Heathkit SG-8 Assembly And Operation Manual page 8

(2) . Connect an output indicator to the receiver. This may be an AC voltmeter connected di-
, rectly across the loucspeaker voice coil; however, a VITVM connected tomeasure AVCvol-
tage is by far the most desirable method.
(3) Short ou the local oscillator tuning circuit temporarily. The simplest way to accomplish
this is merely by clipping a short piece of wire across the rotor and stator plates of the
oscillator section of the tuning condenser. Set the receiver dial to the low frequency end,
somewhere near 550 KC.
(4) Connect the signal generator to the antenna terminals of the receiver or if the receiver
employs a loopantenna or rod antenna, couple the output of the generator to the antenna sys-
tem through a one or two turn loop of wire around the antenna. In cases where an RF stage
is used ahead of the mixer, connect the signal generator to the injection grid of the mixer
stage. Set the signal generator to the IF value 0: th? set. (455 KC is generally the accepted
standard.) Use a modulated signal if an AC voltmeter is employed as an output indicator.
An unmodulated signal is used provided the AVC voltage is used as an output indication.
(5) Using the lowest range of the output indicator, increase the output of the signal generator
until a reading can just be obtained.
(6) Adjust the IF transformers for maximum reading on the output indicator. Reduce the sig-
nal generator output as necessary to keep a low reading on the output indicator. Repeat the
adjustments at least once to correct for any interaction between primary and secondary
windings on the individual transformers. Interaction is most likely to occur in sets where
adjustment is by means of iron-core slugs rather than trimmer condensers.
(7) Next, remove the short across the local oscillator and tune the receiver to its highest fre-
quency settiny: (somewhere around 1600 KC). Set the signalgen herator to the same frequency
and adjust the os: illator trimmer for maximum out >ut.
A
(8) Now tune the rec-iver and signal generator to 1400 KCand adjust the RF trimmer for max-
imum outnut
~ imum output
(9) Turn -he signal generator to 600 KC and tune the receiver to the low frequency end of the
dial. Vow "rock" the receiver tuning condenser while at the same time adjusting the trim-
mer condenser formaximum cutput. In sets using especially shaped plates inthe oscillator
,section of the tuning condenser, generally no trimmer condenser will be found. Also, in
some sets, the kw frequency oscillator adjustment will be through means of an iron-core
slug in the oscilletoér coil rather than a trimmer condenser.
(10) Steps 7, 8 and 9 should be repeated if it was found necessary to readjust the trimmer con-
denser (or iron-c re slug) as directed in Step 9.
The alignment procedi re for muiti-band AM superheterodyne receivers is essentially the same
as outlined above fora single-band set. First the IF stages are aligned using the same technique
as given in Steps 1 through 6. Next, each RF band is aligned separately, starting with the high-
est freque: cy band an1 working towards the lowest. The technique given may be used but with
corresponc ing frequercy Settings for each band.
If the oscillator and F F trimmer condensers for the different bands are not well identified, a
simple teclinique may be employed to locate the proper adjustment screws. Turn the receiver
band switch to the hig] est frequency band and tune ina signal, using a short-wave station or a
signal from the RF generator.
Using an insulatedalignment tool, try compressing the different
oscillator trimmers until one is found that changes the tuning of the signal. Do not compress
the oscillator trirnmer condensers by turning the adjustment screws, just press the leaves of
the condenser together temporarily. This method will identify the trimmers for each band with-
out drastically changii g their original setting. After identifying the oscillator trimmer for the
band in this manner, -'epeat the technique to identify the RF trimmer. Turn to the next band
and reveat the method being careful not to touch the trimmers already identified.