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Originally Posted by StarquestMan
I went and checked the voltages coming off of the secondary, other than the heater, there are two sources. One is for the neck board and is listed as 195.5 volts. I read about 192-193 with a picture. The other was a 14 volt supply for the ICs on the main board, I read a fairly stable 14.1-14.3 volts.
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Those are certainly in the ballpark. I would double check the heater voltage though using a TRMS meter. It should read 6.3VAC (or whatever the CRT uses for heater) and not a tenth over. A tenth or so under is fine, but if you have to tweak things to get the heater on the dot, do so for tube longevity.
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I came across some interesting info here
https://www.repairfaq.org/REPAIR/F_m...tml#MONFAQ_018
It mentions that beam deflection in a CRT gets "stiffer" at higher voltages resulting in a smaller picture both horizontally and vertically. since the service manual states that the HV is non adjustable and is specified as 22.2 kv for the original flyback, I wonder if the output of my new flyback is ok for the secondaries but a little too high for the HV part?
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Possibly. In any case, a couple of KV high shouldn't make a dramatic difference in picture size, at least not enough that the circuit adjustments wouldn't compensate for.
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I had always assumed that the screen pot on a flyback fine tuned the high voltage output, but now I realize that this isn't the way it works, unless i'm mistaken.
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No, the G2 or screen adjusts the DC to the second grid of the gun, and the F adjusts the voltage to the focus element. There are no other adjustments on the fly.
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looking at the data for an HR7718 flyback shows an output of 24.5 kv. However I don't necessarily trust their specs because I do remember watching a video of someone repairing a 1990 Samsung TV with a failed flyback. He showed the Sams Photofact specs for the OE flyback output and the part number for the replacement. I went and crossed this number on HR Diemen's site and it listed a voltage that was about 7kv lower if I remember correctly. Im thinking that a high voltage probe would be a good tool for me to buy next.
Im not so sure how I would correct this if it does turn out to be the issue? turning down the B+ would lower HV but throw off all the other voltages.
I feel like I am learning quite a bit from all this though 
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The turns ratio of the secondaries set up the voltages. If your replacement fly has more turns on the HV winding, it will have more HV than the original, all other things being equal.
At this point, you can raise the value of the retrace cap across the horiz output transistor to drop the HV and this should also give you a bit more width. The vertical should be easily adjustable with no circuit changes. You will lose a bit on the other flyback secondaries, but those will have little to no effect generally unless the HV drop required is significant.
A HV probe in this case would be nice. Ordinarily, you can test HV by measuring the heater voltage. If the flyback is original and working properly, you can tell by an accurate reading of the heater what the rest of your voltages are. The CRT being very particular about heater voltage, the designers are very good about setting the heater to 6.3VAC. In this case of course, we have a different fly and can't trust the heater or other secondary readings to verify HV.
John