Rca CTC-25 overview and help

[Electronic M]

Originally Posted by ZenithNut

Thank you very much. Thats all ver helpful and i will clean it up real well. The flyback hasnt melted down or anything. Any special cleaning solutions? Mild soapy warm water?

For most cases isopropyl (rubbing) alcohol is my preferred cleaning agent. On the metal cage, the HV cables and the plastic HV rect bottom cup (with all wiring and socket removed from cup if the dirt is especially stubborn I will use glass cleaner or goofoff as the cleaner.

[ZenithNut]

Originally Posted by Electronic M

For most cases isopropyl (rubbing) alcohol is my preferred cleaning agent. On the metal cage, the HV cables and the plastic HV rect bottom cup (with all wiring and socket removed from cup if the dirt is especially stubborn I will use glass cleaner or goofoff as the cleaner.

Thank you.

Next time I power the set up I want to watch the current draw. I know the watts on it is 350. So the current draw shouldnt be over 3.2 amps or so once the sets warmed up.

I have a fluke 27/fm. How do i hook it up to watch the current draw? Do I put the negative of the meter to chassis ground and then the positive lead on one leg of the line?

[Electronic M]

Originally Posted by ZenithNut

Thank you.

Next time I power the set up I want to watch the current draw. I know the watts on it is 350. So the current draw shouldnt be over 3.2 amps or so once the sets warmed up.

I have a fluke 27/fm. How do i hook it up to watch the current draw? Do I put the negative of the meter to chassis ground and then the positive lead on one leg of the line?

Line current and horizontal output cathode current have too loose of a correlation to be used interchangeably.

The cathode current can be measured by unsoldering the ground lead from the cathode pin of the h output tube socket then connecting the meter positive current terminal to that pin and the meter negative to ground (sometimes you should put a .47uF cap parallel to the meter ). The current will be in the neighborhood of 170mA to 230mA DC. make sure your meter has a 500Ma DC scale... I'm not familiar with your meter so check it's specs/manual. Also it is preferable to use an analog darsonval movement meter to a digital meter... it is a high frequency pulsed DC current on the cathode. An analog meter will average it well and be the same instrument that Sam's and the factory used to measure that. Some DMMs may get confused by non constant DC... I have not had that issue, but since I have an analog meter I use it instead of my DMM.... it is better for adjusting the efficiency coil for minimum current than most DMMs since it will show you minute changes that a digital display will hide in rounding to it's smallest digit.

One recommendation when you're done measuring the cathode current connect a new wire to the cathode pin, run it above chassis to a good spot to ad a fuse holder, ground the cathode thru a 1/4 amp fuse. Doing this will help protect the flyback from excessive current, and the fuse holder above chassis will also make a convenient current test point for future measurements... all you will have to do is remove the fuse and connect a meter across the holder terminals.

[ZenithNut]

Originally Posted by Electronic M

Line current and horizontal output cathode current have too loose of a correlation to be used interchangeably.

The cathode current can be measured by unsoldering the ground lead from the cathode pin of the h output tube socket then connecting the meter positive current terminal to that pin and the meter negative to ground (sometimes you should put a .47uF cap parallel to the meter ). The current will be in the neighborhood of 170mA to 230mA DC. make sure your meter has a 500Ma DC scale... I'm not familiar with your meter so check it's specs/manual. Also it is preferable to use an analog darsonval movement meter to a digital meter... it is a high frequency pulsed DC current on the cathode. An analog meter will average it well and be the same instrument that Sam's and the factory used to measure that. Some DMMs may get confused by non constant DC... I have not had that issue, but since I have an analog meter I use it instead of my DMM.... it is better for adjusting the efficiency coil for minimum current than most DMMs since it will show you minute changes that a digital display will hide in rounding to it's smallest digit.

One recommendation when you're done measuring the cathode current connect a new wire to the cathode pin, run it above chassis to a good spot to ad a fuse holder, ground the cathode thru a 1/4 amp fuse. Doing this will help protect the flyback from excessive current, and the fuse holder above chassis will also make a convenient current test point for future measurements... all you will have to do is remove the fuse and connect a meter across the holder terminals.

I will buy a 0-500 dc milliamp meter so that I may do that.

For the record though how can i set my meter up to look at the

[Electronic M]

Originally Posted by ZenithNut

I will buy a 0-500 dc milliamp meter so that I may do that.

For the record though how can i set my meter up to look at the

Look at the what?

[ZenithNut]

Originally Posted by Electronic M

Look at the what?

Do"h

I want to look at the overall ac current draw the set is using. I checked my fluke meter and it tops out at 320ma so an analog dc milliamp meter is on its way.

[Electronic M]

Originally Posted by ZenithNut

Do"h

I want to look at the overall ac current draw the set is using. I checked my fluke meter and it tops out at 320ma so an analog dc milliamp meter is on its way.

On tube sets that test is much less informational than solid state. A meter that can't measure 5-10A AC can't directly measure the line current the set draws. (also some DMMs that can do 10A only do DC and some only do AC so knowing which the meter can do is important)....

All that said there is a way to indirectly measure the AC that set uses with your present meter (assuming it has an AC volts range) get a 5W or higher, 1 OHM power resistor place that resistor in series with one leg of the cord (can hack up an extension cord to do this (and make a universal adapter) ) then with the meter in AC volts range measure the voltage across that resistor...You can then compute the approximate current using ohms law: I=E/R= measured voltage/resistance...Given resistance should be 1 OHM that means measured voltage should be approximately equal to the current flowing. The accuracy of the resistor, the accuracy of the meter, where you connect the meter along the wire will all introduce some error to the measurement, but it should give a decent approximation.