RCA CTC-5 Flyback Melting

[TVBeeGee]

Some have written here that it is normal to see some melted wax around 1950's RCA color flybacks. How much is normal?

When seeing a demo of this CTC-5AA (Deluxe) chassis prior to purchasing it, we heard a loud bang as the CRT came up and saw high voltage and horizontal sweep, but no vertical deflection, so we immediately shut it down.

When doing a physical inspection today (long before I will attempt to power it again), I noticed bright yellow wax that apparently has dripped from the flyback upper coil onto the lower. Bright yellow "stalagmites" can be seen in the first picture. The second picture shows the bottom of the flyback, where bright yellow wax can be seen oozing around the sides of the lower coil.

Wow. I'm pretty disappointed. How close to disaster is this flyback?

I've been unable to find any ruptured caps to account for the bang and missing vertical, the vertical pots seem OK and the ohm readings on the vertical output transformer look reasonable. Could a failing flyback have caused the vertical loss?

Other than horizontal efficiency tuning and minimizing the HOT current, can anything else be done to extend the life of a flyback with this much melted wax? Yikes!

[Electronic M]

I've seen worse flybacks work and live for years.

Most color sets use the B+ boost (which is made from energy recovered from the flyback) to power atleast part of the vertical so if the boost is dead or weak that can kill the vertical.

Make sure the H output cathode current is atleast 10mA lower than the Sam's maximum and of course set it to minimum.... adjusting drive and linearity is good but you may also want to grab a variac and vary line voltage up and down from a starting point 117V to see what line voltage gives Lowest H out cathode current while maintaining full horizontal deflection. Switching from tube to SS HV and focus rectifiers reduces load on the flyback and cathode current and heat since those tubes normally draw their heater voltage from flyback windings.
On my CTC5 special I have added a HV adjust potentiometer. The CTC-7* has a HV pot and is almost the same circuit as the CTC5 special...all I had to do is remove 1 resistor and replace it with another resistor in series with a pot (which I had to drill a hole to mount)...my set with the reg pulled and a medium brightness picture can produce 22KV (other sets that used the same CRT were designed to supply 25KV) and IIRC the CTC5 super schematic falls for 19-21KV before installing the pot it ran at 18KV and afterwards I set it to run at 21.5KV. The HV regulator works by sensing HV level (IIRC boost varies proportionally and is the control reference) and increasing the load on the flyback to reduce HV level....so the less the regulator lugs down the HV the less load there is on the flyback and the cooler it runs... just don't exceed the maximum schematic recommend HV level by more than 2KV as that could strain the HV insulation on the flyback and cause harm.

*Both the CTC-7 and CTC5 super schematics are posted on earlytelevision.org under color sets under technical documentation under RCA....I used those documents to figure out how to copy over the CTC-7 HV adjust pot circuit to the CTC5...It is easy.

[TVBeeGee]

Thanks for the tips! Got another question: What is the whitish stuff that's coating the leads of the flyback? Is that some sort of mold? Leftover residue from a cleaning agent? Degradation of the insulation?

[TVBeeGee]

Hey, if the 6BK4 HV regulator wasn't working, then when the TV was powered on for the demo there would be no regulator and no CRT HV current (CRT still warming up...it's weak) and so there would be no load at all on the HV. Could HV levels rise quite high under such conditions, high enough to cause a bang-type arc perhaps around the metal CRT, right before the CRT came up? If so, that might explain why I can find no component that appears to have ruptured or burned. Anybody know how much HV can be generated by a CTC-5 with no CRT load and no shunt regulator load? Maybe my 6BK4 is dead, or else coming up much slower than the H-OSC, HOT and HV regulator. Sound possible?

[old_coot88]

My first thought when you said there was a 'bang' (or very loud 'SNAP!') was a high voltage arc, like through a pin hole in the anode lead insulation, or a pin hole in the 3A3 filament winding insulation.

[Electronic M]

The white stuff is probably plasticizer leaking out of the plastic tubing on the wires that has gathered white dust or the same stuff 'knob fungus' is...or in short old plastic being normal old plastic.
A lot of sets the internal wiring and sometimes the cord will get sticky from plasticizer....my favorite pair of Sansui classique 1500 tower speakers have a wood grain vinyl covering that continuously releases plasticizer...I clean it and in a month or so it is back... leave it long enough and it gets hairy with dust bunnies and lint.

If only the HV reg circuit was malfunctioning then the CRT would still load the HV...If the CRT was cutoff or it's heater was dark you probably could not get over 25KV out of it...I don't think mine could do more than 23 with the CRT dark and the reg pulled. A brand new clean set should not make HV snap at 25KV, but an old set with conductive dirt arcing paths, degraded insulation etc that has never seen more than 19KV that is now suddenly getting say 23KV is a horse of a different color...

The snap may have been HV. If it only happened once there's no sense in worrying about it, just troubleshoot it as though you have no memory of the set before today and it magically appeared in your house (it's more fun that way too...look santa brought me a CTC5! ) . If the sound reoccurs regularly track it down with avengence.

[JohnCT]

Originally Posted by TVBeeGee

Some have written here that it is normal to see some melted wax around 1950's RCA color flybacks. How much is normal?

I don't think the wax drippings offer much in a way of determining how the flyback's condition is or how long it might last if good.

I've seen flybacks horribly cracked and split with a small mountain of wax underneath that were fine, and I've seen them look almost new and have a shorted turn inside.

John

[Eric H]

That's not much wax, but it does look fresh, it might bear investigation as to why it's getting hot. It appears to have been recapped already?

It also wouldn't hurt to clean all the black grunge off the tire before it becomes conductive and starts arcing.

[bgadow]

My CTC-5 has more drippings than that but I don't think its added anything to the pile in the time I've had it. I wonder if some sets didn't lose a lot right off the bat, and then settle down. But like Eric said, I'd sure investigate and make sure it isn't running hot. The good news is the 5 isn't known as a flyback killer.

[JohnCT]

Originally Posted by bgadow

My CTC-5 has more drippings than that but I don't think its added anything to the pile in the time I've had it. I wonder if some sets didn't lose a lot right off the bat, and then settle down.

Back when these were new, virtually no one had central air and very few people even had window or wall units. I have a feeling most of this is a combination of running in a hot room over many continuous hours that caused most of the wax expulsion.

I'm not sure if these flybacks can generate enough heat on their own in a couple of hours to melt wax.

John

[TVBeeGee]

Thanks everyone for the terrific observations and advice, so far. Please keep it coming. Nice to know that CTC-5 isn't so infamous for smoking flybacks. Sets my mind at ease a bit. I'll be sure to check current when powering up horizontal for the first time, but after a good overall cleanup.

Any advice on best way to go about cleaning the HV cage? It seems it would be a bad idea to use anything on the flyback that would soften its wax, be absorbed into the paper, or cause the dirt to be absorbed. Hmm. Maybe just brushing with a toothbrush while being very careful not to snag its leads???

[TVBeeGee]

Forgot to answer Eric H. Yes, the chassis was recapped two owners ago. Looks to be a pretty thorough and well done job, but I'm not sure how long ago it was done. The seller didn't have any of this info. I wish I knew more about the history of this Wingate, especially who owned it originally, how it got to Florida if purchased elsewhere, even when the recap was done and who did it. Was it an owner who did the recap? It looks as if some pride was taken in its execution. Strange feeling to be the new owner of something that has so much history, yet is mute. If these tubes could only talk, what stories would they tell?

[Electronic M]

I clean flybacks and everything else with isopropanol (rubbing alcohol)... It dissolves dirt and grease and evaporates fast.