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Marantz 2270 works for 5 mins then click off

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

  1. Marc1234

    Marc1234 New Member

    Messages:
    33
    Could this be an intermittent problem with a device if so that blows. Can a device work and then just stop working intermittently.?
     

     

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  2. willyrover

    willyrover Super Member

    Messages:
    3,120
    Location:
    Hamilton
    It could be temperature related. After resoldering, the problem seemed to go away. After sitting for a while, the problem came back.

    If you have a hot air station, I could try heating the transistors on P-750 one at a time while monitoring the -47VDC.

    Without hot air station, you could use a hair dryer or a heat gun (on LOW) to warm the board and see if the fault goes away. It will be hard to focus the heat on specific components but you might be able to confirm a heat related fault.

    You can also heat individual PLASTIC CASED transistors with your soldering iron tip. I've never done this with METAL CASED transistors since the case could be in circuit. If I were to try it with metal cased transistors, I would use an insulator, like a piece of mica or a couple of SIL-Pads between my iron and the metal case.


    You could also try COOLING each device individually. A can of freeze spray or an air duster can used upside down works in a pinch.

    I might also remove the output transistors again during this testing process to eliminate them as a problem and prevent damage to them should something evil happen.
     
  3. Marc1234

    Marc1234 New Member

    Messages:
    33
    No difference I could tell cold or hot on devices so I started studying the schematic left amp is indeed wired like this on j-758 to ground right is different there is a ground from j-761 to to j-758 I included a picture this is also where main outputs -46vdc comes from could this be my problem just thinking someone before me tried to block that -46vdc with a .01uf is that what they were trying to do possibly or does that look correct to you also of note the bottom j-761 has a white wire soldiered on the post the .01uf cap is soldered on to it with black wire which I find highly suspicious
     

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    Last edited: Jun 11, 2018
  4. willyrover

    willyrover Super Member

    Messages:
    3,120
    Location:
    Hamilton
    Well that doesn't look right. Is C762 still present on P-750?

    I can see if that cap exists on my 2270 later tonight.

    See what happens when you lift a leg of that capacitor.
     
  5. Marc1234

    Marc1234 New Member

    Messages:
    33
    Yes c-762 is present and accounted for..! So I took the leg of that .01 cap off of j-761 just using the ground coming from j-758 amp turned on came out of protection quickly and I had a reading of 0.08vdc so I used r-762 and got reading down to 0.03vdc to 0.02vdc after about 3 minutes voltage started getting haywire I was seeing peaks and valleys showing -0.03 to 0.06 now I read 1. Open..! this thing has me frustrated very intermittent it seems. picture is about 2 minutes in after adj. r-762 because I thought I had it whooped NOPE..!
     

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  6. Marc1234

    Marc1234 New Member

    Messages:
    33
    Ok so just went back out and checked I have my -46vdc back and after just watching my meter for 10 minuets or so the voltage never goes over -46.4vdc but every now and again it drops to the correct 0.03 vdc then bounces to -22.xx or -30.xx then back down to 0.03 then back up to -46 and stays there for a minute or two then the same low bounce..? Could this be the intermittent device working for a second or two then failing again..?
     

     

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  7. willyrover

    willyrover Super Member

    Messages:
    3,120
    Location:
    Hamilton
    Are these results with the output transistors in or out?

    It has to be an intermittent short somewhere on P-750. And it definitely sounds heat related as the fault shows up consistently after about 3 minutes. When the fault appears, I would start hitting different areas of the board with freeze spray to see if you can't get the voltage bouncing around or back to normal.

    I would also consider going over the entire P-750 board and reflow every solder connection on it. Examine every component for broken or corroded legs - and retest.
     
    Last edited: Jun 12, 2018
  8. Marc1234

    Marc1234 New Member

    Messages:
    33
    Don’t know if this could effect these symptoms or not but the rear main 55v 9kuf cap has a relatively deep puncture in it it is not thru the outer aluminum can but as the pic shows it is about an 1/8 of an inch deep..! also the white wire on j-761 on right amp where The -46vdc rail comes out it runs directly to the + side of that damaged main cap
     

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  9. Marc1234

    Marc1234 New Member

    Messages:
    33
    Sounds good I will let it sit in the warm California sun tomorrow on and running for an hour or so then hit it with spray on all devices and see what I get
     
  10. willyrover

    willyrover Super Member

    Messages:
    3,120
    Location:
    Hamilton
    That capacitor is the filter capacitor for the negative rail. The white wire probably runs to the NEGATIVE side of the cap and the jumper between the caps is connecting the POSITIVE to the NEGATIVE of the other cap.

    The puncture shouldn't be causing your symptoms. It's providing -46VDC to the board. Something on the board is passing it directly to the output.
     
  11. willyrover

    willyrover Super Member

    Messages:
    3,120
    Location:
    Hamilton

    You really only need to let it run until the fault appears, then start the freeze spray aiming to isolate an area of the board where the fault goes away.
     

     

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  12. Marc1234

    Marc1234 New Member

    Messages:
    33
    Ok I will do this hopefully tomorrow I have been helping a buddy move some horses
     
  13. Marc1234

    Marc1234 New Member

    Messages:
    33
    Ok I have pulled all devices again tested each out of circuit ALL tested GOOD re-flowed entire board tested with main outputs OUT same result only this time it starts at -0.02vdc them jumps -46vdc after a few minutes then after a few more minutes it drops back to -0.02vdc and will hold for a few minutes then jumps again it did this constantly over the hour I observed it freeze spray did nothing that I could see any thoughts on where to start replacing devices and is there a chart for replacements somewhere
     
  14. willyrover

    willyrover Super Member

    Messages:
    3,120
    Location:
    Hamilton
    At this point I'll have to admit defeat. I would need to poke around on the actual board to go any further. I also don't know enough about the individual functions of the transistors in the circuit to really know what to start replacing first.


    I will say, if I had parts on hand to swap in, I would probably start by replacing all the diodes and zeners because they are cheap and easy to eliminate as a problem.

    Then, I would continue with H759 only because, if shorted, it would provide a path for the -47VDC between J761 and J757 through a couple of low value resistors. After that I would work my way back through H755, H757, H767 as they affect only the negative rail.

    I am NOT sure if any of the devices on this section of the board need to be matched between pos and neg rails.

    Hopefully someone else can pick up from this point.
     
  15. Marc1234

    Marc1234 New Member

    Messages:
    33
    yea I had my eye on h-759 I think at this point I’m going to just start with h-758 and h-759 any suggestions as to a replacement and I should replace both as a set correct.?
     

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  16. willyrover

    willyrover Super Member

    Messages:
    3,120
    Location:
    Hamilton
    Not sure about what would make a good substitute. Maybe start another thread with that specific question. I'm not sure which ones are REQUIRED to be matched pairs.
     

     

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  17. Steven Tate

    Steven Tate AK Subscriber Subscriber

    Messages:
    2,855
    Location:
    N. Richland Hills, TX
    These transistors are long out of production. This doesn’t seem like a place to shotgun. Did either transistor test bad?
     
  18. Marc1234

    Marc1234 New Member

    Messages:
    33
    So after some unorthodox testing indeed h-759 has some issues any recommend replacements and if both h-758 and h-759 need to be replaced as a complementary pair
     
  19. willyrover

    willyrover Super Member

    Messages:
    3,120
    Location:
    Hamilton
    What sort of issues?

    I would suggest posting your specific question about substitutions in the DIY forum if no one replies here.
     
  20. Marc1234

    Marc1234 New Member

    Messages:
    33
    Got it cold on dry ice with meter on tests great all the way until at or about 200 degrees it fails then I would put it back onto the dry ice after about 30 seconds it starts to work again so I’m assuming it’s an intermittent failure and the air can flipped upside down just wasn’t cooling it enough.? I have searched for this problem elsewhere here on AK but cannot seem to find anything which I thought was odd as it should have happened to someone else by now you would think.? Will start a new thread thanks for your trouble shooting help will update this thread after replacement with outcome unless you have any other thoughts
     
    Last edited: Jun 24, 2018

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