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Onkyo C-707CHX CD Changer - Drawer will not open - SOLVED

Discussion in 'Digital Sources' started by kstinmb, Jul 15, 2017.

  1. kstinmb

    kstinmb New Member

    Messages:
    8
    For several years I have been trying to trouble-shoot the Onkyo C-707CHX 3-disc changer. It is regularly offered on the Bay and elsewhere in seemingly good condition, except the drawer will not open. Motor and other noises can be heard, but it just won’t open.

    On a couple I found that the rubber drive belts had stretched and lost their elasticity from age and simply could not turn the complicated mechanism. But on most even new belts didn’t solve the problem.

    By comparing a functioning unit to my dud, I found that there’s a drive shaft from the main pulley which has plastic/nylon gears pressed on each end. Over time, the gears have loosened from the steel shaft and just spin under any load. Plus, on one end the gear had actually split and thus lost its grip.

    Replacement parts are long out of stock for this player, including small parts and the entire CD changer/player cassette. So this one is headed for the electronics recycle bin or I’ll offer it up for someone who needs a new display or front panel. It’s frustrating to have to toss what looks like perfectly good gear for lack of a small part.

    Onkyo C-707CHX 3-Disc CD Changer
    [​IMG]

    Main pulley, remove rubber belt, remove the c-ring
    [​IMG]

    Main pulley and drive shaft. Remove pulley.
    [​IMG]

    The pressed-on drive gear has loosened and just spins on the shaft under load.
    [​IMG]

    This gear has split and lost its grip as well.
    [​IMG]

    Comparing operation of functioning unit (left) and problem child.
    [​IMG]

    It’s a shame to toss this out.
    [​IMG]

    Regards,
    -stephen
     

     

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  2. Camsnparz

    Camsnparz New Member

    Messages:
    10
    For about 15 C-707 I have repaired, I run into 2 times of these broken gears, exactly the same location.
    IMG_2762.JPG IMG_2759.JPG
    If you have a scavenger unit, you may take this part from that and make the unit you need to fix working again. Otherwise, you can try what I did:

    I flatted 2 #5 spring washers, it needs to be very flat, or the mating gear will be chewed by it.
    IMG_2755.JPG IMG_2756.JPG IMG_2758.JPG IMG_2757.JPG

    Force the washers onto both end of the broken gear, aligning the open of the spring washer to the opposite of the crack on the gear.
    IMG_2764.JPG

    Press the gear back onto the shaft, while sliding in the larger gear with it. If not do at the sametime, the larger gear will not slide in, since the spring washer blocks it.
    IMG_2766.JPG

    Put the gear frame back to the disk drive body. There is no way this gear be broken again.
    IMG_2767.JPG

    I have plenty of these spring washers, if anyone want to try, let me know and I can send you a few.
     
  3. cpt_paranoia

    cpt_paranoia Well-Known Member

    Messages:
    942
  4. Camsnparz

    Camsnparz New Member

    Messages:
    10
    Yes this one is a bit unusual. Onkyo used 0.4 Modulus in their design of this player, not the popular and cheap 0.5 modulus gears now a days all over ebay and Ali Express. Search for "0.4M12T nylon gear" on Google, you will find how hard to find them. Factory parts were long gong even you have the part number from the service manual. Over the years, I only run into once a company at Hong Kong carried 0.4M12T for retail, though still not the exact length but you may cut it to fit, but minimal order was $25 plus shipping. Better off to buy a used C-707 from ebay and hope that this gear is usable. Or came up with a creative way to fix it at little or no cost.
     
    Last edited: Jun 17, 2018
  5. cpt_paranoia

    cpt_paranoia Well-Known Member

    Messages:
    942
    I forgot the modulus... How inconvenient of them...
     
  6. Camsnparz

    Camsnparz New Member

    Messages:
    10
    Yeah, not everyone will go down to this level of details. Actually, trouble shooting the broken gear shouldn't stop at fix or replace the little gear. There must be a reason for why this gear broke, and it may not be the quality or design of the gear. Guess what is the most logical cause? Stress - extra stress. where it came from? The mechanisms this gear driving for has other abnormal issues. If I don't find and fix those causes, this gear holds up load better new, and something else will break.
     

     

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  7. cpt_paranoia

    cpt_paranoia Well-Known Member

    Messages:
    942
    My guess would be mechanical or environmental stress cracking. Interference fit and that shaft knurling raising a stress concentrator, or some lubricant, or combination of the two.

    And time...
     
    Last edited: Jun 19, 2018
  8. Armozo

    Armozo New Member

    Messages:
    1
    Hi, thanks for explaining how to fix the gear that was split. How did you fix the other gear?
    Thanks


     
  9. Camsnparz

    Camsnparz New Member

    Messages:
    10
    Hi Armozo, I guess you mean how do I fix the loose umbrella gear on the other end of the shaft? Actually, none of them loosen in my cases. When one of the two pressed-on gears on one shaft became loose, no more torque can be applied to the other anymore, therefore the other one will never break. The smaller spur gear is obviously the weak one and almost always break first. However, if the umbrella gear ever cracks on its collar, my way to fix it will still be clamping. If it cracks through the teeth, no fix I can think of, no effective nylon glue I am aware of. If it just stripped it's knurling, I may try a drop of crazy glue between the gear hole and the shaft. Hope this helps.
     
    Last edited: Sep 24, 2018
    Armozo likes this.
  10. Camsnparz

    Camsnparz New Member

    Messages:
    10
    I have seen more often lately this gear developed cracks, in 2 of 4 my recent repairs. One gear even had two separate simultaneously developed cracks. I strongly recommend to clamp this gear preventively if you open up your CD changer for service.
    IMG_3393.JPG
     
    Last edited: Dec 6, 2018

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