Heathkit SB-1000 - Operation Guide

Heathkit
Page 63
TUNE-UP
The current and voltage figures given in this section
are approximate. Actual indications will vary at
each installation with such factors as line voltage,
exciter drive, and load impedance.
The following procedure for tuning the Amplifier
should take only a few seconds after you go through
it a few times. Note the LOAD control position so
you can preset it the next time you use a particular
band.
35
3.8
8b8s
CW PROCEDURE
Make sure you have the Amplifier connected as
described in the "Installation" section. IMPOR-
TANT: Before you proceed, make sure you have a
dummy load (such as the Heathkit Cantenna) or an
appropriate antenna connected to the Amplifier out-
put.
1. Preset the Amplifier controls as follows:
PWR/OFF ————— Off
OPR/STBY STBY
MULTIMETER -—— High Voltage
2. Plug the line cord into a proper AC outlet.
3. Set the PWR/OFF switch to PWR. The meter
lamps should light and the fan should run. The
0 to 3500V scale on the multimeter should
indicate approximately 3400 volts.
4. While the Amplifier is still in standby, tune
the exciter into the normal 50ohm load
according to the manufacturer's instructions.
Then, after you have the exciter properly
tuned, turn the exciter drive all the way down.
FREQUENCY BAND PLATE
(in MHz) CONTROL
1.85 160 160
NOTE: If tune-up on the higher frequency bands is
broad and the LOAD control is at minimum capaci-
tance, you may be able to improve the tune-up by
slightly expanding the section of tank coil L7 that is
between tap #3 and point CP (refer back to Pictorial 6-
13).
For your convenience, the following chart shows
typical settings:
LOAD CONTROL
(typical)
5. Turn the BAND switch to the same band as the
exciter. Then preset the PLATE and LOAD
controls to the positions indicated in the above
chart for the band you have selected.
6. With the exciter drive still at zero, set the
MULTIMETER switch to PLATE CURRENT.
The 0 to 700 mA scale should indicate zero.
Now set the OPR/STBY switch to OPR.
7. Key the exciter (with no drive) and observe the
plate current on the 0 to 700 mA scale. The plate
current should now indicate 50 to 80 mA.
8. Apply only enough drive to obtain 50 mA of
grid current and no more than 200 mA of plate
current. Now tune the PLATE control for maxi-
mum grid current. Unkey the exciter. NOTE: It
is normal for the plate current to dip (be
reduced) when you have maximum grid current.
If the grid current goes over 100 mA, immedi-
ately reduce the drive.
9. Set the MULTIMETER switch to POWER
OUTPUT and observe the 0 to 2000 peak RF
watts meter scale. Again key the exciter and