I recently picked-up a Philips CDC486 six discs changer from a flea market. Sound-wise it is a pretty standard Philips of its time with CDM 4/20 and TDA1543 as DAC. It appeared to have only mechanical problems and I tried to took care of that. Before embarking in the restoration, I tested if the CD player part was actually working and in service mode it successfully locked focus (phase 1), track (phase 2) and disc rotation (phase 3); after one minute it then started to play music and I was happy and continued restoring it.
After stripping down, cleaning and fixing the cd-changer side, the player side appears to no longer works: on power on the disc spindle starts rotating at high speed and everything appears to be stuck. I am able to load disc and in that case disc rotation is slowed down and the pick-up seems to lock to the track, but there is no play back.
I tried again the service mode and this time I'm greeted with what is shown in the attached pic. I have retouched all possible solder joints, I have checked connections and voltages and everything appears to be correct. I have read else where that behaviour might be caused by a faulty decoder chip SAA7210: is that the only option ?
What could have I done wrong to kill it ?
thanks
further note: the display works correctly in normal mode, so it is not a problem with the display or the main CPU itself
After stripping down, cleaning and fixing the cd-changer side, the player side appears to no longer works: on power on the disc spindle starts rotating at high speed and everything appears to be stuck. I am able to load disc and in that case disc rotation is slowed down and the pick-up seems to lock to the track, but there is no play back.
I tried again the service mode and this time I'm greeted with what is shown in the attached pic. I have retouched all possible solder joints, I have checked connections and voltages and everything appears to be correct. I have read else where that behaviour might be caused by a faulty decoder chip SAA7210: is that the only option ?
What could have I done wrong to kill it ?
thanks
further note: the display works correctly in normal mode, so it is not a problem with the display or the main CPU itself
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I did some more investigation, but come to nothing conclusive: the unit has two microProcessor, one controlling the disc changer side and another one controlling the CD player side. They both have a reset signal and it goes low on power on as expected. Then starts the anomaly: on the I2C bus connecting the two uC there is supposed to be activity, but instead both wires are "high" which is the start-up condition. The MUTE signal sent to the decoder SAA7210 is "high" while it should be "low". It basically seems the uC managing the CD player is stuck on start-up and does not continue.
I do not have an oscilloscope to check the clock signals...
Any suggestion ?
I do not have an oscilloscope to check the clock signals...
Any suggestion ?
Thanks, yes i read about the ground planes problems, but this board has solder joints only on one side and the ground planes are grounded with jump wires whose two ends are soldered on the "solder side" of the board and the wire middle is soldered onto the ground plane on the other side. There are no via's between the two sides of the board (which are more likely to break)
Do you have an idea what should i check to verify a ground plane problem ?
Do you have an idea what should i check to verify a ground plane problem ?
I checked again all grounding points, but being made with wires, they are fine, all pins that are supposed to be ground are connected. I re-touched all solder joints in IC's too, but behavior has not changed.
I am out of option, the problem of this player is beyond my skills, and the service manual offers no trouble shooting for such fault on the logic board, they were not expecting this kind of problems. Beside a few indications on reset and clock, there is no other mention of voltages and values on all IC's, or the expected waveform on start-up. I guess they would just replace the board and calli it a fix.
I am out of option, the problem of this player is beyond my skills, and the service manual offers no trouble shooting for such fault on the logic board, they were not expecting this kind of problems. Beside a few indications on reset and clock, there is no other mention of voltages and values on all IC's, or the expected waveform on start-up. I guess they would just replace the board and calli it a fix.
All supply voltages are there (+12, +/- 10, +/- 5); to fix the mechanical problem i had to basically disconnect everything; i suspected too a bad connection, but the cd changer side "works" fine, the display is fine (when in normal mode), it is just the player section that is stuck.
It worked before, but only in service mode, in normal mode all mechanical problems prevented playing any CD.
It worked before, but only in service mode, in normal mode all mechanical problems prevented playing any CD.
It can be bad capacitors as well but without measurement equipment it will be hard to fix the player. But as said before i think it is a connection somewhere. Either a wire or on the pcb.
I have replaced three Philips caps (axial cyan coloured caps) which I know were bad (47 uF measuring on average 18 uF) but it did make no difference. I checked the reset circuit (a cap charged through a resistor) and it is fine (high on power up, low within a second) . Other electrolytic caps are from better brands and they are on power rails (which are fine). There are problems in the logic side of the CD player section, the uP does not properly start-up and does not communicate through I2C bus with the other uP.
Connections to the boards seems fine:
Connections to the boards seems fine:
- connections to display and keyboard seems fine as both display and keyboard work
- connections to the motors and sensors in the changer sections are fine because it loads and change disc succesfully
- connections to the power supply are fine as all voltages are there.
- connections to the CDM 4 are fine as spindle motor rotates and, if a Cd is present in the tray, the pick-up actually locks on the track (disc rotation slows down and pick-up locks focus and tracking)