1030 Pwer Amp adjustments

Discussion in 'Marantz Audio' started by Keith Baran, Oct 15, 2017.

  1. Keith Baran

    Keith Baran Member

    Messages:
    75
    Location:
    Nashville
    Hello all, especially any Marantz guru's
    I just finished re-capping a 1030 that I bought with one channel out. This is my first attempt at refurbishing an amp. It now turns on and sounds fantastic out of both channels.
    I wanted to perform the settings described in the service menu, the first to set the bias on the amp board.
    The service manual states I should have 7.5mv across R747 & 748. I only have .8mv across R748 and 51.7mv across R747. I haven't adjusted anything because something tells me there are problems.
    Any input would be appreciated.
    Keith
     

     

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  2. catrafter

    catrafter Marantz Specialist Subscriber

    Messages:
    6,063
    Location:
    Montana
    Hmm, I would try to adjust it to spec before deciding there is a big problem.
    Be sure to use micro clips on your meter and always have the power off when connecting and disconnecting.

    Power off.
    Volume control all the way down (CCW)
    Connect your meter, set to read DC milliVolts to J713 and J717.
    Power on
    Wait a minute or two for the reading to stabilize
    Set R723 for 15mVDC (polarity is NOT important).
    Power off.
    Connect your meter, set to read DC milliVolts to J714 and J718.
    Power on
    Wait a minute or two for the reading to stabilize
    Set R724 for 15mVDC (polarity is NOT important).
    Power off.

    The reason we are setting for 15mV instead of 7.5mV is that we are measuring across both emitter resistor in each channel instead of just one. Ohm's Law dictates twice the voltage across twice the resistance for the same idle current.
    Let us know how it goes.

    Tom
     
  3. Keith Baran

    Keith Baran Member

    Messages:
    75
    Location:
    Nashville
    Hi Tom
    Thanks for the test point info, way easier than getting micro grabbers on the resistor legs, but after 2.5 min of warm up across J713/J717 I'm getting 133.0 mv and is still rising. Across J714/J718 3.0 mv and rising. any ideas why? I'm a service engineer, working with hydraulics and lasers. I can mask a problem by over adjusting the laser, but nothing works the way it should. Do you think I should try adjusting the 133.0 mv down to 15mv or should I be checking other things? I am very ignorant when it comes to these amps, early stages of learning.
    Thanks again
    Keith
     
  4. catrafter

    catrafter Marantz Specialist Subscriber

    Messages:
    6,063
    Location:
    Montana
    Is the reading adjustable? Does it stabilize at a reasonable level? If not, then there may be a problem which we can most likely figure out.
    I like to adjust the 'bias' after a minute or two and again after several minutes, then again after a few hours. It takes time for everything to settle at the same temperature.
    If the 'bias' won't adjust or just keeps climbing, there is a problem.

    Generally speaking, as a transistor's temperature increases, it's forward current gain also increases. This causes more current to flow and the transistor gets even warmer. If nothing is done to regulate this, then you have what is called thermal runaway and parts fail due to too high of temperature or too much current flow. The 'bias' compensation sensor, (H005, H006 in this case) mounted on the heat sink, is supposed to counteract this by reducing the current as the unit warms up.

    In a perfect world, one could set the 'bias' and it would remain at that reading over any reasonable temperature. Unfortunately, in most gear, the bias thermal tracking is not perfect.
    The best that you can hope for is that the unit doesn't fail due to thermal runaway and that the bias current doesn't drop to zero when the unit gets hot after playing music at a reasonable level for several hours.

    Tom
     
  5. Keith Baran

    Keith Baran Member

    Messages:
    75
    Location:
    Nashville
    Meter across J713 & J717
    133.0 mvdc
    If I adjust R723 CCW voltage increases
    I adjust pot CW until pot is maxed, voltage only drops to 106.0mvdc( turned unit off and wipe pot to max in both directions) turn unit on, same results
    20 min up to 114.0 - 45 min 116.3 - 1.5 hr 118.0 - 2hr 120.3
    I switched positions
    Meter across J714 &J718
    3.0mvdc, I adjust R724 CW to 15.0mvdc
    20 min 17.0 mvdc, adjust back to 15.0mvdc
    1.5hr. stable at 14.9mvdc
    Why does R723 voltage increase when I turn it CCW and R724 voltage decreases if I turn it CCW?
     
    Last edited: Oct 15, 2017
  6. catrafter

    catrafter Marantz Specialist Subscriber

    Messages:
    6,063
    Location:
    Montana
    CRAP! I made a mistake about the pot numbers.
    R723 and R724 are for clipping symmetry, not bias, although they interact quite a bit with the bias adjustments.
    Power off.
    Set R723 for about mid range. Set R724 for about mid range.
    Volume control all the way down (CCW)
    Connect your meter, set to read DC milliVolts to J713 and J717.
    Power on
    Wait a minute or two for the reading to stabilize
    Set R729 for 15mVDC (polarity is NOT important).
    Power off.
    Connect your meter, set to read DC milliVolts to J714 and J718.
    Power on
    Wait a minute or two for the reading to stabilize
    Set R730 for 15mVDC (polarity is NOT important).
    Power off.

    If you can't get the bias to set properly with R729, try adjusting R723 slightly.
    If you can't get the bias to set properly with R730, try adjusting R724 slightly.

    Sorry!

    Tom
     
    Last edited: Oct 16, 2017

     

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  7. Keith Baran

    Keith Baran Member

    Messages:
    75
    Location:
    Nashville
    LOL!! If I would have been paying attention I would have noticed that. I looked over that procedure and debated just doing the adjustments before I posted "Help". I did put a mark on those pots before I tweaked them so they are very close to where they were before I started. Good news it adjusted but the pots still work in reverse R729 works CW increases, CCW decreases, but R730 CW decreases, CCW increases? weird. What do you think about this.. those pots are EXTREMELY sensitive, just a little pressure from the tweaker causes the voltage to change. It was like a crap shoot, a little touch and oh too much, a hair back and drop from 20mv to 3mv. I finally got the to 15mv. Is there a tolerance ? I set it at 15.0 and it fluctuates 15.1,15.2,15.0,14.9 and back. Do you think I should replace those pots?
    Next Question I would like to adjust the clipping, I have a scope but only a cheap digital wave generator. I thought I read somewhere that a digital generator is not acceptable. If not is there an alternative way to get a sine wave into the amp to make the adjustments.
    Hey, thanks very much for your assistance. I hate being so ignorant about these, all my posts are always"Help" hopefully soon I can offer assistance.
     
  8. catrafter

    catrafter Marantz Specialist Subscriber

    Messages:
    6,063
    Location:
    Montana
    You can clean the pots with Caig Faderlube, power off, of course. That may make them work a bit more smoothly.
    Anything that will generate a sine wave, 1KHz or so is fine for the clipping test. Just use 8 Ohm dummy loads instead of speakers. The 'clipping' point is just as the amp begins to slightly limit the peaks of the sine wave as viewed with a scope across the dummy load. You have to watch the top and bottom of the wave on the scope and adjust the volume up and down to see if you have the clipping adjust set just right.

    The board is a mirror image, left and right, so that is why the pots on one side turn opposite of the other.

    There is no tolerance that I know of.
    Good job!
    Tom
     
  9. Keith Baran

    Keith Baran Member

    Messages:
    75
    Location:
    Nashville
    I've had the meter across J713 & J717, amp on, pot set to 15.1mv. It has been on for 2 hours. I just checked it and it has drifted down to 13.5mv. Should this be a concern? I will leave it run and keep checking
     
  10. catrafter

    catrafter Marantz Specialist Subscriber

    Messages:
    6,063
    Location:
    Montana
    15mV to 13mV drift is better than fine. I think you should put the lid on it and listen to some music.
    Good job!

    Tom
     
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  11. Keith Baran

    Keith Baran Member

    Messages:
    75
    Location:
    Nashville
    Hi Tom,
    All adjustments complete, sounds great, thanks for all your valuable help. Here's a couple of pics, Rock'n The Eagles " In the city" My two year old grandson gave me a hand LOL. I The cover was nasty so I painted it white. On to a 1060 on the bench!!
    1 last question: do think it's safe to run main and remote speakers simultaneously if both sets are 8ohm? The manual says it can handle a 4 ohm load

    Marantz complete 2.jpg Marantz complete 3.jpg Boss Marantz 2.jpg
     
    Last edited: Oct 21, 2017

     

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  12. catrafter

    catrafter Marantz Specialist Subscriber

    Messages:
    6,063
    Location:
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    :thumbsup:
    It will be fine at any reasonable volume level.
    The 1060 is one of my favorite amps! As I'm sure you have learned with these low powered amps you need efficient speakers if you want it loud.

    Tom
     
  13. Richs_Trains

    Richs_Trains AK Subscriber Subscriber

    Messages:
    729
    Location:
    Tucson, AZ
    Welcome to AK Keith, your work (and your grandson's) looks great and a nice amp to listen to. Don't know if I can wrap my head around the white cover though :), looks pretty different!
     
  14. Keith Baran

    Keith Baran Member

    Messages:
    75
    Location:
    Nashville
    Hello all,I replied this post on one of my other post but I meant it to be here so....
    Question, The amp in this thread, a Marantz 1030. I finished re-capping it on Oct 19th, 2017. I checked for hum or noise at that time. 8ohm speakers attached, nothing playing, full volume and only a very faint hiss if your ear was against the speaker. This amp has seen use everyday since then, anywhere from 1 to 12 hours a day, low to moderate volumes since with no problems. Today I bent down to pick something up in front of the left speaker and there is a quiet but noticeable hiss in that speaker only, volume about 9 o'clock, it gets louder with the volume knob, then when I hit 1 o'clock on the volume knob it gets exponentially louder until 3 o'clock, there it drops back a bit, then at full volume it disappears completely . Right channel is silent regardless of pot position and balance has no affect, if I balance completely to the right, still hiss in left. Also different input selections change the behavior a bit but really the same issue.
    Any ideas?
    Regards
    Keith
     
  15. tonebells

    tonebells AK Subscriber Subscriber

    Messages:
    879
    Location:
    Florida
    Could be the 2SC458 transistors on the tone board. They get noisy. KSC1845 are the popular subs.

    Tony
     
  16. Keith Baran

    Keith Baran Member

    Messages:
    75
    Location:
    Nashville
    Now that I keep listening to it,it's really not a hiss, it's that "air" sound like when the volume is really cranked up but there is no signal, nothing playing, weird. I'm still trying to find time to replace output tyrannies I blew on a 1060 a few weeks ago during amp adjustments. Wish I had more knowledge about these things I hate "shotgunning problems by throwing in parts in. Although I have read alot about those transistors being noisy
     

     

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  17. mbz

    mbz AK Subscriber Subscriber

    Messages:
    1,817
    Location:
    Melbourne, Victoria
    Noise increasing with volume generally means the problem is at/before the volume control.
    That being the switches, input selector, loudness, mono, tape monitor, more cleaning required.

    You should verify same problem for different inputs, also try the mono and louness switches.
    If you have another pre then you could use the 1030 as a power amp (jumpers at rear) to confirm
    no noise
     

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