INTRODUCTION
The Heathkit model CT-1 Capacitor Tester is an instrument which will disclose open or shorted
capacitors without removing them from the circuit. It is an extremely simple instrument both
to construct and operate, but yet an instrument which should give many years of good service if
the assembly instructions are followed carefully. By not trying to "out-do" the manual to come
up with an exceptionally "pretty" wiring job, you should be able to plug it in, turn it on and veil
"Hey Ma, it works'." '
An important note should be injected here: Route wiring according to the pictorial diagrams'
Due to the high frequencies encountered within the tester, lead length and placement is quite
critical, especially around the switch.
Only one tube is used, since it can be made to "double-in-brass". It functions as an oscillator
an indicator, and it is self-rectifying. '
Afive-position switch is employed, which controls the power to the instrument, selects the test
being made (i. e. ,OPEN or SHORT), and also provides acheck on the proper operation of the
»nSrVA°^°USly:. Af?r*her exPlanation of the switch position functions will be found in the
OPERATING" section of the manual.
CIRCUIT DESCRIPTION
OPEN TEST: The triode section of the electron ray indicator tube, or "Magic Eye", is employed
as aconventional Hartley oscillator, but here convention ceases. Reference to the schematic
S%2 WhTIT13Secrdary"Winding COupled t0 the oscillator c^> with the oscillator
SfJtn ?""^cycles. Now here's the catch: Coupling is "tight" enough to cause the
oscillator to quit oscillating'. In this respect it can be compared to aGrid Dip Meter. As cou!
pling is increased, the absorbtive action of the coupled circuit sucks energy out of the oscillator
coil, lowering the strength of the oscillation to the point where the oscillator quits altogether
Had enough oscillators for awhile? Then let's proceed. aiiogetner.
With no oscillation present, no bias is developed across the grid leak resultine in maximum
current low through the tube Under these conditions, the eye is open to its widest angle Whe™
acapacitor which is not open (i. e. ,good or shorted) is connected across the secondary it be
comes de-tuned sufficiently to allow the circuit to oscillate. Under tSi^SSSSe Was
is developed which limits the current flow to arelatively low value, causing th? eye t^close
In other words, if the capacitor has continuity, the eye closes. Simple, eh?
SHORT TEST: Abiasing voltage, obtained from the power transformer, is fed through acur-
rent limiting network to the grid of the tube. The test leads are connected between KrW and
Eed has^oefftr^f^^r11 ^^^^V°Uage'°pening the Cowmen fs not
shorted has no effect, unless its reactance is extremely low. However areference is nrovirferf
hanGoTaTas^ff ff'T^' ^Unl6SS the ^citorU^ct^ST^
ereniefanU tt^S^i^***~ A^™io»-«- ref-
S?^ f
SUPPLY: The P°Wer SUpply in this i^trument consists of apower transformer only
No rectifier is necessary, since the "eye" tube is self-rectifying'. When the potential on the
plate is positive in respect to the cathode, current flows. When the voltage on the plate swings
negative on the other half of the cycle, no current flows, and the tube jusf"coasts" Since AC
is used on the plate and grid, proper phasing of the transformer windings is necessary
ABOUT THE MANUAL
With the exception of the circuit description, this manual was written for adefinitely non-tech-
h^\mf
ndfmdlTldUtLT°yOU with atechnical background, it may seem rather elementary to
have to follow astep-by-step procedure such as this manual incorporates. However experience
7n Ih tyP6f°flnSiructjon methods has sh°wn the method used here to be the moW foolproof
for both amateur and professional builders. The combination of pictures, diagrams and worded
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