Help fixing Problem with Kenwood KRF-X7775D

Discussion in 'General Electronics Chat' started by Harveyba, Feb 8, 2014.

  1. Harveyba

    Thread Starter New Member

    Feb 6, 2014
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    I have a Audio Video Sourround Receiver that stop sending Sound to the Output of the Speakers in normal operation Modes.
    When i switch it on in Test mode the analog Inputs are working but if i switch bag to normal operation mode there is no sound at all.
    I have the service Plan and the operation handbook. What i at the Moment don´t have is a the IR Remote for it because my Dog used it as a bone ;-)).

    Please help me understand where i can look or test to solve the Problem i searched the net but there was many about that Problem without even one Fix that i can use to solve it.

    Thanks from Germany out of NRW from Jürgen to all that can or will try to help me going back on line with that device.
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    So I fixed one couple of years back.

    I remember no Audio output from tht either.

    I did replace some DSP related SMD chips but to no Vail.

    It was some capacitor issue. I recall couple of smaller caps and a super cap near a μC.

    The PCB is at the bottom most. Where I'll know when I see the PCB.

    Post some pictures of the inside so I can recall my rusty memories.

    I think it was a uC not resetting issue. Well, tht's what I figured cause it still works like a charm
     
  3. Harveyba

    Thread Starter New Member

    Feb 6, 2014
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    So thank for the fast reply.. which Board should i put out to take a photo off it..
    I have attached some Photos off the hole unit in mounted all in.

    Look at he Photo´s and tell me which Unit i should make a better Picture off.

    Capacitors ESR Measurement is in my work Place so i can check Caps for it´s health.
     
  4. R!f@@

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    Apr 2, 2009
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    The uC is at bottom board. The third picture.
    You can see the AVR's mounted on the heatsink.
    The uC cannot be seen in the third picture as it hidden by the metal support.
    The capacitors I changed are around the big spider IC ( SMD ).

    One problem
    My memory is like cigarette ash. I found the guy who is using it and I found out it wasn't the audio that was the problem.

    I remember now that it had a uC issue as I recalled earlier. The input selector malfunctions. The darn thing had a mind of it's own. It keeps switching input select on it's own.
    So the caps around that uC fixed the problem.

    I still like to know how you came directly to me to this forum. Please tell me.

    Your amp as you said can hear the test tones. Right ?
    So tell me if you can vary the volume level when the tones are played.

    We might have to get down and dirty on this beast.
    You cannot imagine what I went through trying to play it while all the boards are on the bench.

    I might need some time to study the schema. I can only answer you when I am in workshop. House connection is like crap. Last night I ran out of data limit while at my house. And the connection is like worse than a phone line and they say faster better modems and ****.

    Do you have a audio tester. It will be easier to trace Audio while a signal is injected.
    Scope would work too. But ears are better for me than looking at scope every time.
    This way you can concentrate on the PCB better.
     
  5. Harveyba

    Thread Starter New Member

    Feb 6, 2014
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    I was looking around the Internet for fixing Problems with this Unit and on one Board (not this Board) where you and you told the Person there that you only can help him with your Problem here on this Board and only in a Threat and not per PM Messages.
    So i read all i can find about my Problem and then i give up... The only way to fix it i thought was searching for you and i was happy to found you on this Board .
    Like i said before it is no hurry to fix it because i have Music and Film Tone out of a other unit this time...

    So jet bag to the Unit.. I press The power button by inserting the Plug in the wallet 230V AC inlet.. Then in the Display all Dots are bright and after a small Time i hear Radio Noise out of the Speakers (only connected L/R Front) .. The Sound is loud so i must adjust it .. I can now adjust volume change to input CD1 and in Tuner mode i can store Stations .. But after switch off the Unit all off the Sound is gone no Noise at all. When i connect a Signal on the 6 Chanel input for F/R Front i can hear and adjust Music from the input signal but it is very small and not so loud as in the Test mode.
    All other input´s are dead no sound at all . (Digital input i have not tested at the Moment) but i can do that if it is for some Reason..

    Thank´s out of Germany Jürgen..
     
  6. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    To make sure abt your problem.

    Answer the questions one by one
    1. At first switch on, you can hear test tones from all speakers?
    2. Can you adjust the volume of the test tone while the test tone are being heard?
    3. You can Rx radio and hear radio, and adjust volume too?
    4. Does the amp continues to function after this as long as you do not power down.?
    5. During this time check for analogue inputs. Can you hear sound/adjust volume while in CD, tape , and all the rest analogue inputs. Inject signal to the respective inputs one by one. Reason is to check analogue switching Assy.

    After this. Tell me.

    6. Did you say the Amp refuses to produce any sound after turning off ( into stby ) and back on ?
    7. If the above case is true then how long do you have to keep the amp off ( in stby or AC cable unplugged, tell me ) to get it working again, so that it again works as per the first 5 questions.
     
    Last edited: Feb 9, 2014
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    You can Inject audio but do you have the means to trace the audio as I do.

    I use a small LM386 battery powered speaker built into a PC speaker with volume and all.
    The input is fed to the volume with a shielded cable and a meter probe attached to the other end.
    This little thing is very useful in tracing low level signals in amps and preamp.
    My ears do the rest while I probe the PCB. I can find noise and low audio and all that.

    Ofcouse you have to keep the probe from HV DC bus. If not you will blow more IC's that way. I know I did.
     
  8. Harveyba

    Thread Starter New Member

    Feb 6, 2014
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    I have a amplifier in a small pen case with a 9V block Batteries in it to find Audio signals.
    This unit has a high resistor in series of the Input and a Cap so there is no Limit to test on all pin´s except AC Lead ;-)).

    About your first Question (1). I hear a loud Noise after all Digits in the Display where light and back dim again. The Noise is like a FM Noise without Station. I think it is coming out of the Tuner. I have only attached a CD Deck in CD1 in. No Noise generator or other Things..

    (2) There is no Test tone only a FM Noise (1) and i can adjust it´s Volume to.

    (3) I can tune a Station and adjust Volume to..
    (4) This Station stays Tuned and i can hear it for a long Period.. (without Prologic) only in Testmode (Stereo)
    (5) i can change to CD and hear it (only Stereo) without Prologic Sound..
    (6) after switch off and on all is dead (only the 6 Chanel input is heard very soft by maximum Power) You can turn to all Functions and memory Sations in FM ... but no Sound !!
    (7) off and with Power pressed the Plug into the Wallet the Sound is back again only in Stereo mode.

    I will tomorrow Test optical Audio Input and Video switches..
     
  9. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    This is rather strange fault.

    Can you inspect the capacitors I told you about.

    The Pictures do not show the chip so I cannot point you to the ones yet.
     
  10. Harveyba

    Thread Starter New Member

    Feb 6, 2014
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    The C4 is not insert there is a Gold-Cap in why i don´t know
    The other shown as normal no blow up or leakage.

    So i test the rest of digital in and Video Tomorrow when i come from Work.
    I must now go to bed / you know it is other Time here ;-)).
     
  11. R!f@@

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    Apr 2, 2009
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    Looking at the last picture.

    μCom IC (IC3) This the one my one was giving me the issue.
    I changed, C4 ( memory cap I think ) and the two blue ones at it's sides.
    I remember cause I had a hard time to find a super cap during that time.

    Check them for ESR. Replace if necessary and post back.
     
  12. Harveyba

    Thread Starter New Member

    Feb 6, 2014
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    So now i am bag to the Unit... I have changed the Gold Cap... (only bevore disassembled the Unit) ..

    The Unit can now only be switched in The Test mode by Pressing Input select and Power this was before easier to go into that Mode ;-)..

    But the hole Sound in normal Mode is gone as well like before.

    Now i disassembled the Unit and take out the Card´s and looked under the Layer Board for Inspection.

    I found that the Big AC/DC Bridge is soldered out at all Pin´s could that be a Part of the Problem.. The Solder Pin´s are very cold and scratched.

    I want to ask you if it is a good Idea to take out all Cap´s for testing it´s ESR and put in new ones with better ESR ( by the Same Cap and Voltage)

    How about the AD/DA Board on the Photo with Software on a Flash is there a Way to look on it and if necessary change the Software on the Flash..

    Thank´s for Today i come bag Tomorrow and we look forward to fix this Unit.. Jürgen
     
  13. R!f@@

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    Apr 2, 2009
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    Re check the ribbon cables and re seat them properly ..be gentle

    First Do look for dry joints and resolder. You know you should know that. :D

    The caps are good, right ?
    You do not need to replace them if you check them with cap meter. If it's bad then replace them.

    Now do inspect all the caps. Before desoldering look for obvious signs.

    The Leads of the caps can be seen. So just look at the leads for oxides. Or any leakage signs at the caps leads and the PCB around every cap for leaked electrolyte.This is very first thing I do.

    You need to re seat the ribbons properly. This is very tricky thing. All sort of shitty thing happens if ribbons are not connected. Even one line of the cable will give you nighmares
     
  14. R!f@@

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    Apr 2, 2009
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    PS....Please check for typo's. You are confusing me more than your problem.
    Remember to read what you posted so it is correct in every way
     
  15. Harveyba

    Thread Starter New Member

    Feb 6, 2014
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    1
    So i have inspected the Board under the Card´s ..
    Soldered every Point that was bad new..
    Changed the CAPS near the YCom IC..
    Checked all Voltages from the Supply
    Everything looks good but no Sound like bevore..
    Bad Day i hoped that what i found was the key for the Problem.
    Now we must think about checking where the Signal is stopped.
    I check Optical Digital Input tomorrow because today i must go to a Birthday Party for some Drink´s..
    Good Weekend from Germany Jürgen
     
  16. R!f@@

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    I will need to study the diagram now....!
     
  17. marva

    New Member

    Feb 11, 2014
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    Dear Harveiba and R!f@@ i have the same problem with my Amp .
    If its important i have found this : if i switch on the B Group Speaker output i heare the sound but so smaller , Harveiba for you is the same?
    One important question , how i can get test mode ?
    Thank you.
     
  18. R!f@@

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    Apr 2, 2009
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    Did not I tell you not to hijack the thread at first.
    Tsk...Tsk..!

    Please start ur own thread.

    By the way to get into test mode.
    "Turn on the power supply while pressing the "INPUT SELECTOR DOWN" key, to make a set in test mode.

    The system is initialized and test mode is cancelled if unplug the AC power cord
     
  19. Harveyba

    Thread Starter New Member

    Feb 6, 2014
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    :D I will today test if when i connect a optical digital audio input the sound will be coming out of the set or not..

    I was the last week´s in the garden because of the fine weather in our country,
    But now it is bad outside and the set must be fixed ...:D:D:D

    Have you now found a way to make the search for the Problem easier..
     
    Mano Fernando likes this.
  20. R!f@@

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    Apr 2, 2009
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    I posted that you double check all the ribbon / flex cables for damage and check if they are seated properly
     
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