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    Outstanding information!! Thank you very much!!...

    Outstanding information!! Thank you very much!! Nice run of tests for calibrating the mics also including the schematics for the test gear. Amazing!!
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    So this is the schematic i am going to build from...

    So this is the schematic i am going to build from using the second schematic listed.
    46867
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    Not much info. But i did find this....

    Not much info. But i did find this. http://recordinghacks.com/pdf/sennheiser/MKH-415t.pdf
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    Sennhieser MKH 815 T Power supply.

    Ok i got these mics some time ago from a couple different sources. I have five of them in total to include
    Two MKH815T complete
    Three MKH415T in various states of disarray.
    Basic same mic with...
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    Yet another long winded post. Geez, I went to...

    Yet another long winded post.
    Geez, I went to my local electronics spot in Toronto and they don't have 33uf 100v caps. They have them on order but could take a while. Same with any online orders,...
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    I have added an updated drawing of the amp board...

    I have added an updated drawing of the amp board schematic. I think i have it correct. If anything doesn't look right please let me know!! I have edited the drawing a few times now!! Im sure it wont...
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    A few updates. I worked my way through the upper...

    A few updates. I worked my way through the upper failed amp board and tried to prove it to the schematic dmeek had posted way earlier in this thread. Fairly time consuming process for a beginner....
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    Disconnected the +-66v supply from both amp...

    Disconnected the +-66v supply from both amp boards and the -23 volts disappears off the transistors and the sp relay click on. Still have -66 and +49 instead of 44v now straight out of the supply...
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    I have 26 volts at the speaker out. Ruled out the...

    I have 26 volts at the speaker out. Ruled out the speaker relay after bypassing. It was doing its job and was not leaking anything back to the transistors. So, with the 55v transistor supply pulled,...
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    Found the problem, One 33k resistor open on the...

    Found the problem, One 33k resistor open on the suspect amp board. So fixed it and bench tested it for hours so i was pretty happy but when i tried to put it all back together something happened...
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    OK good call. I did that test as you mentioned...

    OK good call. I did that test as you mentioned above on the outer legs of the transistors. I get the same readings on all four amp boards. They all measure about 275 across the two outer legs and the...
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    I meant to ask if those tests i just did tell...

    I meant to ask if those tests i just did tell anything at all about the transistor health or if there is a better way of doing it. I could pull them and test them on my multi function tester but its...
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    Checked the AC ripple and there is none. Scope...

    Checked the AC ripple and there is none. Scope shows a nice clean DC signal on all four amp boards. Other than the positive on the left side shows +44v instead of +66 and we know the upper amp board...
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    Diagram (corrected twice now) 46242

    Diagram (corrected twice now)
    46242
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    So in the M 800 there are four amp boards, two on...

    So in the M 800 there are four amp boards, two on each side of the amp, or two amp boards on the left and two amp boards on the right. There is a pair of 1216`s and a pair of 2922s on each amp...
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    OK, So interesting. Disconnected the lower amp...

    OK, So interesting. Disconnected the lower amp board -66 and the+44 (should be 66v) volt lines and had the scope wired to the speaker as before and the top amp sends signal through to the speaker so...
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    Did that. I got the same readings as before. -66v...

    Did that. I got the same readings as before. -66v on both the orange wires to both top and bottom amp boards but only +44 volts to the blue wires on both. Of course we know the good side of the amp...
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    I was thinking because the amp has two amp boards...

    I was thinking because the amp has two amp boards on each side (one for positive and one for negative) perhaps the board that provides signal the ground side of the speaker is not functioning so the...
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    OK something happened and i cant explain it. So,...

    OK something happened and i cant explain it. So, i was doing a few tests with my scope (old Tektronics 456) At one point i put the probes on the speaker and all of a sudden the amp starts working and...
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    Trying to pick my way through that schematic...

    Trying to pick my way through that schematic dmeek posted. Im not very good at this stuff but i am trying to verify the schematic one part at a time. Output stage seems to map out as per the...
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    The schematic seems quite similar and yes V2+ is...

    The schematic seems quite similar and yes V2+ is the +66v supply or in my case is showing 44v on the bad side. I added a couple more vids for a total of 7 vids on this topic now.
    #5...
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    Everything is hardwired. The amp is split into 2...

    Everything is hardwired. The amp is split into 2 separate sections with separate PS's for each side. The only common thing might be the big power transformer but everything after that is like two...
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    I made a drawing of one the four amp boards that...

    I made a drawing of one the four amp boards that i will post. Not complete LOL but its where im at thus far. I pulled the good side apart as well so i can start testing between the two. The one thing...
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    Well, nix on the relay . It was fine, so back to...

    Well, nix on the relay . It was fine, so back to checking out the amp boards.
    I have no idea how to check transistors in circuit with the amp on but i noticed i have around 57 DCvolts +/- going to...
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    Couple more vids of taking it apart....

    Couple more vids of taking it apart.
    https://www.youtube.com/watch?v=pq_3-c2NN6c
    https://www.youtube.com/watch?v=1F0Kyjp6Be0
    So everything seems to check out in the power supply I got 55volts +/-...
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    Hey guys, Been a while. Like a whole year. last...

    Hey guys, Been a while. Like a whole year. last time i was spending time on this forum my GS3000 console went down which side tracked all other repair projects. Finally got that fixed and then summer...
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    I thought i would update. The problem ended up...

    I thought i would update. The problem ended up being the MPU Eprom and it needed to be re seated. Once doing that a couple times, the mixer now fires up properly. So memory was corrupting due to...
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    Well its been about a week or so since i last...

    Well its been about a week or so since i last worked on this amp. Still waiting for a J111 and a 4560 op amp.
    In the meantime i have been using it for several hours a day and done a few sessions...
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