B&K 1076, Инструкция по эксплуатации

Страница: 33 / 64

•
Make careful note where the yoke wires connect in the circuit.
Also keep the yoke disconnected while the remaining tests are being
made.
Next the width coil is tested. To do this, it is disconnected com­
pletely 'from the circuit. Note the effect upon the boost indicator
and hi voltage lights. If the width coil is defective, its removal from
the circuit will bring back the high voltage. Under these conditions,
both the B+ boost indicator and hi voltage indicator will light up.
If the width coil is in series with the yoke in a particular circuit,
remove the width coil at the same time the yoke is being removed.
If the high voltage comes back again, one of these components is at
fault. Reconnect the yoke first, using a connecting lead in place of
the width coil. If the high voltage reappears, the width coil is the
defective unit. This conclusion can be checked out by testing the
yoke with the Shorted Turns and Leakage Test of the TV Analyst.
It is common practice to tap off pulses from various points on the
secondary of the horizontal output transformer for use in the hori­
zontal AFC and in keyed A.G.C. circuits. It may very well be that
a defect exists in one of these auxiliary circuits which is having an
adverse affect on the horizontal output transformer, loading it down
and thereby preventing it from functioning normally. To determine
if this is true here, disconnect one tap at a time, each time checking
the indicators to see whether high voltage has returned. If the
boost and high voltage indicators light up after one of these leads
have been disconnected, then we know that the trouble exists in that
particular auxiliary circuit. After this, it simply becomes a matter of
tracking down the defect in the auxiliary circuit.
It may happen that even after all of the auxiliary components
have been removed from the horizontal output transformer neither
the boost or hi voltage indicators will light. This certainly points fo
a defective transformer and the TV Analyst has available the neces­
sary tests to prove that the transformer is defective. At this point
it might well be worthwhile to review the nature of defects that can
occur in a horizontal output transformer. Some of the more obvious
defects that can occur are open windings, shorts from one winding to
another, hi resistance leakage from one winding to another or from
a winding to the core of the transformer. The instrument provides a
test for these conditions. There is another fault that is less obvious.
A flyback transformer in operation is subject to both very high voltage
pulses and relatively high temperatures. This can cause breakdown
between turns in a winding resulting in one or two or more shorted
turns within the winding of the transformer. These shorted turns
represent a load on the flyback and a serious reduction in the "Q"
of the whole system. As little as one shorted turn in a winding can
result in an inoperative flyback system. These leakages and shorted
turns can also occur in the horizontal windings of the deflection yoke
and all of these tests are equally applicable to both. To test these
components they must be completely disconnected from the circuit.
To test for leakage and continuity the Calibrate control must be
turned to the Leakage-Continuity position, which is fully counter
clockwise. Connect the test leads to the Leakage Continuity test
signal jacks and check continuity of the various windings. Presence
of continuity is shown by a glow of the test . indicator bulb. When
measuring leakage between windings and from winding to core a
glow of the test indicator shows that leakage is present. The leakage
test will indicate leakage resistance from O to 10 megohms. Remove
the leads from the Leakage-Continuity test jacks.
To test a transformer for shorted turns connect the shielded cable
to the Flyback-Yoke test signal jack. Adjust the Calibrate control
31