Onkyo DV-CP704 will not turn on.
I was recently given a DV-CP704 with similar problems. I fixed my problem, well sort of - read on. I did not have a schematic so I decided to start by checking power supply voltages. I noticed a fluctuating voltage on the K0 pin. This is located on a connector on a circuit board under the disk drawer, and the connector services a cable harness coming from the front panel controls. NOTE: before removing or installing connections, I unplugged the player power cord first then plugged it back in. Not knowing where the voltage was originating from I decided to unplug the front panel connector. The voltage on the K0 pin of this circuit board stabalized at +5 volt and was not fluctuating. I traced out where this pin went to the front panel and among other places it went to the power on/off switch and the drawer open/close switch. I restored the front panel connection and while monitoring the voltage on K0 I noted that when I press either the power on/off button or the drawer open/close button this voltage would go low, not to zero but to some lower voltage but when I released the button the voltage would once again fluctuate. While watching the voltage, if I pressed the power on button when the voltage was near +5 volts, the unit would turn on and off. To me it seemed that this voltage should be stable at +5 volts with no button press and should go low only when there was a button press. Next I decided to unplug the harness that went to the drawer open/close circuit board. The voltage on K0 was still fluctuating so I restored this connection. Then I unplugged the harness that went to the power on/off circuit board. AHHHHH, the voltage on K0 was now steady. I removed this small power switch circuit board. Not much to it, some switches, capacitors, LED etc. I did not see any obvious issues with the circuit board. I decided that either the power switch or the small capacitor across the power switch contacts were breaking down causing the K0 voltage to fluctuate. I decide that the power switch was the easiest to remove so I unsoldered and removed it, plugged the board back in. Now I can power on and off by jumpering where the switch was. The K0 voltage is steady and all other buttons work properly. I assumed that the problem was the power switch. I checked the switch with a high impedance Fluke ohmmeter but to my supprise I did not see any problem with the switch. I decided to reinstall the power switch to recreate the problem however now everything is working normally. I can only assume that the heat I applied to the switch during unsoldering somehow fixed the switch by melting or burning away the problem. In my case it was the power switch however all of the tactile switches appear to be the same type so if there is an inherent problem with these switches, soldering or cleaning I would assume it could have been any one of them. If you want to give this a try, remove the cover, remove the 3 screws that secure the front bezel on the bottom of the player. There are two small clips that need to be lifted to release the front bezel so it can be removed from the player and flipped down to gain access to the back while it is still attached electrically. Attach your voltmeter negative lead to the main chassis (ground) and with the positive lead measure the voltage on the power switch pins. One pin is ground so it should read zero or close to it. The other is the K0 signal and it should be at +5 volts until the button is pressed. I don't know about any of the other buttons but they may also operate in a similar fashion. I hope this may help some of you.
Dec 09, 2007 |
Onkyo DV-CP704 DVD Player