![background image](http://html1.mh-extra.com/html/bandk/1076/1076_instruction-manual_3073936022.webp)
antenna terminals. It would be desirable not to inject the test pattern signal
into the video amplifier stages because we might do this beyond the point
where the sync signal take-off occurs. Rather than spend time looking for
this point, inject the signal as indicated above.
The next step is to apply a composite sync signal from the Television
Analyst to the grid (and chassis or B-) of V2, Fig. 8. It is important that
the proper polarity sync signal be applied and ordinarily the technician
would have to figure this out by checking through the schematic. With the
Television Analyst such checking is not necessary. Simply apply the sync
pulses from the Television Analyst to the control grid of V2. If the image
on the screen locks into sync, we know the sync signal is passing through
V2 and locking in the vertical and horizontal oscillators, and we have chosen
the proper phase of sync signal.
If the picture on the screen remains out of sync th
!='
n reverse the polarity
of the sync signal by turning the Sync Amplitude Control to the other phase.
This is the reason we do not have to know the proper sync signal polarity
before hand. The Analyst permits us to try both phases by simply rotating
the Sync Amplitude control. The picture will lock in now, if both deflection
systems are operating normally.
If the picture still remains out of sync, the sync pulses are not reaching
the vertical and horizontal sweep oscillators. In that case inject the sync
pulses at the plate of V2 and repeat the procedure. The receiver should now
sync indicating that the trouble must lie between the grid circuit and the
plate circuit of V2.
If application of the test pulses at the grid of V2 does lock the picture in,
shift the signal injection lead to the control grid of Vl. Inability to sync the
picture indicates a defect in Vl or its associated circuit. Voltage and resistance
checks should then uncover the faulty component.
The level of the test sync pulses ·may be set at any point between O and
50 volts. In most instances, a mid-setting of the sync level control will serve
satisfactorily. However, if you find that the full 50 volts peak-to-peak must
be used in order to secure adequate synchronization, chances are there is
something defective in the circuit. It may be that the pulses are not being
properly amplified or that some component has radically changed its value,
reducing the stage gain far below its normal figure. It is also well to keep
in mind that the level of the injected sync pulses should be lowered whenever
the signal lead is moved from plate to grid of a stage, or in going from the
grid of one stage to the grid of a prior stage. In short, whenever you add
more stages through which the pulse signal must pass, lower the output of
the Sync Amplitude control.
· Since the Sync Amplitude control is calibrated in volts, any level of signal
required may be injected into a receiver sync system. A schematic may indicate
that 35 volts peak-to-peak may be required to drive a particular stage. By setting
the sync level control to 35 and injecting sync at this point you may determine
if that stage will work properly with this level of signal.
A more elaborate sync separating system is shown in Fig. 9. The method
of approach is still the same, however. That is, when a symptom of poor
synchronization appears, you inject the composite sync signal from the
Television Analyst at the plate and grid of each· stage in the sync separation
system, working from the stage closest to the deflection systems back to the
stage that receives the initial video signal from the video system. The only
thing to remember is that sync polarity must be reversed when switching from
plate to grid. Failure to observe this precaution may erroneously lead you to
believe that a stage is defective.
20
Содержание 1076
Страница 2: ...Figure 1 Front Panel Controls...
Страница 61: ...TMOtl I...
Страница 62: ...Tll10 ff I...
Страница 63: ...Tll I Off I...
Страница 64: ...T Off...