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Old 20th March 2017, 09:46 PM   #11
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I think that you are looking for "radial offset" and that the "focus offset" refers specifically to the voltage offset on the focus motor driver output between no-disc and reference disc values.
The universal way of setting the radial offset on Philips CD304-based machines is without the jig on the above image. Basically you will want to trigger the oscilloscope with 650Hz fed into radial mechanism, probe between the output of the RF amplifier circuit on CD drive board and ground and again adjust for the minimum amplitude modulation.
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Old 21st March 2017, 10:40 AM   #12
Salar is offline Salar  Germany
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Thanks a lot! So i trigger the scope with the 650hz wobble signal and measure Eyepattern, correct?
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Old 21st March 2017, 03:46 PM   #13
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My apologies, there is a bit of confusion among different terminologies used by different manufacturers. The sequence of alignment I described applies to CDM1-based players using more modern TDA servo circuits where the FO trimpot is not even present. The two adjustments I suggested are actually for the focus gain. However, two SMs I checked explicitly say "factory aligned, not to be changed” for the FO, while the common wisdom is to leave the trimpot in its original position or, if moved or trimpot changed, to place it in the middle position.
The adjustment of the radial motor offset voltage is done in the service mode. Basic adjustment is to place the swing arm in the middle position and correct the voltage on radial motor driver output to minimum. This is done in the service mode. There are several programme steps in which the symmetrical inward and outward deflection of swing arm is observed (it also serves to compensate for the spring-loaded resistance of the flat cable). The last programme engages the player in PLAY and the arm follows the track but without the processor.
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Old 25th March 2017, 02:19 PM   #14
Salar is offline Salar  Germany
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There are several programme steps in which the symmetrical inward and outward deflection of swing arm is observed (it also serves to compensate for the spring-loaded resistance of the flat cable).

I think the compenation is neglecteable. When I mechanically aligned the swing arm,
with the swing arm in the first track, the flat cable touched my index finger. I was urprised how much force was needed to make the laser skip while pressing the finger on the cable. I also think that a lot of alignment depends on the mechanical side.
For fellows stumbling over this thread:

Philips CDM-1 swing arm alignment
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