Specifications

Changes in force: C#2 C#4, C#5 and C#6
TM 11-6625-496-45
C6
Change
No. 6
HEADQUARTERS
DEPARTMENT OF THE ARMY
Washington, DC, 12 March 1980
General Support and Depot Maintenance Manual
Including Repair Parts and Special Tools Lists
TEST SETS, RADIO AN/VRM-1 AND AN/VRM-1A
(NSN 6625-00-892-5542)
TM 11-6625-496-45, 3 July 1962, is changed as follows:
The title of the manual is changed to read as shown above.
Page 2. paragraph 1, subparagraph c is supersed-
ed as follows:
c. Report of errors, omissions, and recommenda-
tions for improving this publication by the in-
dividual user is encouraged. Reports should be sub-
mitted on DA Form 2028 (Recommended Changes
to Publications and Blank Forms) and fowarded
direct to Commander, US Army (communications
and Electronics Material Readiness Command,
ATTN: DRSEL-ME-MQ. Fort Monmouth, NJ
07703.
Paragraph ld, subparagraph (5) is added after
subparagraph (4).
Add the following sub-
paragraphs:
(5) The TS-1777A/VRC displayed a problem of
long warmup voltage data drift. When the CO/NO-
CO test voltage levels are set at the time the set is
first turned on, it seeks a new set of test trigger
voltage levels after approximately 30 minutes. This
condition has been alleviated by the fol1owing
changes, The changes have been incorporated in the
TS-1777A/VRC starting with serial number 602 and
higher under Contract No. DAAB05-73-C-1632
(1973) and succeeding contracts.
(a) The thermal resistance of diode CR7902
and resistor R7901 (figs. 14 and 54) is reduced by
the application of a silicon heat sink compound
(Dow Corning No. 340) between the mating sur-
faces.
(b) Diode CR7901 (figs. 14 and 54), type
1N645, is rated at 400 milliamperes (ma) maximum
current. Actual current measurements arc in excess
of 400 ma when tested at 28.6 volts dc. Therefore,
CR7901 is now type 1N4383 (NSN 5961-00-765-
6578) which is a l-ampere device. This will result in
a reduced statbilization period.
(c) Resistor R790S (figs. 17 and 55) has been
changed from 475 ohms (fig. 39.1) to 402 ohms
(NSN 5805-00-818-5548) (fig 39.2) This allows the
midpoint trigger leve1 for selector switch positions 9
and 14 to be set closer to the median value for trig-
gering. This action provides a more optimized
operating point. Switch position 14 must be set near
the lower limit to maintain switch position 9 value
below the operating limit.
(d) The TS-1777A/VRC exhibited problems
in sensitivity
caused by lack of adjustment
capabilities for positions 2 and 19 of the selector
switch. Fixed resistors R7902 (position 2) and R7919
(position 19) (fig. 11). respectively. have been
replaced with variable resistor R7902 in series with
fixed-film resistor R7923 and variable resistor
R7919 in series with fixed-film resistor R7922 (fig.
11.1). Resistors
R7922 and R7923 prevent
overheating of transistors Q7802, Q7803, and
associated components if the variable resistors arc
set for minimum resistance.
The minimum
resistance setting of R7902 and R7919 results in the
full input signal level of 20 volts applied to the base
of Q7802, which is in the full input signal level of 20
volts applied to the base of Q7802, which is in excess
of the normal trigger voltage of 2.6 volts. The resul -