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Selmer TnB 100 runs quiet

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  • #1

    Selmer TnB 100 runs quiet

    Hi all,

    I've recently done some work on a Selmer TnB 100 and now it sounds great but runs a about half as loud. I recapped all the electros and decouplers, put in new diodes in the bias and rectifier (1n5406's, 2 in series per side), and added individual screen grids rather than the 1 per pair as stock. Any ideas as to where I've gone wrong?

    Cheers.

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  • #2
    thats a decent schematic to work from - are the voltages reading similar to the schematic?
    HTH - Heavier Than Hell

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    • #3
      Is it low on gain, eg vol on full and the power amp isn't working hard, or that it's low on power, eg the power amp is overdriving without the expected sound pressure level?
      A friend has got one of those, used for bass; only gets about 80 watts, it compresses early as all the HT current goes through the choke, resulting in a lot of 'sag'. Pete.
      My band:- http://www.youtube.com/user/RedwingBand

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      • #4
        Half as loud means you're only getting 8 watts instead of 80 though.

        My money would be on one of the preamp decoupling caps fitted backwards. There isn't enough current to explode a reversed cap, so the preamp voltages will just be very low, and the volume and gain also. As already suggested, check all the DC voltages against the schematic.

        Another possibility: when you installed the new screen resistors, did you wire them right? If you connected them to the wrong pins on the tube sockets, it wouldn't make much noise.
        "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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        • #5
          Hey guys, thanks for the replies.

          I'm not in the workshop till monday now so I can't check it till then but here's the details I remember.

          The amp itself sounds great. Operates exactly as it should, just half the level of how it was before I did the work.

          The decoupling caps i used on the pre were these Vishay | Passives | Capacitors | Plastic Film | Metallised 100°C |MKT1813-347-405 which as far as i know can't be installed the wrong way around?

          The screen resistors were wired from pins 4 to 6, then all the 6's were wired in series. Finally on pin 6 of a single socket, I wired the two wires (to Output CT and Filter Caps).

          Thanks for your help, its muchly appreciated.

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