StewMac ’64 REVERB UNIT Assembly Instructions Manual page 35

STEP 86
Test the preamp tubes
With the unit unplugged, you can
install both of your preamp tubes .
There are no indexing pins for the
preamp sockets, but there is only
one way to install these tubes in their
sockets .
Af ter these tubes are correctly
installed, plug the unit back in . The
pilot lamp should light up . Let the unit
warm up for a few minutes . Again,
if you get smoke or smells, unplug
immediately .
Connect your multimeter's negative
lead to ground .
Set the multimeter to 5V DC and
check eyelet 32, which should read
around 1 .3V .
Set the multimeter to 200V DC and
check eyelet 39, it should read around
130V .
If all of these voltages come within
approximately 10% of their expected
values, unplug the unit .
If the reading at eyelet 39 shows
no voltage or low voltage, follow
this test: Unplug the unit, drain the
filter caps with the snuffer stick
(instructions on page 6), set your
meter to read continuity, and make
sure you have properly installed the
flying jumper from eyelet H of the
filter cap board to eyelet 23 by testing
for continuity between eyelet H of the
filter cap board and eyelet 23 .
If all of these voltages come within
approximately 10% of their expected
values, unplug the unit.
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STEP 87
Test the 6V6 power tube
With the unit unplugged, install the
6V6 power tube . Plug the footswitch
into the back of the reverb unit .
Plug a guitar cable into the reverb
unit's output jack . Plug the other end
into your amp's input jack . Turn your
amp on .
Perform these next tests with your
amp turned away from you . If it starts
to squeal, this helps protect your ears .
Plug the reverb unit in . After a few
moments you should hear a low hum .
If the hum becomes very loud, unplug
the unit and your amp immediately
and review your connections .
After the unit has warmed up for a
few minutes attach your multimeter's
negative lead to ground . Set your
multimeter to read 5V DC and test for
voltage at eyelet 36 . This should read
around 1 .3V .
Set your multimeter to read 500V DC
and test for voltage at pin 4 of socket
V6 . This should read around 285V .
If the readings are correct, plug in a
guitar and play at low volume . If the
reverb unit behaves as it should, keep
increasing the dwell and mix and test
the tone control . The reverb should
saturate as you increase the dwell .
If the reverb isn't working, switch the
cables in the reverb in and out jacks .
If that doesn't remedy the issue, check
your reverb cables again for a short .
If the unit squeals or seems unstable,
use a wooden chopstick to probe for
loose connections:
from the input jacks to the board
n
from the tube sockets to the board
n
from the tube sockets to the front
n
panel controls .
It usually takes just a minor wiring
adjustment, perhaps resoldering
a loose joint, to correct this sort of
distortion .
33
STEP 88
The last step
If the unit is stable and your tests
match the voltages specified, feel free
to let it rip!
If everything seems to be operating
normally after playing for a few
minutes, go ahead and turn the unit
off . Install the cable clamp to mount
the power cord on the side wall of
the cabinet . Install the tube shields
over the nine-pin tubes, and install
the back panels .
Tube life
The life span of the power tubes is
affected by how hard you drive the
unit . If you are really driving the unit
for hours every day, expect the power
tube to have a shorter life span .
We encourage you to experiment
with different tube brands and find
the brand that is most favorable to
your ears and your wallet .
For questions and support,
StewMac is here to help!
For more than fifty years, StewMac
has supplied instrument builders and
repair shops . Our customer service
team really knows how to help if you
run into questions .
Call 800-848-2273 from 9AM–6PM
Eastern time, Monday–Friday .
Email: service@stewmac .com
Thanks for choosing this StewMac
kit, and welcome to the world of amp
building!
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