So I have a 3fp7 and I tried it in my pilot and it looks pretty good however how would I get the tube to fill the whole 3 inches. Some mods of some kind ? It is a lot clearer but my IPad cannot handle light, it don't take good pics.

Comparing the datasheets for the 2 tubes shows serious differences in deflection factors between the 2. The 3FP- is a less sensitive tube than the 3KP-, so you would need to increase deflection voltages applied to the plates to get the same size raster.

The horizontal sensitivity of the FP is 221 Volts per inch, compared to around 115 Volts per inch for the KP. Vertical sensitivity is 163 Volts per inch for the FP, and around 85 Volts per inch for the KP.

Timmy,
I'm suprised that the your 3fp7 image quality is that good. I would have thought you would have more smearing due to the yellow phosphors' long persistence.
ED

Timmy,
I'm suprised that the your 3fp7 image quality is that good. I would have thought you would have more smearing due to the yellow phosphors' long persistence.
ED
Maybe the video was paused?

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Maybe the video was paused?

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Good point, with all the new modern video sources, its nothing to freeze the frame.

The image was not moving much at all but with movement it was still not bad and if I can get the image to fill the whole tube I think I would prefer this tube over the green. If its voltage that has to be increased to fill it I'm not sure if it can be done.

You can INCREASE the deflection voltages applied to the vertical and horizontal plates, or DECREASE the total accelerating voltage to get increased deflection (at the expense of brightness and possibly focus).

You can INCREASE the deflection voltages applied to the vertical and horizontal plates, or DECREASE the total accelerating voltage to get increased deflection (at the expense of brightness and possibly focus).

How exactly would I increase voltage from hv ?

How exactly would I increase voltage from hv ?

You do not raise the HV. You raise the deflection output amplitude. Or you REDUCE the HV. Either or a bit of each would work.

Unfortunately, the voltage that drives one of the deflection amplifiers is derived from the high voltage supply, so reducing the hv to increase the deflection sensitivity will also adversely affect the deflection in the vertical axis.
A real catch 22 situation.

jr

Well I can raise the feed back ring on the 1b3 to lower hv a bit and see if it fills in more , just to see really what I'm left with who knows it may be watchable and somewhat better then the green tube but it needs to fill in to find out.

You do not raise the HV. You raise the deflection output amplitude. Or you REDUCE the HV. Either or a bit of each would work.
Ok I lowered the hv and it did expand but not enough so how would I raise the verticle and horizontal deflection output. The simple way if possible I would not want to do a major mod.

Ok guys there has to be someone that can help me in trying to raise this deflection voltage to possibly use this 3fp7 crt if it sucks after doing this well I guess it's back to the green tube but I would like to try but have no idea how to get the voltage required to fill this crt face. The image in the other post shows how it looks while others say it was a still but I did watch the movement and there was very little yellow trails not enough to not be able to watch it. Where's the knowledge, compared to me you guys are the experts. :D

In short, you would need to increase the plate supply voltage to the vertical and horizontal deflection amplifiers, and probably adjust the drive signals/bias levels to those tubes to get more output. You want to end up with more voltage swing across the CRT deflection plates, without exceeding plate dissipation or voltage ratings of anything in the circuit. You will also need to keep the tubes within their linear operating region, to avoid distortion of the image.

This is the kind of work that doesn't have a cut and dried "answer" to spoonfeed to you. You are literally talking about re-engineering a portion of the circuit, and unless you have a good practical understanding of vacuum tube electronics, you aren't likely to succeed. Given some of the other questions you have asked about this set, it doesn't seem like you are quite there.

Spoon feed , really... :thumbsdn: that's ok I'll figure it out , to many people here claim to know so much And probably can't do half of what advice they are giving to another person. Because if so many knew of a way to do this I would have had a dozen replies. So I guess you would know exactly what to do............ If the last post was read I was not looking for a major mod..............

Sorry Timmy you took that answer the way you did but what N2IXK tells you is the truth. I doubt there is a person alive today that could answer your question off the top off his head without doing a bunch of research first, if there is someone I apologize! You want to re-engineer a proven circuit to do something it was never intended to do. There is NO easy answer to what you are asking and will involve a whole bunch of time looking at specs and lots of experimentation to come up with a circuit that might do what you want. I wish you luck and hope you get a positive result.

Gregb

I was only asking for a simple mod not a full blown one so I got my answer as I didn't know in the beginning. I was not overly serious I just wanted to know if it could be done simple, that was it. This pilot works great now I would be nuts to modify this set at this point with a huge engineering project and risk the whole set.