Marantz 1030: Extreme Bias Voltage and Distortion on Left Channel

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • TechGeek
    Computer Geek
    • Jan 2015
    • 2254
    • USA
    #1

    Marantz 1030: Extreme Bias Voltage and Distortion on Left Channel

    Hey all. I have this Marantz model 1030 amplifier with some problems.

    Problem 1: Left channel has extreme distortion under any kind of load. If you crank the bass control, it distorts to hell and gone.

    Problem 2: When attempting to set the bias voltage for the left channel, it's ENTIRELY too high. The service manual states 7.5mVDC at idle. It won't go below 130mV. The right channel has no distortion and I was able to successfully set it's bias current to 7.5mV.

    I think what's going on here is that something is pulling the bias voltage way up on the left channel and when you load that channel down, the high bias voltage causes the transistor to be driven into distortion.

    What might be pulling the bias voltage up? Will this kill the transistors in short order?

    TIA.

    Service Manual: https://cdn.badcaps-static.com/pdfs/...739e9f0da8.pdf
    Don't buy those $10 PSU "specials". They fail, and they have taken whole computers with them.

    My computer doubles as a space heater.

    Permanently Retired Systems:
    RIP Advantech UNO-3072LA (2008-2021) - Decommissioned and taken out of service permanently due to lack of software support for it. Not very likely to ever be recommissioned again.
    Asus Q550LF (Old main laptop, 2014-2022) - Decommissioned and stripped due to a myriad of problems, the main battery bloating being the final nail in the coffin.


    Kooky and Kool Systems
    - 1996 Power Macintosh 7200/120 + PC Compatibility Card - Under Restoration
    - 1993 Gateway 2000 80486DX/50 - Fully Operational/WIP
    - 2004 Athlon 64 Retro Gaming System - Indefinitely Parked
    - Main Workstation - Fully operational!

    sigpic
    Tags: None
    • andy1
      New Member
      • Apr 2019
      • 9
      • USA
      #2
      Re: Marantz 1030: Extreme Bias Voltage and Distortion on Left Channel

      I would disconnect the speakers (to be safe) and turn down the volume control and start comparing voltages with the working channel. There are just a handful of components to check and it should be quite easy to do that. Pay attention to the transistors H 501-506 and the nearby parts. Also, if you can lift those transistors and check them individually, you should be able to narrow down easily.

        Comment

        • petehall347
          Badcaps Legend
          • Jan 2015
          • 4426
          • United Kingdom
          #3
          Re: Marantz 1030: Extreme Bias Voltage and Distortion on Left Channel

          test emitter resistors values ...
          are the outputs running very hot ?

            Comment

            • redwire
              Badcaps Legend
              • Dec 2010
              • 3907
              • Canada
              #4
              Re: Marantz 1030: Extreme Bias Voltage and Distortion on Left Channel

              I think it's a quasi-complementary output stage, so the bias works differently.

              To check the transistors I would compare readings between channels (power off, with multimeter on diode test) of the output transistor and driver VBE junctions. Also the bias diode array, if they are high Vf then bias would be high. I think SV-03A brown boat can be replaced by three Vishay 1N4150's in series, for 2.18V at 1mA. More info on them here:
              https://audiokarma.org/forums/index....acement.756284

              Rarely, high bias and distortion is from oscillations, if the electrolytics are low value.

                Comment

                Previous template Next

                Related Topics

                Collapse
                • sima112
                  Marantz pm 6005 right channel not worknig
                  by sima112
                  Hi guys,
                  I need a help with my Marantz pm6005. It started to have weaker the right channel a few months ago, than it got back to normal and now it has lost sound completely on the right channel. At the final stage it was loosing the channel for a while and than it returned. After it has disappeared completely I could forced it back by unplugging the source form CD (which I normally use) to phone and back. It would then work for a few minutes and died again. Now it is possible power up and all function works normally (apart the right channel ) on all inputs, except the phone both channel...
                  01-30-2023, 12:11 PM
                • eccerr0r
                  old X58 triple channel board... memtest86 memory speed?
                  by eccerr0r
                  Anyone run memory speed tests with an old X58-based triple channel 1st gen or any other >2 channel board? The one I have is a Gigabyte I think.

                  Anyway I had four 4GB DDR3-1333 modules in the 6 memory slots and got around 11GB/sec memory speeds assuming that it went dual channel since it didn't have enough modules for triple channel. Now I stuck in two more 4GB modules, but they are DDR3-1600. I'm still getting 11GB/sec speeds according to memtest86...

                  Just wondering, anyone do memory speed analysis on these triple (and higher) channel memory boards? Are there any...
                  06-28-2025, 09:06 AM
                • acedogblast
                  [Marantz SR5012] Center channel keeps going into ASO/Overcurrent protection.
                  by acedogblast
                  First off I would like to thank this community as it has provided me with great information that has helped me greatly on my repair for this Marantz SR5012 AV receiver. I am creating this new thread as the other 2 that I have created here has had their original question/problem solved and I plan that this is the final thread on my repair. Please note that this is my first time repairing audio amplifiers so I may not be aware of common issues and things to know.

                  Lets start at what I have done so far. Random speaker popping on all channels is fixed by replacing the 2 large filter...
                  03-01-2023, 08:24 PM
                • AudioGuy88
                  How to bias a Plinius Odeon 6 channel amplifier
                  by AudioGuy88
                  Hi everyone,

                  I am working on a Plinius Odeon 6 channel amplifier. Not much wrong with it, but I replaced some caps (20 years old) and decided to check the bias current.

                  The manual says

                  1.
                  Code:
                  [1] Check the right DC servo is set within its operating window.
Use VR2 to set TP5 to within –3.0 to +3.0 volts.

[2] Check the bias current is correct once the amplifier has warmed up, typically 15 minutes.
Use VR1 to adjust the rail current to 140mA or 52.5mV across any emitter resistor (35mA per
device).
                  I am assuming...
                  01-28-2023, 09:30 PM
                • spleenharvester
                  Reverse engineering of 18650 4-channel tester
                  by spleenharvester
                  Hi friends

                  I have reverse engineered this tester, schematic is attached and is complete except for capacitor values. These testers annoyingly have no model number but they are the ones you find on the first page of just about any website if you type in "18650 4-channel tester". There is also a 2-channel variant and a newer 8-channel variant. They are very cheap (about £15) and can measure voltage, current, internal resistance and capacity. They have a multicolour display for all these statistics. They also have terminal blocks so that if you want to use a breakout board...
                  05-04-2025, 02:43 AM
                • Loading...
                • No more items.
                Working...