Steve
You can lift one lead of the cap in question, and then measure the resistance in the ckt with an ohmmeter.
Doug
:Andy: It sounds like your tester is seeing a parallel circuit when doing the in-circuit test. Can you tell us what radio this is, and which cap you are trying to test?
:Steve
On your CT-1 testing, you didn’t clarify as to whether you were in the tuning eye mode for testing for capacitive value / or / in the
short / leakage mode testing aspect.
Looking at the input circuitry of the CT-1 unit, you can see the green circled connection being the high Z and sensitive input of the instrument while the lower terminal being the quasi ground potential related of the two.
I might consider the unit either picking up a AC hum ground loop….. IF ….the test set had any possibility of picking up stray AC
which would be amplified and produce an eye tube indication of a fault. Otherwise considering that the test chassis is so well insulated and isolated, such that is not a consideration.
The second thought would merely be the manner in which the leads were connected to the cap left in the tested set, with its one lead out of circuit and floating. In that situation one would want the ground potential lead of the Heath going to the capacitor connection that is still connected to the chassis, while the Heaths top “sensitive” lead would be the one going to the floating lead of the capacitor being tested. If the Heath interconnects were made the other way around, with the low potential Heath lead going to the free lead of the capacitor that then leaves the SENSITIVE lead going to the lead that is connected to the bulk and mass of the chassis which is subject to stray signal pick up. Much like your finger test to an input stage of a high gain audio amplifier and the resultant “buzz” in this case it erroneously fooling the eye tube.
Vot you thinks ? 
73's de Edd
It works by using a low voltage high frequency (100Khz) signal injected into the capacitor under test while in circuit. It really is made for electrolytic caps and I will tell you it works great. A friend used one about 7 years ago to fix a Sharp TV I have that was not working. I couldn't find the problem, his meter pinned 3 dead caps in seconds. I was sold, but I couldn't cough up the $150 needed for an ESR meter. The one above is available built for $129, or kit for $79. It already helped to fix the same TV, as well as a computer power supply with bad electrolytics.
Hope this helps.
:It works by using a low voltage high frequency (100Khz) signal injected into the capacitor under test while in circuit. It really is made for electrolytic caps and I will tell you it works great. A friend used one about 7 years ago to fix a Sharp TV I have that was not working. I couldn't find the problem, his meter pinned 3 dead caps in seconds. I was sold, but I couldn't cough up the $150 needed for an ESR meter. The one above is available built for $129, or kit for $79. It already helped to fix the same TV, as well as a computer power supply with bad electrolytics.
:
:Hope this helps.
The problem with capacitors is that they are among the most difficult components to test. I worked for a major capacitor manufacturer for years. I helped to build all of our in house test equipment. Capacitance is only ONE parameter of a good cap. There is also leakage, DWV (dialectric withstanding voltage). For electrolytics, the same factors but also ESR, Dissapation Factor and Dialectric absorbtion. Throw in operating frequencies and temperature and you have a real beast to contend with if you are to really prove that a capacitor is "good". I've seen many capacitors of all types check good in every way and then fail to work in its specific application. For, us though as antique radio collectors, we deal with generally low freq. applications. Capacitance and leakage are the dominant factors for testing most coupling and by-pass capacitors. For electrolytics, cap, leakage and an ocasional high ESR are things to test for. For those with ESR meters remember that they can check caps that seem good but have low cap values or other problems. What I'm basically saying is: when testing a capacitor, don't rely solely on ONE test. Test as many parameters as you can.
::It works by using a low voltage high frequency (100Khz) signal injected into the capacitor under test while in circuit. It really is made for electrolytic caps and I will tell you it works great. A friend used one about 7 years ago to fix a Sharp TV I have that was not working. I couldn't find the problem, his meter pinned 3 dead caps in seconds. I was sold, but I couldn't cough up the $150 needed for an ESR meter. The one above is available built for $129, or kit for $79. It already helped to fix the same TV, as well as a computer power supply with bad electrolytics.
::
::Hope this helps.
:
:
:The problem with capacitors is that they are among the most difficult components to test. I worked for a major capacitor manufacturer for years. I helped to build all of our in house test equipment. Capacitance is only ONE parameter of a good cap. There is also leakage, DWV (dialectric withstanding voltage). For electrolytics, the same factors but also ESR, Dissapation Factor and Dialectric absorbtion. Throw in operating frequencies and temperature and you have a real beast to contend with if you are to really prove that a capacitor is "good". I've seen many capacitors of all types check good in every way and then fail to work in its specific application. For, us though as antique radio collectors, we deal with generally low freq. applications. Capacitance and leakage are the dominant factors for testing most coupling and by-pass capacitors. For electrolytics, cap, leakage and an ocasional high ESR are things to test for. For those with ESR meters remember that they can check caps that seem good but have low cap values or other problems. What I'm basically saying is: when testing a capacitor, don't rely solely on ONE test. Test as many parameters as you can.
Thanks everyone for your comments and suggestions.
The CT-1 Capacitor Checker was designed to disclose open and shorted caps without removing them from the circuit. (so says the manual!!) Radio should be unplugged when testing, of course.
The cap I was testing was a 0.1mfd 630v in a Zenith 6G00YZ1 Universal. The third picture shows it under test. This cap was connected to pin 4 of the 1LN5 tube and pin 8 of the 1LA6 tube. Unfortunately I can't find a schematic of this particular Zenith.
The first picture shows testing for a short and the CT-1 is in the "check" position indicating that the eye should be open. As you can see, the green eye is in fact open. The second picture shows the knob being turn to the "test" position and if there is a short the eye will be open or if the eye is closed it is OK. The green eye in this case remained open thus indicating a short. If I disconnect one leg of the cap and put it under test then it reads OK.
I assumed that most of us were using a type of cap tester but reading other comments it seems that most of us are using an ohmeter. It seems like a lot of work to disconnect the one leg from every cap and then have to resolder every one if it tests ok. I guess this is why I bought the in-line tester. Maybe I'll use the ohmeter!!!
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