RCA 21CT55 #8802897 is Dead

[yagosaga]

Originally Posted by ctc17

I know this is a long shot, but, how about rewinding? Has anyone ever successfully rewound a fly or had it done by a transformer company?

Hi,

some years ago, I visited Marcel van Grinsven in s'Hertogenbosch. He had manually rewound the primary coil of a burned flyback for a 90° Delta shadowmask color tv set. The rewound flyback looks lousy, but it worked! I saw the set working with this flyback.

Meanwhile, he could replace the rewound flyback with a spare one.

I learned that rewinding a primary coil seems not as difficult as it looks like. The reclacing of the EHT coil with a coil from an other flyback model is much easier since the technical values are more similar. I have even replaced a Sojvet EHT coil for a coplor flyback with a ten-years older German EHT coil of a quite different color tv set.

Kind regards,
Eckhard

[old_tv_nut]

Originally Posted by yagosaga

Hi,

some years ago, I visited Marcel van Grinsven in s'Hertogenbosch. He had manually rewound the primary coil of a burned flyback for a 90° Delta shadowmask color tv set. The rewound flyback looks lousy, but it worked! I saw the set working with this flyback.

Meanwhile, he could replace the rewound flyback with a spare one.

I learned that rewinding a primary coil seems not as difficult as it looks like. The reclacing of the EHT coil with a coil from an other flyback model is much easier since the technical values are more similar. I have even replaced a Sojvet EHT coil for a coplor flyback with a ten-years older German EHT coil of a quite different color tv set.

Kind regards,
Eckhard

I would like to second this idea - if the primary winding is separable from the secondary. The primary winding depends mainly on its inductance for proper operation, since the distributed capacitance is not that large, plus, it is essentially in parallel with the yoke inductance. The secondary (HV) winding is tuned by its distributed capacitance, which means you need the same materials as well as the same winding configuration to get the original result in rewinding the secondary. Using an existing good secondary coil in case that has failed also makes sense, since you will get both the designed inductance and distributed capacitance.

I wish the OP good luck, but also want to say that I personally never would raise the B+ , HO current or HV to improve the picture. HO and HV stages are just designed too close to nominal to do that IMO.

[Zenith26kc20]

This may be a dumb question but I'm curious.
Have you tried removing the high voltage winding (physically) and running the set without the winding to see if the current rises after a few minutes? On most failed flybacks I have encountered, the secondary breaks down and burns up. This could leave the primary and the pulse windings intact (could I say).
If this is the case, trying just the high voltage winding from another flyback may be the cure.
I "hot rodded" a Magnavox solid state years ago with great results. It died from a shorted (AC hot to chassis) FM tuner which I temporarily connected into the system (stereo and TV all together) and fried the TV and preamplifier.
My two cents.....
I am sorry to hear of the flybacks demise.