1994 Fender 59’ Bassman

This is a re-issue of the famed Tweed Bassman 5F6-A circuit produced by Fender in the late 1950’s. These 90’s re-issues are not exact copies however - the lack of a tube rectifier (in most of them but not this particular example), heavier filtering in the power section, V1 changed from a 12AY7 to a 12AX7, and the move from 5881’s to 6L6GC’s separate them from their predecessors . The biggest change in construction though is the move from hand-wired to PCB format. The customer who owned this amp wanted it restored and also taken back to early edition 5F6-A specs, so we modded it to be just like that in all the ways that matter. This was not a teardown and rebuild into hand-wired format, just making the actual electronic circuit and tube lineup compliant with the actual Tweed Bassman design. The amp also needed a full cap job and other repairs - so we took care of all of it at once.

All filter/bias/bypass caps were replaced with upgraded voltage and temperature rated MOD/CE/Nichicon brand electrolytic’s - these were changed in value to represent 5F6-A spec. New 2 Watt Metal Oxide/1 Watt Carbon Film power dropping resistors were installed for better reliability and lower noise floor. The resistor for the V3 (Phase Inverter) cathode was replaced with a 2 Watt 10k Metal Oxide type unit for 5F6-A specs. The resistor for the tone stack slope position was replaced with a 1/2 Watt 56K Carbon Film type unit for the same reasoning - as well as the .1uf 400v film cap in the tone stack, this was changed to .022uf 400v. New 470 Ohm 3 Watt Cement resistors were installed for the screens of the power tubes for reliability reasons. Amp had one new 1/4" jack installed and the input circuit was re-wired to remove poorly installed mods done previously. All other previous mods were removed for the same reasons. New chassis screws and back panel hardware were installed to replace broken/stripped originals. Amp was cleaned, pots treated with De-Oxit, and hardware tightened.

The original tubes did not test good and were not in line with the Tweed Bassman spec we wanted from the amp, they were replaced: V1 = JJ 12AY7, V2 = JJ 12AX7S, V3 = EHX 12AX7, V4/V5 = JJ 5881 Matched Pair, V6 = JJ GZ34. These tubes were picked for best tone, and reliability, specifically for this circuit. The 5881's Fixed Bias was set to Factory Spec.