Marantz 2270 works for 5 mins then click off

Discussion in 'Marantz Audio' started by Marc1234, Jun 9, 2018.

  1. willyrover

    willyrover Super Member

    Messages:
    3,033
    Location:
    Hamilton

    The green box is the bridge rectifier H005.

    The red wire is your DC output. Set your meter to DC and measure between white and red wires.

    The 95-103VAC between J804 and J805 is concerning. What readings do you get with meter set to AC between J804 and chassis, and J805 and chassis?

    I'll try to open up my 2270 today and take some readings for comparison.
     

     

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  2. willyrover

    willyrover Super Member

    Messages:
    3,033
    Location:
    Hamilton
    deleted
     
    Last edited: Jun 10, 2018
  3. willyrover

    willyrover Super Member

    Messages:
    3,033
    Location:
    Hamilton
    Ok, so I took some measurements in my 2270. Many are rounded to the nearest volt.

    Please make sure that the wire link to chassis circled in red is intact. This is the ground reference for the board and if it's missing, voltages will do evil things.

    When taking point to CHASSIS measurements, make sure your black meter lead is attached to a point on the metal chassis, such as the spot in green box.

    1. At the bridge rectifier (the green box):
    ...between ORANGE and ORANGE - meter set to AC: 69VAC
    ...between WHITE and RED - meter set to DC: 94VDC

    2. At the main filter caps (large can capacitors):
    ...between the two lugs on each cap - meter set to DC: 47VDC
    (one will be negative and one will be positive depending on how your meter leads are oriented)

    Please recheck the above measurements on your unit with correct meter settings.



    3. At the power supply board:
    ...between J804 and J805 - meter set to AC: 70VAC
    ...between J804 and CHASSIS - meter set to AC: 35VAC
    ...between J805 and CHASSIS - meter set to AC: 35VAC

    ...between J807 and CHASSIS - meter set to DC: 45.7VDC
    ...between J806 and CHASSIS - meter set to DC: 31.6VDC
    ...between J801 and CHASSIS - meter set to DC: 12.7VDC
    ...between J802 and CHASSIS - meter set to DC: 34.94VDC (regulated 35V supply- adjustable)

    These voltages are all ROCK SOLID. There is no drifting whatsoever.



    IMG_0839.jpg
     
    Last edited: Jun 10, 2018
  4. Marc1234

    Marc1234 New Member

    Messages:
    27
    Ok so after taking sregor’s advice I went out this morning and got some new 9v batteries for my dvm and low and behold I have new Vdc readings to report.! Never would have thought it could be a battery in my meter so note to self and others change those batteries in digital meters.! Will also change the one in my work dvm when I get back from vacation in a few weeks so new readings are as follows
    J-801 13.9vdc
    J-802 35vdc
    J-807 47vdc
    J-804 40vac
    J-805 36vac
    J-804 to j-805 72vac
    I still get no relay click it was working as stated above for a few minutes then would click off now it will not click on at all the only thing I have change besides the caps on boards listed above has been the mje243g devices on the p-750 boards these 2 devices were changed after the recap
     
    Last edited: Jun 10, 2018
  5. willyrover

    willyrover Super Member

    Messages:
    3,033
    Location:
    Hamilton
    Those voltages look better. The battery thing surprised me too. The LCD on my meter dims out before readings go off.

    1. You mention replacing MJE243G devices. Did you verify the pinout of the old vs new devices and ensure they were installed correctly?

    2. So I guess we need to determine if the relay isn't engaging because the protection circuit IS WORKING properly or because there is a fault in the relay circuit.

    Check for VDC between CHASSIS and J813 for left channel/J814 for right channel on power supply board. This is the input from the power amp to the protect circuit/relay. The meter reading is DC offset and should be a few mV at most.

    Readings from my unit are:

    J813: 6 mVDC
    J814: 9 mVDC


    If higher DC is present but still reasonably low, like less than 1.5VDC, see if you can bring it down with R762 (offset adjustment) on power amp board for applicable channel.
     
    Last edited: Jun 10, 2018
  6. Marc1234

    Marc1234 New Member

    Messages:
    27
    Ok so from chassis to j-813 and j-814 which I’m assuming are where the blue and yellow wires connect to the relay itself On the p-800 get .03 to .05vdc on the blue wire on the yellow wire I read open.?
     

     

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  7. willyrover

    willyrover Super Member

    Messages:
    3,033
    Location:
    Hamilton
    Blue wire J813 is 30-50mV...not enough to trigger protect circuit so Left channel looks ok.

    Yellow wire J814: 'Open' doesn’t make sense for a voltage reading. It’s probably reading 'overload'. Try setting your meter to a higher range (20v or 200v) and measure again. I bet you have significant voltage on the yellow wire. If you do, desolder the yellow wire from J814 and test the amp to see if it comes out of protection.
     
  8. Marc1234

    Marc1234 New Member

    Messages:
    27
    Indeed amp comes out of protection with yellow wire removed from j-814 let it sit for half an hour on and stayed on with only blue wire connected at j-813 so I have a problem in the right p-750 could you possibly point me as to where to look the schematic for these units is horrible ..! Also thanks for the outstanding help and knowledge I might just start doing this on the side it’s very interesting and refreshing at the same time
     
  9. Steven Tate

    Steven Tate AK Subscriber Subscriber

    Messages:
    2,617
    Location:
    N. Richland Hills, TX
    You could try reconnecting the yellow wire, removing the outputs from that side and see if it goes into protection. Bad outputs are a common cause of a unit going into protection. If you do, be sure and take a photo to ensure you get them back in the same way.
     
  10. Marc1234

    Marc1234 New Member

    Messages:
    27
    Resolidered yellow back on with main outputs removed amp came out of protection then after 3 or minutes went back into protection mode could hear relay click 3 or 4 times then I killed the power
     
  11. willyrover

    willyrover Super Member

    Messages:
    3,033
    Location:
    Hamilton
    Yes, so we need to focus on the right side amp module P-750.

    Did you manage to get a DC voltage reading from the yellow wire using different meter settings before removing the outputs? (see post #27)



    Also, while the outputs are removed from the right channel, check them for shorts using your multimeter.

     

     

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  12. willyrover

    willyrover Super Member

    Messages:
    3,033
    Location:
    Hamilton
    Since the unit worked for a while with the outputs removed, then clicked off, there is still an issue on P-750.

    Service manual suggests checking R762 (2.2K trimmer for DC offset. Make sure it's working properly.)

    Also, check H762 and H763 zener diodes.

    Screen Shot 2018-06-10 at 6.58.29 PM.png
    Screen Shot 2018-06-10 at 7.09.38 PM.png
     
    Last edited: Jun 10, 2018
  13. Marc1234

    Marc1234 New Member

    Messages:
    27
    So I pulled the output transistors and both tested ok so I got the voltage off the yellow wire j-813 with main outputs in and out with the same result of -46vdc maybe the voltage here will help sorry I didn’t grab it the first time. I will try and get these diodes out of circuit to test tonight will update once done
     
    Last edited: Jun 10, 2018
  14. willyrover

    willyrover Super Member

    Messages:
    3,033
    Location:
    Hamilton
    Getting closer. Just have to figure out why you’re getting full negative rail voltage on the output.

    Let’s see how those diodes test.
     
  15. Marc1234

    Marc1234 New Member

    Messages:
    27
    H-762 as well as h-763 have good push can I test r-762 and r-763 the 2 vr resistors In circuit or should I pull a leg unless these results of good diodes point to another possible fault point
     
  16. willyrover

    willyrover Super Member

    Messages:
    3,033
    Location:
    Hamilton
    I would pull one leg of the diodes to check them. I would do a quick check R762 in circuit but it's not likely the problem since you're getting full negative rail voltage on the output. No need to check R763 at this point.

    Assuming you had your meter leads connected with the correct polarity when you measured -47VDC on the output, we need to figure out why that -47VDC at J761 is showing up at J757 (the output of the amp module).

    Let's check zeners H764 and H765 next as well as emitter resistors R788 and R789.

    If those check out, it's time to start pulling and testing H767, H757, H755, H759 and testing for shorts - again, assuming the DC at the output is in fact negative. I usually test for shorts in circuit, and if a short is measured or I get weird readings, pull the device and check it again.

    Screen Shot 2018-06-10 at 10.55.34 PM.png
     

     

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  17. Marc1234

    Marc1234 New Member

    Messages:
    27
    Yes I pulled legs of h-762 and h-763 when testing both show good push. Dc voltage measurement was taken twice with and without output transistors from j-803 rear chassis grounding lug for p-800 -47vdc was observed in both instances I will pull h-764 and h-765 as well as r-788 and r-789 tomorrow if possible and report findings. Thanks again for your outstanding guidance
     
  18. Marc1234

    Marc1234 New Member

    Messages:
    27
    Update I pulled all devices on right p-750 found NO faults resolidered and reassembled amp now shows 00.2vdc on yellow wire or j-813 so I’m assuming it’s good to resolider to j-813 and fully test.! Did partial test left amp on for 30 minuets with only j-814 blue wire connected at relay and with dvm black lead on j-803 the p-800 chassis grounding lug and with red lead on yellow wire coming from right p-750 at j-757 monitored for 30 minuets with a solid steady feed of 00.2vdc Will update after full test..!!! So any ideas as to where I might have been getting that voltage from I would like to remedy the issue so it doesn’t randomly show back up maybe a cracked shielding on a wire that was touching chassis.?bad or cold solder point.! Or maybe I just did something after the first rebuild when reinstalling.?
     
  19. willyrover

    willyrover Super Member

    Messages:
    3,033
    Location:
    Hamilton
    00.2vdc is an odd reading. If that's 200mV, it's still fairly high, though probably not enough to trigger the protection circuit and it could probably be dialed down. If you meant 0.02VDC (20mV) then that's way better, or 0.002VDC (2mV) is excellent.

    In any case, you might as well reconnect the right channel to the relay and see what happens. If the DC on the yellow wire is gone, you either corrected a bad solder joint or solder bridge by removing or reinstalling the parts, or moving the board around, or I guess heat from soldering might have revived a dead part.

    If the unit comes out of protection with both amp modules connected, perform the audio adjustments #1-4 ASAP.

    Screen Shot 2018-06-11 at 7.40.49 PM.png
     
  20. Marc1234

    Marc1234 New Member

    Messages:
    27
    Scratch that after returning and and restarted amp after it had sat for an hour or so I have the same -46vdc WTH and yes that was supposed to read 0.02vdc steady :(
     

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