I bought a non-working Cyrus DAD3 player that didn't read discs. I replaced the laser unit, Philips CDM12.6, so now it reads discs but there is another problem.
When the power switch is turned on, the sled moter sends the sled all the way forwards so the gears make a noise (the limit contacts are closed by the sled). The only way to stop this is to turn the switch off/on about 3 times (is that a clue to the cause?) and if the player is left powered on, and the front button used to put it into standby mode, then powered on, it is fine - so one step forward one back.
I am not sure if this has been introduced as when testing for it not reading discs, I powered it on with the switch, then would eject the disc, skip tracks etc, to see if it would read, in other words the unit was switched on by the main switch once, then the standby button used.
Now it's gonna get a bit more technical.
The sled motor has worm drive to a cog that meshes with a linear gear on the laser unit. 2 wires to this motor come from a TDA 7303 device (Dual BTL power driver) that is driven by SAA7345 (CMOS digital decoding IC with RAM for Compact Disc ).
The driver has a 9 V power supply from a LM317T which has a slow start circuit comprising PNP transistor and C-R (10uF and 220k). The transistor grounds the 'adjust' on LM317T, so output is low, but as the capacitor on the transistor's base is charged through the resistor, the PNP turns off so the output voltage on the LM317T stays fixed at 9V. (multisim shows it takes 1 sec to go from 2 to 9 v)
So I am thinking that when the main switch powers all the electronic components, the SAA7345 has set the pins to run the motor but the slow start is there to keep the voltage from the LM317 low so the motor doesn't turn.
To fix this, I soldered a 22 uF capacitor in parallel to increase the time before the LM317 reaches full power but that did not solve it. I checked the 220k is ok.
I am now thinking that because to stop the motor running requires turning the main switch off/on multiple times, it is as if a capacitor is gradually being charged on each power on and the CPU is doing its initialisation task at the same time, eventually the event the CPU uses to stop the motor has reached its final value due to the capacitor being charged so any further on/off no longer send the motor running (does that make sense?) After letting this capacitor to discharge by leaving the CD player powered off for a few minutes, the problem returns.
Right now I am a bit stuck hence looking for any suggestions - somebody may have played with the same CD player or have had a similar problem.
All is not lost as I do have a second working unit that I can compare to. ... and maybe time to get the 'scope on it.
When the power switch is turned on, the sled moter sends the sled all the way forwards so the gears make a noise (the limit contacts are closed by the sled). The only way to stop this is to turn the switch off/on about 3 times (is that a clue to the cause?) and if the player is left powered on, and the front button used to put it into standby mode, then powered on, it is fine - so one step forward one back.
I am not sure if this has been introduced as when testing for it not reading discs, I powered it on with the switch, then would eject the disc, skip tracks etc, to see if it would read, in other words the unit was switched on by the main switch once, then the standby button used.
Now it's gonna get a bit more technical.
The sled motor has worm drive to a cog that meshes with a linear gear on the laser unit. 2 wires to this motor come from a TDA 7303 device (Dual BTL power driver) that is driven by SAA7345 (CMOS digital decoding IC with RAM for Compact Disc ).
The driver has a 9 V power supply from a LM317T which has a slow start circuit comprising PNP transistor and C-R (10uF and 220k). The transistor grounds the 'adjust' on LM317T, so output is low, but as the capacitor on the transistor's base is charged through the resistor, the PNP turns off so the output voltage on the LM317T stays fixed at 9V. (multisim shows it takes 1 sec to go from 2 to 9 v)
So I am thinking that when the main switch powers all the electronic components, the SAA7345 has set the pins to run the motor but the slow start is there to keep the voltage from the LM317 low so the motor doesn't turn.
To fix this, I soldered a 22 uF capacitor in parallel to increase the time before the LM317 reaches full power but that did not solve it. I checked the 220k is ok.
I am now thinking that because to stop the motor running requires turning the main switch off/on multiple times, it is as if a capacitor is gradually being charged on each power on and the CPU is doing its initialisation task at the same time, eventually the event the CPU uses to stop the motor has reached its final value due to the capacitor being charged so any further on/off no longer send the motor running (does that make sense?) After letting this capacitor to discharge by leaving the CD player powered off for a few minutes, the problem returns.
Right now I am a bit stuck hence looking for any suggestions - somebody may have played with the same CD player or have had a similar problem.
All is not lost as I do have a second working unit that I can compare to. ... and maybe time to get the 'scope on it.
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Not any closer to fixing it but I understand why increasing the slow start for the 9v supply has no effect. The motor turns if there is a difference on the outputs of the BTL driver, regardless of what the supply voltage is (which is gradually ramping up to 9v). Need to look at the 2 inputs to see what can cause that.
Still not figured why turning off/on the main switch stops the problem happening.
Still not figured why turning off/on the main switch stops the problem happening.
First thing I would do is make it mechanically safe by removing a gear or dropping the sled motor so that it doesn't chew through the gears. You can then pull and push the sled by hand to see if the end switch is OK.
Beyond that it is a case of methodical fault finding. Many Philips nased players do not take kindly to being recapped (if that has happened in its past) and different value parts being fitted. The sequencing of rails can be very important.
Beyond that it is a case of methodical fault finding. Many Philips nased players do not take kindly to being recapped (if that has happened in its past) and different value parts being fitted. The sequencing of rails can be very important.
Back to this.
In response to the above. The strip with the linear teeth is spring loaded so the gears won't get chewed.
I bought and fitted a replacement laser (CDM12) as it wasn't reading CDs and STUPIDLY did not compare the old part with the new, the result being the sled motor stopped running. The new ribbon cable had fewer tracks, so I figured I had shorted the outputs from the BTL driver.
I replaced the BTL driver (first attempt with an SMD package) so the player now reads discs but has the 'power up' problem as below.
From cold, as in not powered for 1/2 hour or more, turning it on with main switch, the LCD shows it goes through its initialisation process which is basically cycling though on all the segments in the LCD ending with going into standby mode. Pressing standby button, it attempts read a CD but fails; 00 on the display.
I leave it like in standby mode for 10 minutes, then pressing the standby to be on, it will read the CD every time. The problem described in the original post is less frequent but seems to occur when turning off/on the mains switch when it is 'cold'.
I am not sure what is causing that but am guessing it may be heat related, so my next step is to leave it powered off and warm up parts of the circuit board with a hair dryer to see which area is responsible.
In response to the above. The strip with the linear teeth is spring loaded so the gears won't get chewed.
I bought and fitted a replacement laser (CDM12) as it wasn't reading CDs and STUPIDLY did not compare the old part with the new, the result being the sled motor stopped running. The new ribbon cable had fewer tracks, so I figured I had shorted the outputs from the BTL driver.
I replaced the BTL driver (first attempt with an SMD package) so the player now reads discs but has the 'power up' problem as below.
From cold, as in not powered for 1/2 hour or more, turning it on with main switch, the LCD shows it goes through its initialisation process which is basically cycling though on all the segments in the LCD ending with going into standby mode. Pressing standby button, it attempts read a CD but fails; 00 on the display.
I leave it like in standby mode for 10 minutes, then pressing the standby to be on, it will read the CD every time. The problem described in the original post is less frequent but seems to occur when turning off/on the mains switch when it is 'cold'.
I am not sure what is causing that but am guessing it may be heat related, so my next step is to leave it powered off and warm up parts of the circuit board with a hair dryer to see which area is responsible.
A few years ago I got a Marantz CD63 for £20 and went about all the mods outlined in the threads for the 63/67 on here. It was fine in warm weather but when the room dropped to around 15 degrees it would not read a disc. Using a blow heater to warm up the sled and some of innards for a few minutes cures the problem.
I warmed up the base plate for a couple of minutes and it does very much look like it is heat related.
Next step is to remove the base plate and heat up an area, gradually reducing its size, until the component is identified..... that may take some time.
I'm wondering if getting some freezer spray would be quicker.?
Next step is to remove the base plate and heat up an area, gradually reducing its size, until the component is identified..... that may take some time.
I'm wondering if getting some freezer spray would be quicker.?
It's very difficult to diagnose problems like this at a distance. Deteriorated caps in the power supply can give odd issues but a scope check of rails when in the faulty state should prove/disprove any suspects.
If it attempts to read a CD (as in spins up to speed normally) then I would look at the RF in that faulty state and compare such things as amplitude and overall 'Q' or quality compared to when it works normally.
If it attempts to read a CD (as in spins up to speed normally) then I would look at the RF in that faulty state and compare such things as amplitude and overall 'Q' or quality compared to when it works normally.