Sunday, February 24, 2019

Fixing DENON DCD-510AE CD player


While visiting friends I heard their complaints that they have a CD player which keeps on resetting. It wasn't able to eject the CD (there was one inside). On the display it was continuously saying "READING". From time to time this player was able to start playback but it ceased when pressed "next". I was told that the CD module was already replaced twice with no result. My first thought was that it has got to do something with supply voltage. Circuit diagram is easy to find on https://www.manualslib.com/manual/1115299/Denon-Dcd-510ae.html#manual .
I started by checking 5V and 8V net, see sample trace below. I also observed (you have to believe me because I have no waveforms for that) that 8V was dropping to lowest values when a skip track or eject button was pressed. Spinning the CD loaded the 8V and 5V net significantly too.
Blue trace i 8V and yellow is 5V.
5V and 8V are both generated by linear regulators and it is obvious that 8V is overloaded so much that 5V falls below reset threshold. I inspected C914, IC93 and C916, they appear fine. I measured current consumption on 8V (approx. 1A max) and supply transformer voltage. According to my crude calculations C914 value is way too low, and I believe that the power supply is calculated without margin. I don't have 22000uF capacitor and I didn't want to order one but I realized that I have a 230V to 5V 1A switching mode power supply and keeping in mind that the main load on the 8V net is the 5V regulator I decided to add an additional power supply to provide 5V from another supply.
I removed IC94 and connected additional power supply (see yellow rectangle) parallel to C917. This new power supply is connected in parallel to the primary winding of the main transformer of the CD player T901
It's not ideal, I could try experimenting with the original power supply and low ESR high capacity alternatives for the C914 but I had an extra switching mode power supply lying around so I used it. It works just fine.

4 comments:

  1. Thank you for the walk through of this problem. I had the same problem and looked at the supply too. While I hadn't an extra supply lying around, I opted for replacing D902 and D903 with a RURP820 (with lower Vf) to give an extra 0.5V to keep the supply above the drop-out voltage of the 7808.

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  2. Hi Arek,
    thanks to your help, i have fixed the same cd player with the same trouble. I've done the same repair than Palle and the player came back to life.
    What can i say? thks for sharing.

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  3. Dobra robota Arku. Nie mogłem rozkminić w czym problem, bo bez płyty tacka się wysuwa, z płytą już nie.
    Dziękuję.

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  4. Solutia de scrisa de Palle este ieftina, rapida si functionala. Multumesc!

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