Quote:
Originally Posted by John Folsom
John, if reversing the yoke leads does not work, I wonder if you could try rearranging the yoke to operate in parallel, without the balancing cap? How does the inductance of the replacement yoke compare with the original? What Sams Photofact is your set in?
These RF HV supply sets for the 10" and 12" CRTs were oddball sets even in their day, and I suspect the Thordarson/Merits/Stancors of the day did not consider it worthwhile to make these low volume parts.
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The folder is number 11, set 96. I find the SAMS more difficult to read than the Sylvania or Wallace schematics.
The inductance of the RAM yoke is the same as the Sylvania. If I were to rewire the coils in parallel the resulting inductance would be somewhere between 1/4 to 1/2 the original inductance, depending on how much mutual inductance there is between the two.
I'm doing laundry tonight and when I do laundry I don't have access to the trap door to my basement so I won't get to try it tonight.
Roger Dreyfoos sent me some info from a RAM guide to yokes that is pretty interesting. It talks about residuals fields in some that need to be eliminated. I thought that was my problem, but now I think it's just a bad yoke to begin with, but no shorts.
It has an iron wire winding to form the core, that likely accounts for the low ring test. I don't think there's a short because both half coils test the same for inductance and number of rings. It probably doesn't shield well against the focus magnet which causes a rotation in the raster.
The yoke also appears to be deformed, I'm not sure why that is, but it is also off axis from the housing. The off axis problem is just the way it was assembled.
It also appears that it is not cosine wound, which doesn't help the focus either.
I'm still going to check it out with a hall probe, but using the digital compass on my watch suggests that the residual field is less than the earth's field. I don't think a residual field is the problem. If it turns out to be stronger than that, I might try degaussing it.
John