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Thread: Electrophone PSA 123 circuit ?

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    Default Electrophone PSA 123 circuit ?

    Hi All,

    After 34 years if service my old GME power supply has given up the ghost. I am going to attempt a repair as it looks the size seeable for an old bloke with a size 10 soldering tip. My circuits have long since been disposed of & I could re-invent the wheel or be fleeced for $120 for a new one. but it would be nice to fix something for a change.
    Many thanks in advance.



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    Thanks gents; I keep an eye open for access.

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    Quote Originally Posted by Softek2 View Post
    Thanks gents; I keep an eye open for access.

    Apols - google keep switching things up ~ you should be good to go

    edit: to avoid any further disappointment ;

    Last edited by wotnot; 11-01-21 at 10:50 AM.

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    Firstly; Thank you for a circuit that is a good size to read & no multi legged IC's. I will spend some time over the weekend with the multimeter. There is 13.6VDC on the output & it will run a receiver (350ma). Just wont take a load. I will fish about & try to find an acceptable load for testing. Many thanks once again & I will keep everyone posted when finished.

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    No worries ~ had a power outage here this morning thus couldn't attend to this until now --- the circuit schematic is taken from the service manual, which you will no doubt find useful ; I'm pretty sure the following link will take you to that ;


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    I will make a guess.
    RV4 The current limit adjust pot is dirty/open circuit.

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    I will make a guess 2n3055 phukt
    reject religion for the planets safety

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    Quote Originally Posted by hinekadon View Post
    I will make a guess 2n3055 phukt
    As it still regulates the voltage, the only way the TP3055 could be faulty would be Collector Base open circuit. Unlikely.
    As RV4 sets the current limit, if the wiper has gone open circuit the current limiting will kick in early.

    Fun guessing.

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    disagree politely when a 2n3055 goes legs up it will become a resister therefore allows a small amount of current thru to tht out put and can be measured as such as thruput from emmiter to collecter without base current /voltage
    reject religion for the planets safety

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    Quote Originally Posted by hinekadon View Post
    disagree politely when a 2n3055 goes legs up it will become a resister therefore allows a small amount of current thru to tht out put and can be measured as such as thruput from emmiter to collecter without base current /voltage
    Different experience. They are usually collector emitter short circuit. Occasionally base emitter open circuit.
    Collector emitter open circuit would let the driver become the main voltage and current path still allowing voltage regulation.
    Still think it is a fault in the current limiting section.

    Still fun guessing.
    Last edited by Reschs; 16-01-21 at 08:51 PM.

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    Still fun guessing.
    It's a guessathon? Awesome! Let me spin the bottle...and......and...... thermal fuse has failed and turned into a resistor

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    Quote Originally Posted by wotnot View Post
    It's a guessathon? Awesome! Let me spin the bottle...and......and...... thermal fuse has failed and turned into a resistor
    Actually, because of Q3's base emitter junction, the 5 Amp fuse blown would explain it.

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    I like guessing games.. I'll have a spin of the bottle and say it is a user error. lol

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