Hi John Folsom,
That makes two of us looking for a 20BP4! I have a dud 20BP4, but can't quite bring myself to spend $1000+ to send it to RACS for a rebuild, and I suspect that possibility won't be there much longer. On the other hand, I suspect eventually a set with a 20BP4 will turn up, and for not that much money. Too bad this one turned out not to have a 20BP4.
I subbed a 19DP4 (purchased from John Marinello 5 years ago or so, if I remember correctly) into my Westminster, which is a reasonable sub. It doesn't really fill the corners of the 20BP4 mask, however, so I've often thought that a rectangular tube sub might in fact be a better match. A 21 inch rectangular tube might just fill the mask nicely.
Next problem is that the original deflection yoke won't produce a big enough raster to fill the screen of the 66 degree 19DP4. I'm going to return to that problem again one of these days to see if lowering the high voltage may do the trick. May need to sub the yoke as well, so that will be a bit of a project in itself. In the mean time I'm OK with a slightly too small raster.
Good luck with your search for a 20BP4. Hope you find two of them!
