RCA VoltOhmyst WV-77C, Технические характеристики, Управление, Применение, Техническое обслуживание

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ACCESSORIES
A v ailahle on Se p arate Order
The W G-30 1 A C r ys tal -D i ode P r o b e co n s i s t s of
a
germa n ium r ec tifi e r and an R C n etwor k hous ed i n a
probe wh ic h s l i ps onto th e \ VG- 29 9B P r obe and
Ca bl e . T h e max i m u m v olta ge ra tin g of t h e ins tru m e nt
w ith th e WG - 3 01 A i s 20 vo l ts n ns , i n t h e pr ese n ce of d e
voltag es up t o 250 v olt s. T h e fr e qu e n cy ra ng e i s 5 0 Kc
to 250 Me. V olt age read in g s are made o n the d e sc ale s
in terms of TI ns v olt s for s in e wa ves.
_ Th e W G -289 H i g h- V olta ge Probe in c ombinati o n
with
a
mult i p l i e r r es i s tor W G -206 ex ten d s the d e rating
o f t he
\'\iV - fie
t o a m a xim u m o f 5 0 , 00 0 v olL s fo r usc
in h i gh-impedan c e c ir c uit s. D C s c a l es are multi pl ied
by a f act o r of 1 0 0, prov i di ng 4 f ull - sc ale po s i t ion s of
300, 1 200 , 6 0 00 , and 30, 0 00 v olt s. The 12 00 - v o lt ra n g e
i s also useful u p t o th e m a x im u m r a ti n g of 50 , 000 volts
on t he probe. Wh en th e p r ob e is u se d , the to t a l input
r e s i stance i s i n c r e as e d t o 110 0 me g o hm s, a v alu a bl e
f ea t u re f o r m ak in g me a s ur emen t i n photo tu b e c ircui ts ,
TV h i g h- voltage p o w e r su pp l i es , and o lh e r h i g h- i m -
p e d a nc e circu i ts ha v in g inh e rentl y p oor r e gul ati on .
Figure 4. A cc e ssory high-voltage probe and multip li er r e s istor for
us e wi th th e W V-77C
Special Applications
T h e
\' \l V- r7 C
is general l y u sefu l i n th e ma i nt e nance
a n d ser v icing of ac, d c , af, an d hi g h-fr e quen cy equip-
me n t . ""hen u s ed wit h t h e ' ''G - 30 1 A C r y stal - Di od e
Probe, it c a n he use d to measure rf v o ltages a t f re -
q u e n c ie s bet wee n 5 0 K c and 2 5 0 Mc . The special appli -
cat io ns discuss e d below w ill serve to illust r a te t h e w ide
fie l d of u sef u lness of t he WV - 77C.
Osci lla t o r G r id -B ias l\ie a surelnent. T h e ne g a-
t i ve d e v o lta g e de ve l o p ed a t t he grid of a n o s c illa t or
tu b e is al w a ys pro p o rt io n a l t o th e amplitu d e of o sc illa-
tion . The WV - 77C h as h i gh i npu t i mpeda n ce a n d can
b e u s ed to me asure this bia s vo lt age _ C omp ara t ive r e a d-
ings sho u l d b e taken on eac h b and o f a multi - b an d
rece iv e r. The g a n ged tunin g capac itor s hould be r o -
tated throu g h ea ch b and while t he bias i s me a s ur e d .
A G e / AVe Volta g e Mca8ureme n t s . S i nce the
\ VV·7 7C ha s a h i g h in p ut res i s t ance, i t ca n b e u sed
t o
m eas ure avc o r agc v o l ta ge at th e di od e lo a d r es i sto r,
a l on g th e bi as bu s es , or at th e g r i ds of the tub es.
Outp u t In di c ati o n . T h e WV - 7 7 C i s a ve r y u se f u l
out p u t i n di c at or f o r al ig n m en t of ra d i o and telev i s i o n
re c e i ve r s . The \'\ iC - 29 9B pr obe is u s uall y c onnec t ed
t o th e l o a d r esis t o r o f t h e second d e t ec t o r in AM an d
TV r eceiv er s . I n an FM rec e i ver , th e prob e i s con -
nect e d t o th e li m i t e r l oad res i sto r. Th e zer o - ce nter
f e ature of the WV - 77C is p ar t icu l a rl y u sefu l in a li g n-
m ent o f FM di sc r im i nators.
Bias - Cell Voltage Mea s u r eme n ts. B ias - c ell v olt -
ag e s ca n be a ccur a t e l y me a s u re d w ith the W V - 77C.
Detection of Gassy Tubes . A n o c cas i o n al ga s s y
t ub e m a y b e e n c o u n te r ed in e l ec troni c eq u i p me nt . The
p r e se n ce of g a s in a n o u tput tu b e o r a vc - co ntrolled tube
ca n l e a d to v ariou s c ir c uit d i s tur ba n ces. M e asur e me n t
of th e gr i d bia s in a n RC-co upl ed ci r c uit s hows the
pr ese n ce of a g a ssy t ub e as a n a bnormall y negati ve o r
po siti ve valu e of bias . T h e sa m e s ym ptom can also be
c au se d b y a l ea k y cou pli ng c apacitor .
In su lati o n - Resistance M e asu r ements. Curren t
l e a ka ge t hr o u g h th e i ns ulatin g m aterial of c apacitor s,
c oil s , tra nsf orm e r s , cable s, and other compone n ts , can
be meas ur e d w i th t h e WV - 77C i n term s o f r es i s t a nce.
V alues o f le a ka ge re s i s ta nce abo ve 1 000 megohms can
b e meas ur e d with th e ci r c u i t s h o wn i n F ig . 2_
DBM Me a surements. Th e c hart s hown in F ig. 1
can be u se d to de t e rmin e dbm v alues co rrespondi n g to
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