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electronicsguy, Engineer
Category: Recorders and Players
Satisfied Customers: 664
Experience:  Worked on these instruments for over 15 years.
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OMS 7A ii single CD player powers up but tray does not

Customer Question

OMS 7A ii single CD player powers up but tray does not function what possible problem?
Submitted: 1 year ago.
Category: Recorders and Players
Expert:  electronicsguy replied 1 year ago.

Hi, can you check the following: when you press the button to open the tray, do you hear a motor running?

Customer: replied 1 year ago.
no motor response, I'm an experienced tech w/over 30+ years in satellite receiver repair, suspect bad caps or logic problem
Customer: replied 1 year ago.
This is an original untampered unit of known origin worked to play a disk, ejected disk but tray did not and will not close on its' own since last play.
Expert:  electronicsguy replied 1 year ago.

Thanks for your response to listen to the motor you have put your ear close to the unit then press the open button. If you have done so, then we have electronics problem. It is rare that electronics go bad. I think it might be a belt problem.

Can you take the top cover off and visually inspect the tray belt? Let me know the results.

Customer: replied 1 year ago.
Have already done this, no motor action. Center spindle turns slightly when power is turned on or off but pressing the open close tray button does not turn the smaller motor to the touch. like it is not getting any power.
Customer: replied 1 year ago.
no measurable volts on motor tabs, AC or DC
Customer: replied 1 year ago.
no motor volts on tabs turning unit on or off
Expert:  electronicsguy replied 1 year ago.


Can you disconnect one of the motor power terminal and measure motor resistance. Also on the motor they might have info about power ratings for the motor. Using power formulary you can calculate winding resistance. The ohmeter should read close to calculated value.

If this is not possible apply a small DC voltage a cross the motor 5v suggested and see if it will turn. To avoid damage, you should have one of the terminal disconnected and system should be powered off.

Customer: replied 1 year ago.
tray opens and closed with +/- 5v, don't think it is getting any thing out of the op amp of U104
Expert:  electronicsguy replied 1 year ago.

So this confirm that the motor and belt are ok. The last thing you can is to find the op amp and replace it or bypass the switch and manually use +/-5 volts to open and close the tray.

Expert:  electronicsguy replied 1 year ago.

Any luck on your end?

Customer: replied 1 year ago.
not replaced the op amp u104, does not seem to get a key pulse from the microprocessor, looks like the signal should go hi/low to change the state of the voltage supplied. checked the state from the front switch for eject and it goes low when pressed, so it is getting into the processor.
Expert:  electronicsguy replied 1 year ago.

So, if the key gets signal from the microprocessor, then when you press or the second time, the polarity should change. Is that the case, what voltage are you measuring at the switch?

Customer: replied 1 year ago.
Red lead of ju 403 is 1.35 v. On the pins of u 104 : pin 1 =9.06V, pin 2= 2.3 V, pin 3 = 2.6 v, pin 4= -11.50, pin 5=0, pin 6 = 0, pin 7=0, pin 8= 10.9V. Pins 6 and 7 don't change state with key press, am assuming(bad practice) that pin 6, and/or pin 7 should change state when eject is pressed which affects Q109 and Q110 to change polarity and feed the +/-5 volts to the motor, pin 2 of ju 104. CD plays fine, just the tray doesn't work. Suspecting maybe the microprocessor at this point.
Expert:  electronicsguy replied 1 year ago.

I think you have a problem where the power should change polarity unless there is a gear system that moves the tray. I would probably think that we have a much bigger problem that what I thought it was. Can you tell me how much space do you have on inside? You can build a circuit that can perform the same functions and use a relay to perform the change over. You can either use the open function or the close function but not both. Is this something you would like to explore?

Customer: replied 1 year ago.
why do this if only need to supply a + voltage to open the tray, just hot wire the open close switch to open only and manually close the tray.
Expert:  electronicsguy replied 1 year ago.

You do need +/- to open and close. It is difficult to swap both terminals athe each instance without using complicated hardware