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peavey transtube supreme no sound

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  • #1

    peavey transtube supreme no sound

    Hello all,
    I just picked up a Peavey transtube supreme head for ten bucks. Obviously it doesn't work. I have tried all the non internal stuff i found online running cable in and out of fx send and return and such. The unit powers on led comes on but I get nothing out of the speaker, I tried different cables. The three fuses are fine. I guess I need a starting point what to check first on so on. I have a meter and have repaired tv's so no problem digging in just need direction. Thanks
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  • #2
    Welcome to the place. Contact Peavey and get a copy of the schematic.

    Start by checking the power supply circuit. If there is no voltage, there is no sound.

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    • #3
      I have the schematic, Where would be best to measure, across the large caps c72, c87. I will start tonight at work right now. looking at the schematic looks like I should get 25 volts across these two caps sound correct.

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      • #4
        Yup. +1

        And to be clear 52 Bill isn't speaking of the input AC mains. Any power supplies that serve voltage to the individual amplifiers, such as +15V and -15V DC supplies.

        Have you tried a different speaker?

        Are there any potential clues like loose knobs, pots, jacks or switches?

        No sound at all. As in, the light is on but it's a dead amp, sounds like a speaker, output jack or it's wiring or output amplifier problem. And of course an output amplifier couldbe having a problem due to no voltage.

        Can you link or post the schematic so we can look at it?
        "Take two placebos, works twice as well." Enzo

        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

        "If you're not interested in opinions and the experience of others, why even start a thread?
        You can't just expect consent." Helmholtz

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        • #5
          http://music-electronics-forum.com/a...-schematic.pdf

          Not sure that will work from another thread, I'll start to look at it tonight thanks for the info so far.

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          • #6
            Oh... this is one of those flying rail designs.

            The 25 volt supplies are for the preamp, the power amp would have much more than that, maybe 55-60 volts. Read the voltage across the two big 2200uF caps, not the voltage to ground. This amp has two different ground returns. Remember that when you are checking voltages.

            And as Chuck mentioned if you haven't already done it, check the speaker, etc. The speaker negative is connected to ground through a resistor, check that resistor and its solder joints. The speaker positive connects through a thermal circuit breaker. Check the wiring and the breaker itself for continuity.

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            • #7
              Ok will check voltages across those caps tonight as well as check for anything loose and try different speaker cab. What exactly is a floating rail, my assumption is that its one voltage that connects multiple points to it. There isn't an actual rail correct. Took electronics in High school been a while.

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              • #8
                Test the speaker THROUGH THE SPEAKER CABLE. If that works, proceed.

                When the amp is flipped on, does ANY sound come out the speaker? Any little pop or thump? ANy background hum or hiss?

                If not, there is something basic wrong. COuld be missing power or open signal path.

                Is there continuity to ground from the cold side of the speaker jack? As Bill mentions, that thermal breaker in the speaker line, does it have continuity? It is on the heat sink.


                In conventional amp designs, there will be a positive voltage supply and a negative one. Each is connected to ground, so if they are 45 volts apiece, then ther should always be +/-45v on them. "Rail" just means a common connection, it does not mean an actual physical bus bar. That would be called a "bus."

                FLying rails or floating rails refers to a different design approach where the two supplys are not referenced to ground, they connect to the speaker. See how on the schematic the place where you might expect the speaker to connect goes instead to ground. So the rails themselves move around with the music - WITH RESPECT TO GROUND. At idle, they should center and look like normal amps.
                Education is what you're left with after you have forgotten what you have learned.

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                • #9
                  ok I checked and there are no loose connections, i also proved out the cables i was using by going through my powered mixer first and they worked. I measured 46volts across the two large caps c72 and c87. Unfortunately i let my meter slip and I beleive that q14 is now gone as it blew the fuse and the replacement I put in. If Q14 was blown would that cause the fuse to blow? Enzo before the fuse blowing there was no pop or hiss or anything from the speaker. I will check continuity on the thermal breaker tonight thanks enzo for poiting out where it is.

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                  • #10
                    Ok I am getting continuity across the thermal breaker and from negative post of jack to ground, any more suggestions where to go from here? Thanks for all your help so far.

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                    • #11
                      Amp is up and running, after I replaced the transistor i blew I found that one of the leads from the thermal breaker was not soldered. i soldered it up and it came to life. Thank you all for you help and sharing your knowledge

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