Curtis Mathes C20 Ctc 15/16 clone woes
 

Hello all,

I recently got a CM C20 ctc15/16 clone (it looks to have characteristics of both sets). So far I have a baseline of a good testing 21fbp22 Hi lite picture tube, an open circuit breaker, an open on/off switch, and a flyback with a shorted primary. Both leads of the primary are lifted out of circuit. It should measure 1 ohm where it measures .1 ohm as if you just short the meter leads together so unless im doing it wrong I say its shorted.

The flyback circuit is most similar to a ctc 15.

Can I rewind the primary? The secondary ohms out fine and is not burnt up or anything.

That circuit breaker is usually in the cathode circuit of the horizontal output tube. It will trip when it draws to much current to protect the tube and flyback. A loss of drive to the output tube, and a bad output tube can cause it to trip. A shorted primary is also possible. The 1 ohm sounds like winding on the bottom going to the HV rectifier tube. It is just 1 turn of wire and could easily be .1 ohm like shorting the leads. I would have to look at the schematic.

Best is to ring out the flyback with a tester. Here is another sneaky trick.
unhook the Hoz out primary & put the hoz section of another yoke in its
place. If the hoz out draws apx 200 ma ( see manual ) everything is good up to
there. Works great on SS sets too !
If it uses a double breaker it will have 3 terminals & a 4th to
the metal case so it needs to be soldered in. 2 terminals are the break point for
the AC or B+. The 3rd goes to the cathode of the hoz out. There is a resistor
inside that goes to GND. If the hoz stage draws too much the resistor gets hot
& pops the breaker.

73 Zeno:smoke:
LFOD !

Bill, the circuit breaker is physically broken, and doesnt pop in or out. Reads open on my meter.

Heres a screenshot of the dly in the schematic for my C20

I dont have a ringer BUT i have a o scope.

That ain't your primary! The primary is the 580 ohm between the H out tube top and the HV rect top, or the 5.5, .8 and or 6 ohm windings depending on who you ask.

That 1 ohm (might be .1 since there is a faint dot out front) winding is just a trigger pulse output winding that sends a signal to the color burst gate and possible H osc feedback...You could unhook that 1 ohm winding in any working set and the set would still work (albeit the color would probably be screwy).

Make sure the other windings are within 30% tolerance of the sam's and if they are the fly is probably fine (and you should proceed with the resto work). If that 1 ohm signal winding is not providing a pulse with everything else working you can probably wrap a few turns of magnet wire around the core to get that trigger pulse.

Most RCAs of the roundy era I've seen don't really protect the fly with a fuse or breaker...Usually, the breaker is on the B+ winding of the power transformer....A major cause of breaker failure is shorted filter caps just off the rectifier, shorted rectifiers, or once in a blue moon a horizontal issue. Most sets I see that have a bad breaker are on their 2nd or 3rd filter can.

Thank you again tom! Ill fire her up shortly. Did you ever find a blue lateral?

Alright guys I'm going to come back at.

So basically I was wrong saying the fly back is shorted. Its totally fine.

The set has audio. There's static and changing the channel knob makes noise. Currently there's NO raster.

The most obvious first reason is a positive g1 voltage on the HO bulb. I went back towards the horz osc and the voltages were off. I'm going to fire it up and check B+ Rails, and re check osc voltages. I'm pretty sure the vertical is running because you can audibly hear it. Woot!

The CM clone fires up and produces Hv and a raster. It's kind of odd but the ho cathode current is only like 100ma and adjusting the efficiency coil wasn't changing it. Its producing like 20kv. Raster is pretty bright.

I will have to so some serious cleaning. You can draw a little arc off the hv cage. Most likely the hv is tracing through dust/carbon. The hv is pretty noisy but it's all working.