TXC-1 through TT-1E/TXC-1. The voltage
range of the 1B46 or the R1160A is 79 to 85 volts,
that of the 5651 is 82 to 92 volts. Both must
When making a replacement, measure the voltage
across the lamp. If the voltage is not within the
proper range, try another lamp.
Caution: Do not remove regulator lamp V25
or tube V7 with the power turned on. If this is
done, the RB+ voltage will rise to approximately
350 volts and possibly damage some of the com-
ponents.
b. Tube V7 is a critical factor in the voltage
control. There are times when it may be easier
to select a tube for V7 than to select a voltage
regulator lamp to produce the desired output
voltage.
c. Oscillations develop in the regulator circuit
at low line voltages; that is, at the point where the
voltage regulator lamp drops out of control.
Oscillations sometimes are aggravated by a feed-
back condition. Feedback can be remedied by
separating the connections to the screen grid of
TT-1D/TXC-1, TT-1E/TXC-1, and TT-1F/TXC-1.
tube V7 from the connections to the plate and grid
of other tubes in the regulator circuit. Replace-
ment of V25 may be necessary in some cases.
If the DB METER readings are not correct,
first try a new 7N7 tube in stage V13. If the
results still are not satisfactory, replace the original
tube. Check the resistance of R61, R62, R68,
former used in earlier equipment was Kenyon
and R69. If the value of these resistors is found
type T246. This transformer may be used as a
to be correct within 10 percent, select the value
replacement, but the filament winding feeding the
for R70 to get the required reading. The value
transceiver unit will be overloaded. The original
of R71 should be as specified. The DB METER
T246 has two 6.3-volt, 3-ampere filament wind-
used with Facsimile Transceivers TT1D/TXC-1
ings. The modified transformers have one 6.5-
and TT-1E/TXC-1 is hermetically sealed. To
volt, 1.75-ampere filament winding, and one
zero-adjust the meter, use a 20-watt soldering
6.5-volt, 6.25-ampere filament winding. The fila-
iron having a small chisel-shaped tip. Insert the
ment windings of a replacement transformer may
heated tinned iron into the slot of the zero cor-
not be phased the same as the original. If the
rector. When the solder so softens, rotate as
phasing is not correct, the motor start voltage
necessary for correct zero setting. Remove the
across terminals 5 and 8 of the Jones plug will be
soldering iron and the seal will solidify. The
about 3 volts instead of the required 10. To
instrument is then ready for use. This procedure
phase the windings, remove the jumper wire from
will be used in an emergency only. In Facsimile
the 1.75-ampere winding. Connect it to the
Transceiver TT-1F/TXC-1, the zero adjust-
other end of the same winding. For example, if
ment of the DB METER is made with a screw-
the jumper is on the terminal with the green wire,
driver.
move it to the terminal with the brown and yellow
wires.
a. Regulator lamp V25 is designated as type
b. Chokes T12 and T13. These chokes may be
R1160A or 1B46 in unmodified Facsimile Trans-
replaced with close equivalents that fit in the
ceivers TT-1/TXC-1 and TT1A/TXC-1, and a
space available.
type 5651 in the modified unlettered and -A
c. Capacitors C12, C13, and C14. These capaci-
models and in Facsimile Transceivers TT-1B/
tors have a rating of 1,000 volts. In an emergency,
