Yamaha MX2 amplifier issue

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warlocks1
warlocks1 Posts: 1,212
in Basic Hookup/Wiring Questions
I have an old Yamaha MX2 amplifier I am using to drive a set of SDA 2B.

The amp is fine until I pause the music for 5 or so minutes. After I resume playback, there is no sound from the amp. I have to turn it off for a few minutes before it will play again.

Any ideas why?

Thanks
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  • SeleniumFalcon
    SeleniumFalcon Posts: 3,490
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    The European version of your amplifier has a standby function. Do you know if your unit is the USA or European version?
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  • warlocks1
    warlocks1 Posts: 1,212
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    It has a hard wired 120 volt plug so I assume it's USA unless someone modified it.
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  • skipshot12
    skipshot12 Posts: 999
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    What does the nameplate say?
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  • skipshot12
    skipshot12 Posts: 999
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    After I blew my Phase Linear 400 II I purchased a Yamaha MX1000U. It had that info on the nameplate as to voltage & hertz.
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  • warlocks1
    warlocks1 Posts: 1,212
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    States 120 volts 440 VA 340 watts 60 hz
    Made in Japan
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  • SeleniumFalcon
    SeleniumFalcon Posts: 3,490
    edited March 2023
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    That would indicate it probably doesn't have a standby feature. Is the amplifier warm to the touch when you stop playing for 5 minutes? Was it being played fairly hard at that point?
    It could be related to a misbehaving thermal protection circuit. Kind of like the polyswitch problem in some speakers, the protection system is tripping sooner than it originally did.
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  • SeleniumFalcon
    SeleniumFalcon Posts: 3,490
    edited March 2023
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    From the amplifier's service manual here is the section of the schematic dealing with the protection circuitry:

    ubon89z2e0ub.png

    In the upper left hand corner you can see two relays that are in series with the left and right outputs. If you follow the dashed lines they lead down to the right where they are located as part of the protection circuit.
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  • warlocks1
    warlocks1 Posts: 1,212
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    Amp never gets warm. I can play it a low volume and after I pause for a few minutes and then no sound. All the from panel lights are still lit.

    Relay's are way above my skill set, but I will take a look.

    Thank you for taking the time to provide your expertise.
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  • SeleniumFalcon
    SeleniumFalcon Posts: 3,490
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    What device are you pausing? Have you tried different sources?
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  • warlocks1
    warlocks1 Posts: 1,212
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    Yes. It doesn’t matter. I’ve tried 3 different receivers pre outs and different sources. If I pick up the front of the amp a couple inches and drop it then turning off and back on, it will play again. Same thing as my old Denon AVR-4520. I heard the Denon was a mechanical relay? Very odd. I’m about to just get rid of it and get a new amp
    Thanks
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  • F1nut
    F1nut Posts: 49,795
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    Bad relay, cold solder joint or a loose connection. Any of those should be an easy fix for a tech.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • warlocks1
    warlocks1 Posts: 1,212
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    Thanks. Any tech recommendations? I’m in Delaware but can come easily to Maryland
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  • F1nut
    F1nut Posts: 49,795
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    There must be someone in Delaware. If not, try Just Audio in Essex, MD.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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