[Tomcomm]

Since my CTC2B FBX failure, I have attempted to replace it with a “modern” roundy FBX used in the CTC 10, 11, 12, 15, 16 and 20. The support circuitry for this FBX is totally different from the original CTC2 and CTC2B I’m familiar with. For starters, none of the CTC10 and later have width controls and must rely on component tolerance to assure proper overscan. They incorporate a balanced pair of windings with a 10ohm wirewound pot to center the raster +/- 2in. Even the crucial damper circuitry is totally different, using an ferrite-cored vari-inductor and capacitor values to accomplish horz linearity adjustment with an “efficiency control” that performs some sort of resonance?? All of this design rational is unfamiliar to me since my only TV reference ends with Fink, 1957.

In my present FBX test-bed module, the vari-inductor has no effect on anything over its full range, not good. I have the wrong RCA coil part number but have ordered the correct part, got to wait till it gets here. Horz linearity is very poor and the EHV Ultor will climb well past 40kv, resulting in severe arc-over of the little 3A2 EHV rectifier. With almost all post CTC10 roundys using this FBX with many circuit variations, surely some members have experience with these “modern” FBX configurations. All replies welcomed……Tom