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Sunn SA21 troubleshoot

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  • Sunn SA21 troubleshoot

    Greetings, This amp went into distortion and was immediately turned off. Hooking up to my light bulb limiter and variac I noticed the amp was drawing a lot of current. All output transistors check good out of circuit, but bad in circuit. The filter supply caps read ok with a simple resistance check. The cooling fan was not working, but when I tested it out of circuit it worked fine. By disconnecting the primary lead to the transformer ( at the on/off switch/ fan also connected there) the fan worked fine in circuit. Resistance between the primaries is 0.5 ohm. Primary leads to chassis is OL on both. All insights appreciated. thanks drewv

  • #2
    The rectifier is bad. I will update when I get it replaced.