‘68 Custom Deluxe
®
Reverb
(This is the model name for warranty claims)
5
impedance modulation varies the effective input
level that drives the power amplifier.
POWER AMPLIFIER
Phase splitter V6-A&B is configured in a differential
long tailed pair topology with V4-B driving the non-
inverting input and the feedback from the speaker
output attached to the inverting input. Output from
the V6-A drives the upper power amp tube V7. Out-
put from the V6-B drives the lower power amp tube
V8. V7 and V8 act as a push-pull pair in the tube
class A-B power amplifier. T2 matches the 6L6 plate
impedances to the speaker load.
POWER SUPPLY
The line voltage is fed to T3’s primary through the
line fuse, F1, and the inrush current limiter, TH1.
The red secondary output is full-wave rectified by
dual vacuum tube diode V9 and filtered to produce
the 415V (B+), 406V (Z), 324V (Y), and 270V (X)
DC supply voltages for the power and preamp
tubes.
A 6.3VAC secondary (green) powers the power in-
dicator lamp and the preamp & power amp tubes’
heaters.
The rectifier diode filament is supplied by a sepa-
rate 5.4 VAC secondary winding (yellow).
Negative bias for the output tubes is supplied by the
solid state half-wave rectifier CR1, a resistive divid-
er circuit (R69, R58 and R59), and two filter
capacitors (C36 & C29). R58 is used to adjust the
output tube stage bias voltage to nominally set the
V7 & V8 idle currents at 24 mA for each.
