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Thread: Help Marshall vs65r

  1. #1
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    Help Marshall vs65r

    Hi first time here.So a friend of mine give me this amplifier with this problem.No sound noise the volume and any other thing doesn't change the noise.So I noticed that the 2 big resistor(white) on preamp board go really hot.I checked them and the values are ok.So looking on internet someone tells is a problem with the power transistors.I pull them out I checked with my digital multimeter and they both give values under .6v just one pin of the t64a is .623. All the value are different are those transistor gone?Do make sense to make the transistors the wrong components?Thanks

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    0.6V is a good reading if it reads only one way.
    When using the 'diode check' function of a volt meter to check a BJT transistor the meter leads should be set as follows.
    For NPN type: Red (+) lead on Base to (Black) Emitter. (Red) Base to (Black) Collector.

    For PNP type: Black (-) lead on Base to (Red) Emitter. (Black) Base to (Red) Collector.

    All other lead/pin configurations should read open circuit.

    Large resistors are meant to get hot.
    That is why there is a maximum wattage rating on them.
    Measure the voltage drop to see how hot they should be getting. (P=VxV/ R)

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    thanks.Do you have any idea what this amp must need to work?it powers up there is hum and if you move volume nob in both channel nothing happens

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    It could be a bad switch on the FX return jack. Try plugging a jack intio it a dozen time to try to clean the contact, or connect the send to the receive with a lead. Google "Dreaded switching jack problem"

    If that doesn't work you can test the power amp on it's own by plugging your guitar into to the FX return.
    Still nothing? Listen up close the the speaker, there should be a faint hum.
    Still nada? Test the speaker.
    Experience is something you get, just after you really needed it.

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    no the amp went down while playing(not me it's a friend amp).It's not the speakers nor the send fx etc.There's hum on the speakers and sometimes noise

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    Quote Originally Posted by AL78 View Post
    no the amp went down while playing(not me it's a friend amp)
    So? They always work and then stop. You have to do the diagnostics to narrow down the fault. You may well be right in that it's the power amp but you need to be certain otherwise you are putting your effort in the wrong place.
    Tone Meister and SoulFetish like this.
    Experience is something you get, just after you really needed it.

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    nothing changed

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    Hum and noise on the speaker is a good indication that the power amp is OK.

    Have you tried plugging into the FX return yet?

    What about taking the line out to different amp?

    Schematic http://bmamps.com/Schematics/marshal..._vs65r_65w.pdf
    Experience is something you get, just after you really needed it.

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    Of course nothing comes out

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    Quote Originally Posted by AL78 View Post
    Of course nothing comes out
    Seriously AL78. You need to up your game - I can't play guessing games with you. Nothing comes out of what under which test?
    Experience is something you get, just after you really needed it.

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    No sound comes out from the speaker only hum I've done all the test you told me to do again ALL the test.

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    Quote Originally Posted by AL78 View Post
    No sound comes out from the speaker only hum I've done all the test you told me to do again ALL the test.
    What about the line out to a different amp test?
    Experience is something you get, just after you really needed it.

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    As stated before done the test from line out and no sound come out from the othre amplifier

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    OK. Gotcha. Let's measure some DC voltages to ground. I like to use the sleeve of the input jack as a handy ground.

    1) Collector of T9
    2) Collector of T11
    3) TIP of speaker jack
    4) GATE of J111 T16
    5) Pin 4 of IC7
    6) Pin 8 of IC7
    Experience is something you get, just after you really needed it.

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    Thank for your patience.Listen Here in italy is kinda late so I'll do it tomorrow.I kinda new at this for "to ground" do you mean that iI have to touch with my red lead the point you said me and with the black lead the chassis of the amp? I have no idea what's the gate of j111 t 16.Last there is no speaker jack the are faston on the speaker side and the red and black are soldedered on the amp board.

  16. #16
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    Quote Originally Posted by AL78 View Post
    Thank for your patience.Listen Here in italy is kinda late so I'll do it tomorrow.I kinda new at this for "to ground" do you mean that iI have to touch with my red lead the point you said me and with the black lead the chassis of the amp? I have no idea what's the gate of j111 t 16.Last there is no speaker jack the are faston on the speaker side and the red and black are soldedered on the amp board.
    No probs. Had no idea your were from Italy - there might have been a bit of a language issue. It's a good idea to state where you are from in your profile.

    Black lead to sleeve of input jack - I don't trust using the chassis in solid state amps as there any many different grounding schemes. I forgot there isn't a speaker jack on this model - use the red speaker lead - take extreme care not to accidentally short the speaker leads together at any time.

    Look up a datasheet for a J111 and then the pinout you'll see see which pin is the gate.

    j111_pkg.jpg

    HINT: It might be easier to measure the gate voltage at the junction of R34 & R33.
    Experience is something you get, just after you really needed it.

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    Hi I'm going to do it now.Are you sure that is t 16 and not t 13?cause r 34 &r35 are closer to t 13.Anyway I've done it those are the results meter in volt black on input jacket.
    1) Collector of T9 40v
    2) Collector of T11 -40v
    3) TIP of speaker jack -15,8mv
    4) GATE of J111 T16 -26,36v
    5) Pin 4 of IC7 0,910v
    6) Pin 8 of IC7 0(zero)
    I measured Collector of T13 -41v
    Thank you
    Last edited by AL78; 10-13-2016 at 09:01 AM.

  18. #18
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    Quote Originally Posted by AL78 View Post
    Hi I'm going to do it now.Are you sure that is t 16 and not t 13?cause r 34 &r35 are closer to t 13.Anyway I've done it those are the results meter in volt black on input jacket.
    1) Collector of T9 40v
    2) Collector of T11 -40v
    3) TIP of speaker jack -15,8mv
    4) GATE of J111 T16 -26,36v
    5) Pin 4 of IC7 0,910v
    6) Pin 8 of IC7 0(zero)
    I measured Collector of T13 -41v
    Thank you
    T16, I'm sure.

    IC7 has no power:

    Check for power on pins 4 & 5 on those connectors too. If close to zero check CON2 & CON 14 for good contact.
    Check ground continuity by measuring the resistance between CON12 (black lead to the transformer) and the sleeve of the input jack
    Check the voltage on both sides of R17 and R18.
    Experience is something you get, just after you really needed it.

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    Hi on this board there is nothing on r 17 or R18.Pins 4&5(do you men together right?not against ground right) 33.11 v.About the continuity con 12 sleeve input There is.

  20. #20
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    Pins 4 & 5 should be measured relative to ground (on sleeve of input jack)
    Now check pins 4 then 5 relative to ground on CON12 (black lead)
    Check both sides of R17 & R18 - it sounds like you might have check one only one side.






    If you have power at pins 4 & 5 and nothing on
    Experience is something you get, just after you really needed it.

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    Pin 4 against ground is .0910 v
    Pin 5 against ground is 34,26 v
    pin 4 con 12 0,924
    pin 5 con 12 34,26
    There is no resistor on the the board at r17&18 only te holes for the resistors and the numbers and the shape no components.Nobody is ever touched this amplifier so It's impossible that someone removed those

  22. #22
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    Quote Originally Posted by AL78 View Post
    Pin 4 against ground is .0910 v
    Pin 5 against ground is 34,26 v
    pin 4 con 12 0,924
    pin 5 con 12 34,26
    There is no resistor on the the board at r17&18 only te holes for the resistors and the numbers and the shape no components.Nobody is ever touched this amplifier so It's impossible that someone removed those
    Must be a different board rev. What is the part number marked on the board? The schematic I'm looking at is VS65-60-02. Quite often the component reference designators will change between revisions. This is done to make life complicated for everyone. A clear photo of your preamp board might help.


    These resistors are big white ones - probably the ones you mentioned right at the start of the topic.
    (1) Are they the same value, 330 ohms as the ones on the schematic?

    At that time you said they were getting hot, as they should when they are working. That does not tie in with no voltage on IC7. Therefore we need to check the preamp voltage in a few places.


    Do you have ZD1 and ZD2 on that board? - Measure the voltage across each of them.
    Measure the voltage on both sides of the bog white preamp resistors?
    Last edited by nickb; 10-13-2016 at 11:37 AM.
    Experience is something you get, just after you really needed it.

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    Before we waste time.I count the pin of the ic7 1 it's the bottom left and 8 is the top right is this correct?The board is ma vs65-60-00.Sorry I was looking on wrong place offcourse there'are those big resistors I was looking in the power amp board sorry.
    -15v -40v r 18
    33,50v 40,04v r17
    Both Against ground.
    Yes I have zd1 and zd2
    ZD1 15,70v
    ZD2 399 mv

    Here is the reading.Only please clarify me if the reading on the IC7 pins are ok otherwise i'll do it again.I'm not sure about the pin counting thanks you are a trooper
    p.s.
    I've take pics of the board do I post them here?
    Last edited by AL78; 10-13-2016 at 11:37 AM.

  24. #24
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    Quote Originally Posted by AL78 View Post
    Before we waste time.I count the pin of the ic7 1 it's the bottom left and 8 is the top right is this correct?The board is ma vs65-60-00.Sorry I was looking on wrong place offcourse there'are those big resistors I was looking in the power amp board sorry.
    -15v -40v r 18
    33,50v 40,04v r17
    Both Against ground.
    Yes I have zd1 and zd2
    ZD1 15,70v
    ZD2 399 mv

    Here is the reading.Only please clarify me if the reading on the IC7 pins are ok otherwise i'll do it again.I'm not sure about the pin counting thanks you are a trooper
    p.s.
    I've take pics of the board do I post them here?
    You have an early rev of the board. We'll have to proceed with some caution. We may not need the pic now. Read on...

    IC7:

    tl072.jpg


    You have an open between R17 and ZD2. It's probably a bad solder joint on R17.
    Experience is something you get, just after you really needed it.

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    yeah i noticed that there is some black burn in that area.
    Last edited by AL78; 10-13-2016 at 01:27 PM.

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    I forget t add some info.I've already removed either the resistors and those zd1 and zd2 to check they are ok.I've already changed the caps.What I can do?I've already do the soldering on that area.Is that possible that the burnt brake the board in the area and that's why there's an opening?

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    It's very obvious that there is no connection between between ZD2 and R17. The 33.5V voltage on R17 is a concern. Rather than speculate you have to pull the board and see what is going on. Use your meter on continuity "beep" test mode so find out exactly where the open is. I've noticed in the past that leads of resistors that have been running very hot can be hard to solder. They need a good scraping to clean off the oxides and a healthy dose of flux can only help.
    Experience is something you get, just after you really needed it.

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    Hey thank you.Unfortunately all this things are way above my abilities,I'm don't have any idea how to use flux and check any connetions.So I've already put everything back in the enclosure.I think it's the best thing to do thank you for you time at least I've tried.Now it will go back to the friend of mine who gave me.Unfortunately I live in the south and there's nobody who will fix this.They have already told him to trash it so..Thanks

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    If you just ran a jumper wire from R17 to ZD2 it would probably fix it.
    No need to trash it.
    Anyone who does electronics work should be able to do this if they are told which points to connect. It doesn't have to be an amp repair shop.
    nickb likes this.
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  30. #30
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    Don't bail out just yet. You done all the hard measuring and now it's time to reap your reward Don't sweat the flux - I'm just trying to highlight that those resistors leads sometime need a little extra care.

    You can try the wire like G1 said and I might work. If it doesn't, pull the board and have a good hard critical look around the problem area.
    Experience is something you get, just after you really needed it.

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    https://postimg.org/image/rgebxp6wr/

    Ok this is the pic of the board please tell me from where to where and how I do this.I'll try myself.Trust nobody in the city I live or the entire sicily will do that.Everytime I need some help for my reel to reel or cassette deck or speakers I pack them and ship in the north of Italy

  32. #32
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    I can't really tell from that pic. Can you take one from the other side looking toward the caps above the white resistors. A bit better light would help a lot.
    Experience is something you get, just after you really needed it.

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    hei if I take the picture from there you will see nothing.Should I do that from the leg of the resistor closer to zd2 to the zd2 itself?Should the wire goes on top of zd2 or bottom?

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    Wire from the end of ZD2 with the black stripe. I can't tell for sure which resistor is which or which end from that photo.
    Experience is something you get, just after you really needed it.

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    thanks I'll identify the resistor from the numer,but Which side?How I can know for sure?There is any sign on the resistor?

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