HOW TO USE THE TELEVISION ANALYST FOR TROUBLE
SHOOTING INTERMITTENTS
TV receivers which come into the shop for intermittent troubles can be
extremely time consuming and cause a great deal of irritation to the service
man. This is especially true when the technician cannot even isolate the sec
tion of the receiver where the source of the trouble is located.
As a typical example, let us assume a TV set has a video coupling condensor
(C4) which is opening up at random intervals for just a few seconds at a time.
The block diagram Figure 4 shows all the sections of the receiver. By
using the Television Analyst we can inject signals at various points in the
receiver and by observing the results isolate the difficulty down to a section
or single stage. Once the stage has been isolated it is just a matter of check
ing the individual components in that stage to determine the actual culprit.
SPEAKER
Figure 4--Block diagram of typical TV receiver
Many service men after narrowing an intermittent trouble down to one stage
find it economically sound to replace the suspected components one by one
until the guilty one is found. When you consider the cost of your time, it is
often wise to "waste" a few 20c capacitors to save ½ hour of your time.
In the typical example:-The customer complained that the picture and
sound went off for a few seconds every ten minutes. The service man in the
field ascertained that when this occurred the raster was still there, eliminating
the possibility of A.C. power failure, or D.C. power supply· trouble. In order
to get a raster, the low voltage supply must be working as well as .the complete
horiiontal and vertical sweep and high voltage circuits.
By looking at the block diagram it can be seen that the video and audio
signals are together in all the R.F., I.F. and Video stages. It is after the last
video amplifier that the video and audio separate. Since both video and audio
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