do you have any service info on the player.
Attachments
Executive decision.
This is really hard without having the player to see and work on and I don't want to give you misleading or wrong info
Maybe a close up clear picture of the component side of the PCB might help identifying adjustments. If there is no laser power preset on the pickup then it will be on the main PCB... probably... unless it's a fixed factory setting or adjusted via software (unlikely).
If there is a Focus Bias preset then you can see if adjusting that makes the RF any clearer or larger in amplitude.
Other tests unrelated to the laser are to monitor the DC voltage across the sled motor and make sure it stays at a low value when in play. The motor should just nudge along constantly. If the sled sticks the voltage will gradually increase until friction is overcome and then the sled jerks forward causing jumping or loss of "lock" and the player throws a fit.
This is really hard without having the player to see and work on and I don't want to give you misleading or wrong info
Maybe a close up clear picture of the component side of the PCB might help identifying adjustments. If there is no laser power preset on the pickup then it will be on the main PCB... probably... unless it's a fixed factory setting or adjusted via software (unlikely).
If there is a Focus Bias preset then you can see if adjusting that makes the RF any clearer or larger in amplitude.
Other tests unrelated to the laser are to monitor the DC voltage across the sled motor and make sure it stays at a low value when in play. The motor should just nudge along constantly. If the sled sticks the voltage will gradually increase until friction is overcome and then the sled jerks forward causing jumping or loss of "lock" and the player throws a fit.
Thanks for taking the trouble to post the pics. The pots are not labelled here either as to function
I spent quite a while looking at more data on the LA9200 but nothing is clearly identifiable as to its absolute function. Your player seems to use the IC in dual supply mode.
It appears that there is NO laser power control built into the IC. That means that the laser power is preset on the pickup and with no preset present is non adjustable. So that seems to take that out of the equation.
I can only suggest (and this is up to you... no guarantees) that the function of the presets be determined experimentally.
That goes against everything I would normally recommend so it's up to you
You need to first monitor the RF and adjust one at a time to determine function and then return it to the same physical position before turning another.
1. The focus bias pot will alter the clarity and amplitude of the RF signal. It has to be set for sharpest and highest level.
2. Focus Gain. May have no obvious effect on the RF but if you listen carefully to the "white noise" produced by the pickup itself it may increase as gain turned up. The focus pots seem to be the ones connected with pins 33 and 31.
3. Tracking gain. May show no obvious effect when turned. The correct way to adjust (and determine which is tracking gain) is to put the scope on the tracking error output from the IC and turn the pot. As the gain is increased a low frequency fundamental wave will appear. The correct gain point is just at the point of this wave appearing.
4 EF balance. Is performed by monitoring the tracking error wave and performing "track jumps" and adjusting for symetrical "above and below" a notional centre line.
Before doing any of this make sure ALL mechanical issues are attended too. Do the checks I mentioned on the sled motor.
Look up Sony service manuals for the CDP101 and Sony D50 mk1 as these give clear instructions on what to expect when adjusting a player. The controls and there effect are similar in most players.
Remember the warning though... no guarantees and be under no illusions.
I spent quite a while looking at more data on the LA9200 but nothing is clearly identifiable as to its absolute function. Your player seems to use the IC in dual supply mode.
It appears that there is NO laser power control built into the IC. That means that the laser power is preset on the pickup and with no preset present is non adjustable. So that seems to take that out of the equation.
I can only suggest (and this is up to you... no guarantees) that the function of the presets be determined experimentally.
That goes against everything I would normally recommend so it's up to you
You need to first monitor the RF and adjust one at a time to determine function and then return it to the same physical position before turning another.
1. The focus bias pot will alter the clarity and amplitude of the RF signal. It has to be set for sharpest and highest level.
2. Focus Gain. May have no obvious effect on the RF but if you listen carefully to the "white noise" produced by the pickup itself it may increase as gain turned up. The focus pots seem to be the ones connected with pins 33 and 31.
3. Tracking gain. May show no obvious effect when turned. The correct way to adjust (and determine which is tracking gain) is to put the scope on the tracking error output from the IC and turn the pot. As the gain is increased a low frequency fundamental wave will appear. The correct gain point is just at the point of this wave appearing.
4 EF balance. Is performed by monitoring the tracking error wave and performing "track jumps" and adjusting for symetrical "above and below" a notional centre line.
Before doing any of this make sure ALL mechanical issues are attended too. Do the checks I mentioned on the sled motor.
Look up Sony service manuals for the CDP101 and Sony D50 mk1 as these give clear instructions on what to expect when adjusting a player. The controls and there effect are similar in most players.
Remember the warning though... no guarantees and be under no illusions.
Hi there Hans,
Burning your own CD's is a great way to get audio signals if you haven't any test gear such as signal generators.
When using a CD for player alignment it is the reflectivity of the disc that is important. The content of the disc has no effect on the results and the RF always looks the same.
A CDR or CDRW is really poor compared to a commercial disc.
Try it and see by looking at the RF
Burning your own CD's is a great way to get audio signals if you haven't any test gear such as signal generators.
When using a CD for player alignment it is the reflectivity of the disc that is important. The content of the disc has no effect on the results and the RF always looks the same.
A CDR or CDRW is really poor compared to a commercial disc.
Try it and see by looking at the RF
It's not that sort of fault really. That won't tell you anything.
From what you say (looking back to the start), the not reading TOC could be mechanical. The pickup has to be in the correct position and if it's out a little bit then that can cause issues. It usually depends on the physical position of a limit switch to tell the servo when its at the end.
Also the spindle motor (platter motor) could be temperamental. Unofficial fixes are disconnecting the spindle motor and applying 9 volts for a few seconds to spin and clean up the commutator.
And skipping through a track could be sled related. Does it skip at the same point on the disc if its left to play ?
You must do the test of measuring DC volts across the motor when playing to make sure the sled isn't sticking. If the voltage is around 0.2 volts say (and it is low normally) and then it suddenly goes 0.3, 0.4, 0.5 and so on and then jumps and the voltage falls back to normal that is because the sled was sticking.
All these have to be confirmed before going to deep looking for an electronic issue.
A lot of things have to come together and work correctly in a CD player and all must be checked.
From what you say (looking back to the start), the not reading TOC could be mechanical. The pickup has to be in the correct position and if it's out a little bit then that can cause issues. It usually depends on the physical position of a limit switch to tell the servo when its at the end.
Also the spindle motor (platter motor) could be temperamental. Unofficial fixes are disconnecting the spindle motor and applying 9 volts for a few seconds to spin and clean up the commutator.
And skipping through a track could be sled related. Does it skip at the same point on the disc if its left to play ?
You must do the test of measuring DC volts across the motor when playing to make sure the sled isn't sticking. If the voltage is around 0.2 volts say (and it is low normally) and then it suddenly goes 0.3, 0.4, 0.5 and so on and then jumps and the voltage falls back to normal that is because the sled was sticking.
All these have to be confirmed before going to deep looking for an electronic issue.
A lot of things have to come together and work correctly in a CD player and all must be checked.
Sled position at disc start is difficult because there is nothing to measure physically. Make sure any microswitches are undamaged and the "leaves" straight and not bent.
I would look to fixing the skipping first because that may well be connected to the not reading TOC and should be easier to fix.
Do the sled check first and then repeat it using the same CD (use a long disc) and keep a note of where in the disc the problem occurs.
I would look to fixing the skipping first because that may well be connected to the not reading TOC and should be easier to fix.
Do the sled check first and then repeat it using the same CD (use a long disc) and keep a note of where in the disc the problem occurs.
