studiomaster vision 8

Discussion in 'Electronics Repair' started by dylanthermos, May 19, 2011.

  1. dylanthermos

    dylanthermos

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    Hi all, I'm new to repairing electronics so I was wondering if some of you knowledgable folk could kindly help me?
    I have been given a Studio master vision 8 amp/mixer for PA use.
    I have opened it up and found what looks like a transistor called T3 on a board named R1A1-4.
    I will attach a photograph of suspect component.
    I used to be a telephone engineer so have used a soldering iron quite a lot.(mainly cable jointing)
    Before I take the whole board out to renew this component is there any one out there who has dealt with this before?
    If there is do I need to renew any other components whilst it is open on my bench?
    Also where can I get this part, I'm living in Swansea Wales, UK.
    ..........Thanks for any help..........dylanthermos.

    Attached Files:

    dylanthermos, May 19, 2011
    #1
  2. dylanthermos

    (*steve*) There is no spoon! Moderator

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    Why do you suspect this component?

    And how have you determined the correct replacement -- the part appears to have no markings?

    To replace this transistor, simply undo the bolt (or whatever) that is holding it down, then use some solder wick or a solder sucker to help remove the solder. Insert a new part, bolt it into place, and solder the leads.

    There appears to be a hint of some slight discolouration of the board under the transistor, but this is not necessarily an indication that it has failed.
    (*steve*), May 20, 2011
    #2
  3. dylanthermos

    dylanthermos

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    I suspect this component because the circuit board under this component is scorched.
    This appears only here.My photograph is not that good but also it says TR3 printed on the board next to the part.I assumed this to be its name?
    The black dome shaped button on the top of the transistor disintegrated when I tried to see if it was bolted down. I was a plastic/bakerlight material that just crumbled.
    I also assumed that this was because it had endured too much heat.
    I know nothing about doing this type of repair but am prepared to have a go, what have I got to lose this mixer desk is standing idle.
    Where would I acquire this part? Would you kindly suggest a supplier?
    Thanks for taking time to reply I really am grateful.......dylanthermos.
    Please see extra pic below.......
    Last edited: May 20, 2011
    dylanthermos, May 20, 2011
    #3
  4. dylanthermos

    dylanthermos

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    Another angle pic

    Another angle of pic

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    dylanthermos, May 20, 2011
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  5. dylanthermos

    (*steve*) There is no spoon! Moderator

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    There's nothing written on the device. It could be almost anything.

    You need to find a service manual which may have more information.
    (*steve*), May 24, 2011
    #5
  6. dylanthermos

    (*steve*) There is no spoon! Moderator

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    OK, have a look here.

    There is a schematic for a StudioMaster Powerhouse Vision 908. I don't know how closely these are related. If you are lucky they may hare similar circuitry and you may be able to find something useful here.
    (*steve*), May 24, 2011
    #6
  7. dylanthermos

    (*steve*) There is no spoon! Moderator

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    Check page 3. This looks like the fan control. That transistor would be a TIP30.

    I can't see that a failure here would cause your symptoms. It may cause the unit to overheat though. Does the fan operate?
    (*steve*), May 24, 2011
    #7
  8. dylanthermos

    dylanthermos

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    Hi Steve, I have'nt run the mixer amp for a while. Last time I did the power light came on but I don't remember a noise from a fan. Perhaps it won't start running till it gets up to a certain temperature?
    I'll strip it down again and be very careful as to what I touch whilst it is open.
    I'll use headphones so that it doesn't have to be connected to a pair of speakers.
    I'll come back to you in a few days cos today is "She who must be obeyed's" birthday.
    Speak soon........dylan.
    So will probably be tomorrow or next day.
    dylanthermos, May 24, 2011
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  9. dylanthermos

    dylanthermos

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    Well managed to power up the mixer amp but the led's did not light up.I could hear a power hum when I had the headphones but no fan sound, so next job will be to go to Maplins and get a transistor TIP30.
    When that is in my possession I will let you know.
    Then I can do the hard bit and replace it.........thanks will keep you informed.....dylan
    Not saying that this will completely restore it to full service.......
    dylanthermos, May 25, 2011
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  10. dylanthermos

    (*steve*) There is no spoon! Moderator

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    There seem to be a couple of signals which turn on power to the fan. It is quite possible that neither of these is asserted and this is why the fan is off.

    It may be a red (or in this case black) herring.
    (*steve*), May 25, 2011
    #10
  11. dylanthermos

    dylanthermos

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    Noticed one of the fuses has blown so will get some of those whilst at Maplins.
    Been to Maplins got fuses but not the component I require.
    Will try another local supplier today.........thanks dylan
    dylanthermos, May 26, 2011
    #11
  12. dylanthermos

    dylanthermos

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    TIP 30C

    Hi Steve, I have removed the part and it's a TIP30C.
    Will have to send away for one as I can't get it local.
    The charring looks pretty bad now the part is removed or would this be normal I just don't know not having any experience?
    Thanks again, dylan

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    dylanthermos, May 28, 2011
    #12
  13. dylanthermos

    dylanthermos

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    Have replaced a fuse also, will check all the rest and let you know when I acquire the component ...........dylan
    dylanthermos, May 28, 2011
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  14. dylanthermos

    (*steve*) There is no spoon! Moderator

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    Since you have the device out of circuit now, test it.

    See what the resistance are (in both directions) between each pair of leads.

    If the transistor is OK, you should find one pair reads open circuit (or close to it) in both directions, and the other 2 pairs read open circuit only in one direction.

    Any deviation from this indicated the part is bad (although it may be bad and still exhibit almost normal readings, but this is less likely in a power device).

    Looking at the mounting hole, it is not charred through the board, the discolouration appears to be a surface effect, so this may just be a board that darkens easily. However if there is room to fit a heatsink to the transistor (just a piece of metal that you can place under the transistor then let stand free above it would be fine) then you may well make it a lot happier. Just make sure that it can't come into contact with anything else and short out.
    (*steve*), May 28, 2011
    #14
  15. dylanthermos

    dylanthermos

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    Hi Steve,
    I've just bought a UNI-T ...UT39B multimeter from maplins.
    Not sure which scale to read it from but..........
    When it is in the 20k ohm scale the two outside tags read..4.72
    Left tag and centre tag reads 4.56
    When it is on 200k scale readings are 28.9 outside tags
    26.7 left tag and centre.
    Sorry to be so ignorant of these procedures but as I say I know nothing?
    There seems to be no reading between centre and right tag?
    Does this help in any way?........Thanks again dylan
    dylanthermos, May 28, 2011
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  16. dylanthermos

    (*steve*) There is no spoon! Moderator

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    You need to read it both ways. i.e. red on first lead, black on the other -- then the other way around black on the first lead and red on the second. The readings you have sound like reasonable forward readings for the device. If you don't get any reading for all other combinations then the transistor is probably OK.

    If the multimeter has a diode test function, even better. These normally display a voltage drop, so you would expect to see a value between 0.5 and 0.8 one way, and whatever the meter displays when the leads are not touching anything the other way (for 2 pairs). For the remaining pair, the reading should be the same both ways (as if the probes are not connected).

    OK, when laying on it's back, the leads from left to right go Base, Collector, Emitter.

    The collector is connected to the metal tab.

    between the base and either the collector or emitter you should see conduction in one way but not the other.

    Between the emitter and collector you should see nothing either way.
    (*steve*), May 28, 2011
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  17. dylanthermos

    dylanthermos

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    Hi Steve,
    The meter has a diode test.
    When i connect left tag(Base) and centre(Collector) it reads 728.
    The two outside tags(Base and Emitter) read 735
    I'm not getting any readings when I put red lead on the other way round.
    Is this reading OK?
    dylanthermos, May 28, 2011
    #17
  18. dylanthermos

    dylanthermos

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    New Meter

    Hi Steve here is a pic of the meter I bought.......if it helps at all........dylan

    Attached Files:

    dylanthermos, May 29, 2011
    #18
  19. dylanthermos

    (*steve*) There is no spoon! Moderator

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    That sounds fine. 728 means 0.728 volts. Note that the voltage drop base to collector is slightly less than the voltage drop base to emitter. This is expected.

    I suspect that the discolouration of the board is due to this board being one that changes colour easily rather than a critical problem with this transistor. In any case, the problem (if any) which caused this discolouration would have been unlikely to start in the transistor. I would tend to suspect the fan or even the power supply first.

    Since you have a replacement, you could fit it, but I would not consider it likely to solve the problem.
    (*steve*), May 29, 2011
    #19
  20. dylanthermos

    dylanthermos

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    I have n't obtained a replacement yet so I could reinstall the old component.
    The underside is a shiny metal.This would explain why the board is so charred.
    I can see the fan you are talking about it has a red and a black lead going to it.
    How can I test this to see if it is working?It spins freely now that I have taken all the old dust out of it.
    I would think that I would have to intercept the red wire and strip some sheathing off it and test it both ways through the multi meter?
    What reading should I obtain at this point?
    Will I have to send power to it to test it? Or would it be possible(to test) when there is no power to the unit?
    So many questions, sorry to be a pain.........dylan.
    dylanthermos, May 29, 2011
    #20

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