Any ideas about how to solve this problem?

[Giulio Maiocco]

Hello everybody,

after the 27" TV restoration saga, I have a new toy I'm bringing back from death, this time it's an interesting and most unusual (at least in Italy) TV/radio combo from 1953.

A previous tech in a past "repair" session ripped apart and lost a ferrite cored transformer (I circled it on the circuit diagram attached) that supplies sync pulses coming from the horizontal output stage to the cathodes of a 6AL5 phase discriminator tube . Also, the power autotransformer was rewound not correctly, so some voltages were completely abnormal. I took this apart, calculated the turns needed (I didn't have the original specs and I hate when this happens, believe me!) re-rewound the correct way, this was the simple part of the many problems I found

Short of finding another of these transformers, that I think is like finding the proverbial hen's teeth, is there a possible way to modify the circuit to achieve the correct operation of the horizontal section? I have a positive going 220Vpp pulse shaped waveform source available from the horizontal output transformer if that helps, but I would prefer not to add another tube or, worse, solid state devices to accomplish this. Rewiring is fine with me.

I may also try to reconstruct from scratch the missing transformer, but honestly I don't have the faintest idea of the needed turns ratio and number of turns of each winding

Please, can also anyone guess at the phasing of the winding on the HOT's cathode? Would it be connected "aiding" the primary winding or is it connected 180 degrees out of phase? What would be the effect of this winding? It's only 16 turns with about 100Vpp.

Best regards

Giulio Maiocco

[Don Lindsly]

That TV sure uses a lot of parts. Take a look at some mid 50s US TV schematics. There are lots of models with much simpler circuits for horizontal control, particularly portables.

Rewinding the power transformer is a major accomplishment. Good work. Don

[cbenham]

Originally Posted by Giulio Maiocco

I may also try to reconstruct from scratch the missing transformer, but honestly I don't have the faintest idea of the needed turns ratio and number of turns of each winding

Please, can also anyone guess at the phasing of the winding on the HOT's cathode? Would it be connected "aiding" the primary winding or is it connected 180 degrees out of phase? What would be the effect of this winding? It's only 16 turns with about 100Vpp.

Some US sets used a transformer like the one you circled to feed push pull H pulses back to the 6AL5 AFC phase detector. Probably 50 to 100 volts peak to peak on the centertapped side. This is a guess.

I'll also GUESS the voltage going to the HOT cathode is + going. This is based on your drawing showing the winding feeding the EY51 Plate which is 'drawn' as being in the same phase, if the drawing is correct.

Best Luck,
Cliff