1. Time for some upgrades in server hardware and software to enhance security and take AK to the next level. Please contribute what you can to sales@audiokarma.org at PayPal.com - Thanks from the AK Team
    Dismiss Notice

Kenwood KR-V9020 Display question

Discussion in 'General Audio Discussion' started by ranukic, May 13, 2018.

  1. ranukic

    ranukic AK Subscriber Subscriber

    Messages:
    190
    Location:
    Fox Valley, WI
    Hey,

    I picked this up for my garage and I noticed the display flashes from bright to dim. Has anyone run across this type of issue before?

    Thanks,

    James
     

     

    Please register to disable this ad.

  2. restorer-john

    restorer-john Addicted Member

    Messages:
    6,521
    Location:
    Australia
    The VFD drive circuitry and the VFD connection to its PCB will need investigation.

    Can you elaborate? Is it a regular flashing or stimulated by shock to the cabinet or is it intermittent. Is the 'bright' brighter than normal or is the 'dim' darker than normal? Does it settle down or constantly flash?
     
  3. ranukic

    ranukic AK Subscriber Subscriber

    Messages:
    190
    Location:
    Fox Valley, WI
    Thanks for responding restorer-john. I uploaded a video of it that can be seen here I thought it would make for a better explanation of the flickering. I currently am driving (4) 6 ohm outdoor 120 watt Yamaha NS-AW150 speakers and a passive sub. And I normally have the music at 3-4 so not extremely loud.

    Thanks,
    James
     
  4. restorer-john

    restorer-john Addicted Member

    Messages:
    6,521
    Location:
    Australia
    Hi James,

    What electronics skill level do you have?

    The issue is likely to be in the switching or power supply to the high voltage (-28v) to the VFD (FL display) as the entire display is fluctuating, but appears otherwise fully lit and functional. The heaters are fine.

    I would start in the power supply for the VFD, including checking the FL (VFD) switching and the zener regulator as per the two schematic captures I have taken below. These are from the model 8020, but I am hoping the general parts placement is similar to yours.

    Check the voltage on D24/C11 and ensure the cap and the zener are good.

    vfd 01.JPG

    vfd 02.JPG


    On the power supply, check C163, the 47uF 63v cap- in fact, I'd just replace it as it could cause this entire problem. Check Q23 or equivalent is being switched on or off and doesn't have a fluctuating base drive to it. Check the -30v is stable on not full of ripple. (use a DMM on ACV/mV to see that or a DSO/CRO)

    Assuming the main boards are the same on this model (I'm hoping) this is where c163 lives:

    c163.JPG
     
    Last edited: May 14, 2018
    John Daly likes this.
  5. ranukic

    ranukic AK Subscriber Subscriber

    Messages:
    190
    Location:
    Fox Valley, WI
    Thanks Again, I will be traveling for the next few days so I won’t get back to this for a while. I had planned on changing the caps but I will also take a look at the diodes to see if there are any burned marks on the boards. From what I have seen in the past if the diode goes it causes a short and blows the fuse. Atleast for the PS that is.

    I will keep you posted

    Thanks,
    James
     
  6. restorer-john

    restorer-john Addicted Member

    Messages:
    6,521
    Location:
    Australia
    It's not diodes. Start with the capacitor I have highlighted and post back to this thread afterwards.
     

     

    Please register to disable this ad.

  7. ranukic

    ranukic AK Subscriber Subscriber

    Messages:
    190
    Location:
    Fox Valley, WI
    AE5361C8-C0A2-4D24-A0B3-0157B6271F1C.jpeg BE1F2622-C473-4F83-BCB6-8C4DBC8E9F58.jpeg E03A7A41-6D11-40A0-A48B-18C616B6F611.jpeg Hey,

    So I took the cover off and peaked inside. I will need to replace several caps on the PS board. Took some photos for you to see how she was mistreated over the years.

    I will let you know how it turns out.
     
  8. ranukic

    ranukic AK Subscriber Subscriber

    Messages:
    190
    Location:
    Fox Valley, WI
    That fixed it. Thanks!
     

    Attached Files:

  9. restorer-john

    restorer-john Addicted Member

    Messages:
    6,521
    Location:
    Australia
    Sweet. Glad you got it going. :)

    I hope you cleaned out all that dust and dirt too...
     
  10. ranukic

    ranukic AK Subscriber Subscriber

    Messages:
    190
    Location:
    Fox Valley, WI
    Oh yes I did. I took some compressed air to it then used some deoxit and a couple different types of brushes to clean up the boards. Thank you again
     
    restorer-john likes this.

Share This Page