T EVIS i - AmericanRadioHistory.Com

B2
IT'S TERRIFIC!
Fig. 3. Circuit to illustrate heory of
operation. See text for full exl lanation.
± 20%r) is provided for zeroing over
the range of battery volta> e. At this
point it is well to note that the large
variation in current drawl from the
battery on different range will tend
to make the effective battery voltage
vary from approximately 1 55 volts on
the highest range to about 1.40 volts
on the lowest range. This should be
considered when deciding of the values
for these resistors. It w 1 be noted
that in the writer's parts list R, is
given a value of 2500 oh ns whereas
2000 might have been expected from
the values shown for R., R., and R,0.
This was found necessary for correct
zeroing on the high range, due to the
relatively high battery v ) ltrge when
only 0.5 ma. current is being drawn.
In use, the desired range is selected,
and the zero adjusted so that full scale
deflection is obtained wi h the leads
open. The leads are then connected to
the unknown resistance to be measured,
the push- button pressed, and the
resistance read (scale reading x appropriate
multiplier).
In order that the constructor may
adapt this circuit to any available
meter, the essential theory follows,
where Fig. 3 indicates the essential
components for any one range.
Now let:
X - res. to be meas'cred.
S = res. of meter si unt.
M = res. of meter.
R =total res. of zero -adjust
branch.
R= battery terminal volt a g e
(operating).
For decade ranges, the s alues of S for
each range will be R,, l't, R. and will
be given as R.= M /9; R: = M/99;
R. = M/999, etc.
Now let Q = paralle, resistance of
range being considered, i.e.:
MS
`e -
M + S
Let the current for full scale meter
reading with X disc,nnected (obtained
by adjusting R, i.e., by zeroing)
be L.
Let the corresponding( current obtained
with X connecte3 be L. Then it
can be shown that:
RQ
(1 -A) (R Q)
where:
X = -A
. (1)
to
The highest range is determined for
no shunt, i.e., for S = infinity and Q
April, 1953
7
MODEL
470
-
PUSH -PULINCH L
BOOSTED VERT. SENSITIVITY:
10 my rms in.
EXTENDED FLAT FREQ. RE-
SPONSE:10 cps -1 MC( 2 db).
3-STEP FREQ.-COMPENSATED
ATTENUATOR; cathode follower
input.
INTERNAL VOLTAGE CALI-
BRATOR; dir. -cal. screen.
SCOPE
EXTENDED SWEEP RANGE:
15 cps -100 kc.
INT. POS. OR NEG., EXT.
1, LINE SYNC.
ON FRONT PANEL: sawtooth,
60 cps outputs; intensity
mod. t ext. sync inputs.
VAR. PHASING of int.
60 cps sweep.
DIRECT CONNECTION
TO CRT PLATES.
ederated urrhase.
66 Dey Street New York 7, N. Y. Dlgby 93050
AC -DC MUSIC AMPLIFIER
Volume and tone control.
1.5 w. output.
See your jobber.
MICHEL MFG. CO.
227 N. Water St.
Milwaukee 2, Wie.
ORDER Now/
For lull specifications
on Model 470 end the
complete FICO line,
write for latest catalog.
Newark, N. l., 114 Hudson St.,
Allentown, Pa.. 1115 Hamiltcn St.,
Easton, Pa., 925 Northamptoi St.,
Los Angeles 15. Cal., 911 So. Grand Ave.,
CALIBRATED
CAPACITOR
Enables you to measure:
t "apart...
Indurtanee old Q.
I,istrlbuted Capacity.
Inductance.
r i W1c$5.65 rite for information.
P. E. HAWKINS CO.
.n.a y6 St. M.
3208 City IL M.
PAY LESS FOR TUBES
INDIVIDUALLY BOXED FULLY TESTED EACH TUBE GUARANTEED FOR SIX MONTHS
Type Price Type Price
183GT
S 89 SASS
S .50
1145GT
.45 6AT6
IL4
38
.57 6AU6
.43
1N5GT
.57 6AV6
.35
1RS
.56 6546
.96
155
.47 6BA6
.45
174
.56 BBC!
.53
ITSGT
.71 68115GT .89
1X2
.67 88E8
.47
305GT
.65 60F5
.60
354
.55 613516
1.34
3V4
.56 GBH6
.57
5U40
.43 6818
5V4G
.48
.73 6BK7
1.10
5Y3G
.34 6BL7
5Y3GT
.30
.53
68036
6ÁB4
,46
,p
5557
6AF4 140
1.10
6ÁG5
.54
6BZ7
1.10
6ÁK5
.95 6C4
.34
6AK6
.63 6CB6
63
6AL5
.40 6CD6
1.85
6ÁN4
1.30 6F6CT
.45
6AQ5
.46 8H6GT
.49
BARB
.42 615GT
.40
GARS
.38 818
.62
Motorola ballast Tube
n tube
Type
6K6GT
6L6G
6L6GA
654
65A7GT
65170T
6SK7GT
6SL7CT
6SN7GT
6SQ7GT
678
6118
6VOGT
6W4GT
6W6GT
6 %4
6X SGT
6116G
7N7
12AT6
32ÁT7
12ÁU6
12ÁU7
125V6
12AV7
12AX7
Price Type Price
S .41 12AZ7 S .70
.80 120A6 .45
.80 1213E6 .47
.46 12BH7 .63
.52 12827 .75
.47 125A7GT .52
.50 12SK7GT .50
.62 125L7GT .61
.54 1251.17011 .54
.42 125076T .44
.78 1813G6 1.39
.85 19C8 .94
.46 1878 .79
.45 251306 .89
.57 2SL6GT .48
.34 25Z6GT .42
.33 35AS .48
.59 35B5 .47
.52 35C5 .47
.38 35L6GT .47
.86 35W4 .31
.43 5S25GT .30
.55 5005 .47
.38 8005
.47
.80 6076
.61 11723 .39
.30 11726 .68
ra Pertomence- proven.
prices S.P.A. 25% de N.Y.C. I
accompany
remittance
all owes Balance
,
C.o.n, All
made ß,1h oder. you c1
ro deduct 20. s. $1.00 nahm q
ordere
charm.
under e510.00. subject to nPr,or sue.
PHILLIPS TUBE COMPANY
2281 Noetann
BROOKLYN 34. Y.
CLOrrrUalr 3-e010-1-2
147