New project Marantz 2250b

Discussion in 'Marantz Audio' started by pjf610, Dec 23, 2017.

  1. pjf610

    pjf610 Active Member

    Messages:
    140
    Hi all, since i am waiting for a replacement power switch for my 2216b, i am going to start getting into my 2250b So i turned on the 2250b (using a DBT) and it turns on no problem but no sound i did notice that the relay did not switch on, before i start cleaning things up, what are the first steps to see what's going on, I did notice there were no jumpers between the Main and Pre amp so i made up a set yet still no relay turning on. Where do i begin.

    Thanks Pat
     

     

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  2. catrafter

    catrafter Marantz Specialist Subscriber

    Messages:
    6,129
    Location:
    Montana
    My first advice is for you to build a dim bulb tester if you haven't already.

    Tom
     
  3. audiomaniac2

    audiomaniac2 Member

    Messages:
    85
    Location:
    Modesto Cal.
    Check out H701 which is an 18 volt zener diode.Make sure you have 18 volts dc across it.That's a weak link in this model.Also check out R713 make sure it's not burned out.This is on the p700 power amp board,.
     
  4. pjf610

    pjf610 Active Member

    Messages:
    140
    I have a DBT and the unit powers on ok the relay does dot click on should i check the relay first
     
  5. pjf610

    pjf610 Active Member

    Messages:
    140
    Since the relay does not click on and i get 35vcd on that board, doesn't that indicate that there could be something wrong with one of the main amp boards because doesn't the relay protect the main amp??
     
  6. pjf610

    pjf610 Active Member

    Messages:
    140
    OK I started to go over this unit i knew there was a problem when i got the unit!! The first thing after checking some of the voltages was to test the output transistors (I took them off and tested them) the right channel was ok the left had both transistor showing there were shorted, I changed them out with new transistors and when i put the unit back on the DBT VERY BRIGHT light, I am trying to determine were to start troubleshooting, were do i begin???
     

     

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  7. jd3rdcoast

    jd3rdcoast AK Subscriber Subscriber

    Messages:
    162
    Location:
    Houston Area
    Disconnect both amps. Power to see if Relay closes. Then reconnect one amp at a time to see if problem is isolated to one or the other. Hopefully that will get you in the ballpark.

    JD
     
    Last edited: Jan 27, 2018
  8. pjf610

    pjf610 Active Member

    Messages:
    140
    Thanks how would i disconnect the amps???
     
    Last edited: Jan 28, 2018
  9. pjf610

    pjf610 Active Member

    Messages:
    140
    I have a question if I am going to check the H701 and R713 while i have the board out would it be better to change all the cap's since the board is already out????
     
  10. Steven Tate

    Steven Tate AK Subscriber Subscriber

    Messages:
    2,808
    Location:
    N. Richland Hills, TX
    Don’t change anything until you find the problem and fix it. Then go back and recap. Shotgunning before a major problem is fixed just adds more uncertainty since parts placement and soldering can introduce new problems.
     
  11. pjf610

    pjf610 Active Member

    Messages:
    140
    That is what I though just confirming, when you have a problem like this being a newbie and I would love to learn about this what would be the first thing that i would look for ( please look at thread #6)
     

     

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  12. pjf610

    pjf610 Active Member

    Messages:
    140
    I just pulled the new transistors in the left channel and low and behold the light went dim and the relay clicked on I presume that there is were my problem the left channel, I read some of the threads that H701 and R713 had given them problems, I don't want to guess but what should I be looking for next???
     
    Last edited: Jan 28, 2018
  13. Steven Tate

    Steven Tate AK Subscriber Subscriber

    Messages:
    2,808
    Location:
    N. Richland Hills, TX
    What replacements did you use for the outputs? Are you positive you got the NPN and PNP in the right positions?
     
  14. pjf610

    pjf610 Active Member

    Messages:
    140
    MJ21193 MJ21194 and this is the configuration they are placed looking at the heat sink
     
  15. Steven Tate

    Steven Tate AK Subscriber Subscriber

    Messages:
    2,808
    Location:
    N. Richland Hills, TX
    Just to be clear, I’m a relative noob to diagnostics, but I read every thread I can where people are trying to track down trouble. With blown outputs, I see two strategies:
    1. If no visible damage, start pulling and testing transistors from right to left on the schematic. You are looking mainly for shorted transistors. If you find a bad one, check the next one upstream. These things can take out several components downstream when they short. Of course, the first transistor to fail could be the problem, or it could have gone because of a nearby passive component.
    2. If the other channel is good, you can test voltage at the transistor legs on the good side and compare to the bad board. Caution - don’t just poke around with a red probe while the unit is running. Bad things happen. Either use mini grabbers that you insert while turned off, turn on to measure, and turn off to remove, or (a bit more dangerous) cover your probe with electrical tape all except the very tip to probe while unit running. Either way, go right to left on the schematic, measure 3 legs of a transistor on the good board, and then measure same on the bad board, looking for areas where an expected low voltage is very high. That will be a bad transistor, but, again, it may not be the origin of the problem. Hopefully others will chime in and give you more focused advice. Good luck!
     
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  16. pjf610

    pjf610 Active Member

    Messages:
    140
    Thanks for the input, just to confirm what i already did the 2 main output transistors are both shorted i pulled them then tested them i then replace them with the 2 new transistors that is when using a DBT we got a very bright lite, I then pull the new transistors out and turn on the unit again and got the relay to switch on so i think that the problem is in the left channel. So I am trying to understand what you are saying is to check the output transistors that i know are bad or check the other transistors on that board (H701-702-703etc.???
     

     

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  17. Steven Tate

    Steven Tate AK Subscriber Subscriber

    Messages:
    2,808
    Location:
    N. Richland Hills, TX
    First check the new outputs and see if they blew. Then start with the drivers H714 H715 either by pulling and testing or comparing voltages to the good board. After that, predrivers H710 H711. I’m hoping others will jump in and guide you with more expertise.
    Steve
     
  18. pjf610

    pjf610 Active Member

    Messages:
    140
    The new outputs are OK I will start checking out the transistors tomorrow thanks for all your help Steve. Back at you tomorrow
     
  19. jd3rdcoast

    jd3rdcoast AK Subscriber Subscriber

    Messages:
    162
    Location:
    Houston Area
    I can attest to this! Bad JuJu ensues plus added time, expense and frustration. All it takes is one slip w/power on = smoke! Best advice I read, "throw away the probes and buy mini-clips direct to your DMM".
     
  20. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    27,347
    Location:
    uk.. the middle bit
    all i can guess is outputs were mixed up .
    but best check voltages on dbt where the removed outputs connect to . as in emitter base collector . sorry cant make out board numbers in this manual scan .
    this will tell us what is going on here .
     

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