1974 Fender Twin Reverb

The Silver-Panel Twin Reverb from the mid-seventies is unique in the Fender line-up both for it’s high wattage power and for the master volume which is sometimes maligned by purists.

The amp was given a full restoration. This amp was already somewhat restored by another tech, but not all of it was done right and some things needed correcting. All filter/bias/bypass caps were replaced with upgraded voltage and temperature rated MOD/Sprague brand electrolytic’s. New 2 Watt Metal Oxide/5 Watt Cement power dropping resistors were installed for better reliability and lower noise floor. The cathode resistor for the Reverb section 12AT7 driver was replaced with a 3 Watt Cement 470 ohm type due to heat damage. All screen resistors replaced with 3 Watt Cement. The Treble pot was replaced with an Alpha brand 250Ka as it was broken. The Input jacks on the Normal channel and the respective Impedance network were replaced with Switchcraft Jacks and Carbon Comp resistors - what was there was not original, used cheap parts, and was wired incorrectly. One of the Speaker Output jacks was replaced for the same reasoning.

The Bias Supply was given my standard modification to be an Adjustable Fixed Bias control rather then the original Balance control - this allows the power tubes to be set to idle at the correct current/voltage. The original tubes did not test good and were all replaced: V1 = JJ12AX7S, V2 = JJ 12AX7MG, V3/V6 = EHX12AT7, V4 = JJ12AX7S, V5 = SOVTEK 12AX7WA, V7-V10 = JJ 6L6GC Matched Quad. The Bias was set to %64 Plate Dissipation with a B+ of 431VDC. A new 3 prong AC cord was installed due to the original being damaged. The Death capacitor was deleted from circuit for safety reasons.