EQ35 end of my rope...please help

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  • DireMcCain
    New Member
    • Jan 2012
    • 5
    #1

    EQ35 end of my rope...please help

    Well, I have tried everything I can imagine...the Onkyo EQ35 is connected between receiver preouts and and Onkyo amp...without eq function, the audio passes through as it should. But when eq is activated, the amp meters peg and the amp shuts down...

    I have replaced all three ICs (Q201, 2 and 3) on the main board. I have replaced all the big caps on the main board. I have replaced the op amp (Q228) on the main board and I have replaced the two main op amps (Q1, Q14)on the eq board...I have replaced several transistors that were suspect. I have checked all the voltages on the main board and they are in spec. I have checked the voltages on the eq board and there is power.

    When I removed the two main op amps on the eq board, the amp would click on as it should...there was noise on one channel as indicated by the amp meter.

    Something somewhere is shorting out...and I'll be damned if I know where else to look...I took the eq to a local electronics shop...no help there... I would appreciate someone taking a look at the schematic...I implore you to render assistance...my mental ship is sinking...

    Thanks
    Attached Files
    Last edited by DireMcCain; 06-28-2015, 09:27 AM.
    Tags: None
    • stj
      Great Sage 齊天大聖
      • Dec 2009
      • 30997
      • Albion
      #2
      Re: EQ35 end of my rope...please help

      can you try it only connecting one channel to see if it's only left or only right that is bad.

        Comment

        • R_J
          Badcaps Legend
          • Jun 2012
          • 9535
          • Canada
          #3
          Re: EQ35 end of my rope...please help

          Have you checked to see if there is any DC voltage on the eq outputs? also check the + & - 14 volts to make sure they are correct.

            Comment

            • budm
              Badcaps Legend
              • Feb 2010
              • 40746
              • USA
              #4
              Re: EQ35 end of my rope...please help

              So both meters of the power amplifiers peg? Did you hear loud screeching sound also?
              It sounds like the EQ may be oscillating at very high frequency, try setting all the EQ to cut and see what happen.
              All the boards mounting screws are tight to get good ground?
              Never stop learning
              Basic LCD TV and Monitor troubleshooting guides.
              http://www.badcaps.net/forum/showthr...956#post305956

              Voltage Regulator (LDO) testing:
              http://www.badcaps.net/forum/showthr...999#post300999

              Inverter testing using old CFL:
              http://www.badcaps.net/forum/showthr...er+testing+cfl

              Tear down pictures : Hit the ">" Show Albums and stories" on the left side
              http://s807.photobucket.com/user/budm/library/

              TV Factory reset codes listing:
              http://www.badcaps.net/forum/showthread.php?t=24809

                Comment

                • redwire
                  Badcaps Legend
                  • Dec 2010
                  • 3906
                  • Canada
                  #5
                  Re: EQ35 end of my rope...please help

                  I suggest not running the EQ in the pre-out/amp-in until you get it fixed. The manual shows the EQ connected in the Tape-2 loop; that way you have volume control...

                  The EQ does have a built-in sweep oscillator, from 32Hz to 16kHz.
                  Maybe check it's not running and stuck injecting tones, with the sweep and spot buttons. I would suspect dirty switches first.

                    Comment

                    • kaboom
                      "Oh, Grouchy!"
                      • Jan 2011
                      • 2507
                      • USA
                      #6
                      Re: EQ35 end of my rope...please help

                      Originally posted by redwire
                      I suggest not running the EQ in the pre-out/amp-in until you get it fixed. The manual shows the EQ connected in the Tape-2 loop; that way you have volume control...

                      The EQ does have a built-in sweep oscillator, from 32Hz to 16kHz.
                      Maybe check it's not running and stuck injecting tones, with the sweep and spot buttons. I would suspect dirty switches first.
                      If they're those "rail" switches that were often ganged together, grounds were sometimes carried by the rails. Strain from pushing the switches can break the solder here, opening the grounds and causing strange things to happen.

                      You need the +/- supplies to all opamps before you can otherwise troubleshoot it.
                      "pokemon go... to hell!"

                      EOL it...
                      Originally posted by shango066
                      All style and no substance.
                      Originally posted by smashstuff30
                      guilty,guilty,guilty,guilty!
                      guilty of being cheap-made!

                        Comment

                        • DireMcCain
                          New Member
                          • Jan 2012
                          • 5
                          #7
                          Re: EQ35 end of my rope...please help

                          Thanks to everyone for the help...I am working to pursue all your suggestions...
                          yes, both channels spike...interesting is that when Q1 and Q14 are pulled there is noise on the left channel...but not the right...and no spike...

                          I'll be back...damned if I am going to give up...there has to be an answer.

                            Comment

                            • redwire
                              Badcaps Legend
                              • Dec 2010
                              • 3906
                              • Canada
                              #8
                              Re: EQ35 end of my rope...please help

                              Because the EQ gyrators are part of one big loop, with the results of each band summed together, it is a bit hard to troubleshoot.
                              One bad op-amp/capacitor/slider on any EQ band can upset the whole circuit. Onkyo mixed some dual op-amps between EQ bands and channels i.e. op-amp Q4 is 16hz L and 64Hz R which adds to the fun.

                              Q1, Q14 are dual op-amps for the EQ main output buffer and the EQ summation amp. The only thing between these op-amp outputs and the RCA jacks I see are switches.

                              Can you describe the "noise" - is it white noise, crackling, rumbling, squealing, farting, chirping? Does it change if you tap gently (with a plastic pen) on the PCB's?

                              As a start, I would measure +/-14VDC power and then write down the DC voltages on the output pins (1,7) of all op-amps. Just looking for one that is not close to 0V. I know it's a hassle but this beast has >14 op-amp ICs...

                                Comment

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