Technics SU - CH7

Discussion in 'General Electronics Chat' started by mossy0853, Sep 7, 2014.

  1. mossy0853

    Thread Starter New Member

    Sep 7, 2014
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    Hello all. I just signed up so not sure what to expect or if I've done this correctly or not.
    I'm trying to repair my mothers aging Technics mini system which she loves and has had since new many years ago!
    I think the problem is the CH7 amplifier as the transformer gets very hot and after a couple of songs on the cd the power goes. If we leave it 10 mins it will fire up again but with the same result a few minutes later.

    It would be a real shame to bin the whole system as she loves it and the rest of it still works fine and sounds great.

    Any ideas on how to sort this problem, or where I could find a replacement?

    Many thanks in advance. Mossy
     
  2. ISB123

    Well-Known Member

    May 21, 2014
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    Check the voltage regulator.Maybe its entering in thermal shutdown mode.
     
  3. MrChips

    Moderator

    Oct 2, 2009
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    Welcome to AAC. You have come to the right place. There are many members here with extensive experience in fixing electronic equipment especially home sound systems. They will be more than happy to lend a hand. That's what gives them their kicks, so to speak.

    To begin, tell us the make and model number of your system.
    Also where you are located and how handy you are at fixing electronics.
    Eventually we'll need to know what test equipment you have and how handy you are with a soldering iron.

    Edit: Is SU CH7 the Technics model number? Ok, got the circuit schematics.
     
    Last edited: Sep 7, 2014
  4. bertus

    Administrator

    Apr 5, 2008
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  5. mossy0853

    Thread Starter New Member

    Sep 7, 2014
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    Thanks Mr Chips,
    Many thanks to all;

    The model number on the back is; Technics steroe intergrated amplifier. SU - CH7 CB -K
    The serial number is FM1GB13021
    We live in Cheshire, near Nantwich.
    I'm a complete novice with no equipment I'm afraid but am prepared to pay someone who does know what they are doing, in order to get it going again.
    Alternatively I would consider buying a replacement, if there are any around.

    Mossy
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Open up the unit to expose the big heat sinks then carefully set it back together so nobody can get hurt when you plug it in. Let it run until it cuts out. Unplug it and quickly open it up and try to find if one of the two big heat sinks us warmer than the other. If so, touch the three components screwed to the heat sink (big module is bass amplifier, smaller on on the right is tweeter amp and small on the left is voltage regulator). If one is exceptionally not, it likely short circuited internally as a short. It needs to be desolder end and replaced with exact duplicate if available.

    If one heat sink is not significantly warmer than the other, then look for some dark marks on the pcb which means something else is getting warm.

    Also look for a capacitor (metal cans looking things). One might have a small opening on top - they pop open when over heated. Overheating can happen as they age, dry and loose efficiency.
     
  7. mossy0853

    Thread Starter New Member

    Sep 7, 2014
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    Many thanks - I'll give it a go.

    rgds

    Mossy
     
  8. MrChips

    Moderator

    Oct 2, 2009
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    If you have some time and patience we may be able to pin-point the fault.

    When you leave it for 10 mins, do you turn off the power? Or do you leave it alone and in comes back on automatically?

    There is a fan in the unit. Does the fan operate?
     
  9. ISB123

    Well-Known Member

    May 21, 2014
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    Can you measure the voltage from voltage regulator?
     
  10. MrChips

    Moderator

    Oct 2, 2009
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    Not likely. OP says he has no test equipment and I suspect OP doesn't know where to find the voltage regulator.

    Let's wait for the OP to respond and take one step at a time that the OP can handle.
     
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