Augustica
®
T e c h n o l o g i e s
Page 7 of 7
Before testing the headphone amplifier Corvette
®
, visually inspect the PCB for breaks in
symmetry between the left and right channels.
T
ESTING
First, attach only the low voltage filament power supply’s transformer windings to the
terminal block K3, leaving the high voltage transformer leads unattached and electrical
tape shrouded. Do not install 6922 tubes in their sockets.
Second, if you are using a variac, slowly bring up the low AC voltage, while looking for
smoke or part discoloration or bulging.
Third, measure the filament voltage regulator's IC2 LD1084V output voltage without and
with a load. If the filament voltage regulator LD1084V fails to regulate, try either
lowering the DC filament voltage a tad, or increasing it a tad, for example try 10 Volt
instead of 11Volt, as the 1 Volt difference might be enough to bring the regulator back
into regulation. Power down the filament bus of the power supply by disconnecting low
voltage filament transformer or variac.
Fourth, attach the high B-plus voltage transformer or variac windings to the terminal
block K2 and slowly bring up the high AC voltage, while looking for smoke or part
discoloration or bulging.
Fifth, measure the B-plus voltage provided by the MOSFET transistor IC1. If you applied
220 Volt AC to the terminal block K2, the power supply should deliver about 320 Volt
DC without any load measured at the MOSFET transistor. If the headphone amplifier
Corvette
®
is attached to the B-plus bus of the power supply, the power supply should
deliver 270 - 280 Volt DC depending on resistance of the load.
Sixth, measure the voltage across ground and B-plus pads of the PCB. If the two channels
differ by more than 10 VDC, try switching 6922 tubes from one channel to the other. If
the imbalance does not follow the tubes, there is a problem, probably a misplaced part.
Only after you are sure that both filament and B-plus power buses are working properly
should you attach the amplifier Corvette
®
to a headphone.
L
ET
U
S
K
NOW
W
HAT
Y
OU
T
HINK
If you would like to see some new audio PCB or kit or recommend a change to an
existing product, drop us a line by e-mail on the website www.Augustica.com (begin the
subject line with “Corvette” or the spam filters are sure to eat your message).
