FENDER BANDMASTER TFL5005D REVERB MOD

Tree tubes (one formerly 12AX7 tremolo, one 12AT7 reverb driver, and one 12AX7/7025/Ecc83 reverb-recovery).

Three unused dials (formerly reverb, speed and intensity) Now we have a amp quite similar to the old Bassman: two more or less identical dry-channels, in phase (so you can use the 'bridged'). We remove the whole mixing stage with the all resistors and the 1/2 12AX7 and wire up the former 'vibrato'-channel identically to the 'normal'-channel- Both now mix via a 220k resistor before entering the phase inverter. Since now the mixing-result is pretty weak, it is amplified with another triode-stage (1/2 12AX7 or 7025 or ECC83), so it is about the same level compared to the 'normal'-channel. Since the reverb-return signal is quite weak compared to the channels dry signal, the dry signal is attenuated by a rel. Now we make out first major change: We get rid of the 'mixing'-stage of the 'vibrato'-channel: Before the two channels ('normal' and 'vibrato') are combined to be passed to the phase-inverter, the 'vibrato'-channel is mixed with the reverb-return signal (wich comes out of the reverb-recovery-stage). Since the tremolo is nothing than a resistor in-between the 'Vibrato'-channels way to the 'mixing'-stage before the signal enters the phase-inverter, at this point our amp still works as it used to work before (without the tremolo)(but still with the reverb as it was). We are later going to connect the tube to the other preamp-tubes anode-voltage-supply). All components on the board except of the tube itself can be removed, even the tubes anode-connections (in the AB763-style circuits the tremolo tube is supported with a different voltage than the other preamp tubes. The resulting circuit can be described as amp with two identical dry channels (like the bassman), and one of them has a fender-reverb-unit all the way before the input (as it would be if it was an external unit).įirst we are getting rid of the tremolo section. The only major difference to the 6G15 circuit is, that we are going to keep the already existing reverb-driver-unit of the AB763-style circuit, wich is the 'parallel' 12AT7 and the onboard transformer (the original 6G15 circuit uses 6K6 pentode and its appropriate transformer).

FENDER BANDMASTER TFL5005D REVERB MOD

In short terms, the mod is about taking out the somewhat noisy and disappointing (compared to the 'harmonic-vibrato') tremolo circuit of an AB793-based amp (as most of the classic Fender amps are) and using the space on the board as well as the two 'vibrato' dials, to incorporate the circuit of the Fender-Reverb-Unit (the 6G15 circuit) with 'Dwell, Mix, Tone' Controls. I am talking about changing/replacing major parts of our amps circuit. This mod is not about swapping tubes or dialing in some 'special' settings. If you are not familiar with either of these, stop reading here (or learn both of the earlier mentioned before you lay hand on your amp, or ask a trained technician to do the what is described in the following paragraphs.).

The following mod requires skills in reading and understanding schematics as well as as knowing and following the necessary precautions in working with high-voltage equipment such as tube amps are. Since it uses the onboard driver-tube and transformer, it wont be a 100% match to the classic unit, but judge for yourself, a sound sample is attached (dilettante (me) with a strat in neck position (pickup, not strap-length!)). This mod can be applied to all AB763-style amps. I want to share a cheap (less the 30 euros/dollars) and feasible way to incorporate the beloved Fender-Reverb-Unit sound into your BF/SF Fender Reverb amp. This is my first post here, so hello to everyone!

Fender bandmaster tfl5005d reverb