308J
OFFICIAL RADIO SERVICE MANUAL
cuppleourni No. 5
PHILCO RADIO & TELEVISION
CORP.
PHILCO
Service Bulletin
P.."
No. 136
Adjustment of Shadow Tuning
Philco shadow tuning is one of the greatest aides to correct tuning ever developed so it is important
that this device be properly adjusted on each set before being placed in operation. There are no adjust-
ments inside the shadow box, but there are a few simple adjustments of the position of the box
and
the position of the pilot lamp.
INSTALLATION
The shadow tuning box is purposely moved back away from the bezel during shipment so as to
avoid breakage. When the set is placed in operation, and after the chassis mounting bolts have been
loosened, the two mounting screws at each side of the shadow box should be loosened by means of a
short screwdriver, and the box moved forward to the bezel. The position of the box can be adjusted
so that the shadow is centered with respect to the bezel opening.
POSITION ADJUSTMENTS
In some cases, it may be found that the position or the intensity of the shadow on the screen is
not entirely satisfactory because of slight changes during shipment.
The necessary re -adjustments can
be made in the manner outlined below, first turning on the radio and removing the type 80 tube.
1.
Shadow too faint. Move and focus lamp by bending the bracket slightly to obtain a sharp
shadow of the smallest possible width exactly in the center of the screen.
2.
Shadow not centered on screen. Move and focus lamp as described above.
3.
Shadow not sharp on one side.
Pry off the lamp reflector and adjust the lamp position by
turning lamp and socket in a clockwise direction until the filament supports are parallel to
the back
of the shadow tuning box. Ordinary pilot lamps with inverted U shaped filament will not be satisfactory
since they do not produce a concentrated light and a sharply defined shadow.
The new Philco pilot
lamps have a relatively straight filament which gives better light concentration.
It may be necessary
to make a further adjustment by bending the
bracket as described in 1. above.
4.
No light on screen.
Adjust reflector on pilot lamp.
5.
White light between screen and bezel opening.
Loosen shadow tuning box mounting
screws, and move box forward against
back of bezel.
Center shadow properly with respect to bezel
opening.
Replace the 80 tube after completing the above adjustments.
RADIO ADJUSTMENTS
After the above adjustments have been made, the shadow tuning box may be checked for operation
by tuning in a number of stations. The following suggestions are offered in case of
difficulties:
1.
No change in shadow width when tuning in weak signal. Change first detector and first
I. F. tubes in Model 15 and R. F. and I. F. tubes in Models 91 and 23.
2.
Insufficient change in shadow width on all stations. Look for faulty aerial connection
or too small aerial.
3.
Shadow remains at minimum width while dial is turned several divisions. Compen-
sating condensers our of adjustment, causing set to be broad in tuning; station
signal extremely broad
DO NOT ATTEMPT TO MAKE ANY ADJUSTMENTS INSIDE THE SHADOW BOX.
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