Heathkit CT-1 problem ?

The manual I have for the CT-1 shows a 10 pf capacitor across the oscillator coil, however, it's not in the parts list either. The oscillator coil must have come from the factory assembled with a tuning capacitor that made the circuit oscillate at the correct frequency. Do you have a complete manual that gives the circuit theory of operation? That section describes both open and short checks as well as normal operation. If not, I can send you a PDF of the manual.

Cheers!!!

Henry, I just opened mine and it has a 10pF NPO ceramic across the end of the coil opposite the green dot [the left end looking from the rear]. The frequency of the oscillation in not as critical as it operating over the range of loads, so I should try 10pF and see how it works with a variety of capacitor values under test. If it craps out at either end of the load range, try 5, 15 or 20pF and see how it goes.

Neil S.

The CT-1 uses an oscillator tuned to approximately 19 MHz for the open test. It does not matter if it is 21 MHz or 17 MHz, and there will be no difference between a 5 pf or a 10 pf or no pf across the coil.

If no one got offended, I would say that you are barking up the wrong tree. But, I do not want to hurt anyone's feelings, so I will not say that. My dog would not get her feelings hurt if I talked like that to her, but people do.

The problem is elsewhere.

One of the problems, when you pick up something that does not work, is assuming that it ever worked. Sometimes kits were assembled, and did not work, then put on the shelf where they languished for decades.

Check the wiring and check to see if the oscillator is oscillating. Sometimes switch contacts are wired incorectly. Sometimes switches are improperly cleaned then fail Sometimes resistors fail.

In the past, we check the paper and electrolytic caps. Now, we may need to check the mica caps.

Colin K7FM

good statement - don't assume it ever worked - at one time I made my spare change fixing kits that the purchasers couldn't assemble correctly.

ROFL.

With my Heathkit assemblies, it's usually worth to look at those caps most difficult to get at :-).

Regards, H.

I checked mine and the schematic does not show any cap across the 'large' coil, nor is there one. You might check the cathode for oscillation activity since virtually any capacitance across the secondary will kill the oscillation [even a 'scope probe]. There is not a whole lot in there to go wrong, so you might check the eye tube triode for emission; if it is weak that could be a problem, or if it has been inactive for a long time. Mine has not been used since I refurbished it 10 or so years ago, and it worked immediately I turned it on and the tube warmed up.

Neil S.