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These waveforms were made on a calibrated scope type 524àD
Tektronix,
if a calibrated scope is not available an ordinary
scope may be calibrated approximately by the following method:
Peak- to- peak waveforms are always 2.8 times the HMS value of
a sine wave.
The hot scope lead can be connected to
2
hot fila-
ment wire which should have an kC voltage present of about 6.3
volts AC.
The peak-loppeak value would then be 17 or 18 volts.
The scope can then be calibrated accordingly by setting a refer-
ence point on the scope screen.
The two most important waveforms to check are those at TP102 and
TP105.
With pin 7 of V103 disconnected, the waveform at TP102
should be a good saw-tooth with an amplitude of 25 to 30 volts
peak- to- peak.
The leading edge should be linear with no round-
ing off.
When pin 7 of V103 is connected and the bias properly
set the waveform will be cut approximately in the middle horiz-
ontally.
With V106 removed the waveform at TP105 should be a good saw-
tooth with an amplitude of about 25 to 30 volts peak-to- peak.
The leading edge should be linear with no rounding off.
When
V106 is inserted and the bias properly set the waveform will be
cut approximately in the middle horizontally.
IMPROPZR FREQUENCY RESPONSE
If the frequency response is not correct,
the audio section
should again be checked for proper response.
The frequency re-
sponse as noted at TP120 should be approximately the desired
overall frequency response.
It usually will be 2 DB or so high
at both extremes of the audio spectrum.
Should the frequency response noted at TP120
.
nrove to be 0.K.,
but overall frequency response be down at 15,000 cycles,
it will
usually be caused by too narrow a bandwidth or mis - tuning of
some of the low frequency multiplier stages, L101 thru L107.
L101 thru L103 are most apt to cause this difficulty.
Improper
tuning of the modulation and frequency monitor can also affect
apparent frequency response.
A change in the components associated with the modulator stages
can cause poor low frequency response,
this ié especially true
of C112,
C121, R114, R113,
R115, R126 and R127.
WILL Nor .10DULATE AT :iLL
This condition will probably resolve down to a dead audio stage.
-24-
M6095 Exciter
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