Hi folks - I've done this mod successfully on a number of JVC's - av and D series. The results are quite obvious and i love it. I am doing this on my KV-35s45 currently and running into a challenge. I am using a pre-built g1 mod board - I've got it set up like this:
- On the flyback
Im tapping the flyback on the -15v pin on the flyback - i measure up to -135v on the neck side of the mod board with the pot maxed out. I've also used the 200v pin and i get about -235v on the neck side of the mod board with the pot maxed.
- On the neck board
i am tied into all 3 of the g1 pins from the neck side of the mod board
I have lifted the 2 resistors and 1 diode that are connected to pins so they are isolated
Adjusting G2 and G1 doing really do much of anything
- G2 doesnt really give more or less brightness like i usually see - adjusting has a very very minor impact on brighness where the colors get a tiny bit more or less rich, but its like a threshold, really can other be on one side or the other of the trheshhold - and even so the adustment is extremely minor. Too low G2 and the screen shuts off, too much and i get retrace lines (as expected) and the screen shuts off
- G1 mod pot does pretty much nothing on this TV- other than when i hit about -75v or lower it just shuts the screen off
** worth noting i have done a rgb mux mod - thats been running and fine for months.
Any thoughts or suggestions one whats going on or what i could do here?
Flyback and neckboard on pages 25 and 31 of this schematic
https://dn721906.ca.archive.org/0/items ... 105345.pdf
im using this mod board - https://www.rgbmods.com/products/g1-mod-kit
thanks!
CRT G1 Mod Problem/Help Requested
-
MercilessDeth
- Posts: 1
- Joined: Sun Nov 23, 2025 5:56 am
Re: CRT G1 Mod Problem/Help Requested
I don't have much actionable advice but I'm interested in this as well. This week, I RGB and YPbPr modded a KV-32V25 and in addition I installed the same G1 mod board you linked. My TV is an AA-2 chassis, so I think it's a pretty similar unit.
I'm tapped into the pin marked 10 on my flyback. It says "28V" next to it, but I looked at each pin with an oscilloscope and it was closest to the description of what I was supposed to be looking for. I measured just now, the pot isn't all the way to the right (maybe 80 - 85%), but it's at -165 V on the neckboard side so I think that part is alright. On the neckboard, I desoldered the white connector and lifted all 3 G1 pins and tied them together and connected to the mod board.
- With G1 turned as far as I have it, I'm a bit concerned (though maybe I shouldn't be) that I have to turn G2 on the flyback almost all the way up or the screen shuts off
- I also don't really notice a big difference. However, this is the first CRT that I've performed the G1 mod on, so I'm not sure where I should aim my expectations. That said, it does look "better" but I'm wondering if that's just a placebo.
- Due to the size of my set, and because I don't have a mirror, I have to perform any adjustments and then walk around to observe the effects. I can reach the back of a 27" and still see the front a bit but this one is too large. So it makes it tougher to A/B compare
One thing I just thought of, I have a colorimeter that I use for color calibration, I could set a 100 IRE white patch and try to take some brightness measurements while adjusting the G1 pot. I'm not exactly sure the expected results in this regard. Since G2 adjustment is required when making larger adjustments with G1, this might not be apples to apples though.
I'm tapped into the pin marked 10 on my flyback. It says "28V" next to it, but I looked at each pin with an oscilloscope and it was closest to the description of what I was supposed to be looking for. I measured just now, the pot isn't all the way to the right (maybe 80 - 85%), but it's at -165 V on the neckboard side so I think that part is alright. On the neckboard, I desoldered the white connector and lifted all 3 G1 pins and tied them together and connected to the mod board.
- With G1 turned as far as I have it, I'm a bit concerned (though maybe I shouldn't be) that I have to turn G2 on the flyback almost all the way up or the screen shuts off
- I also don't really notice a big difference. However, this is the first CRT that I've performed the G1 mod on, so I'm not sure where I should aim my expectations. That said, it does look "better" but I'm wondering if that's just a placebo.
- Due to the size of my set, and because I don't have a mirror, I have to perform any adjustments and then walk around to observe the effects. I can reach the back of a 27" and still see the front a bit but this one is too large. So it makes it tougher to A/B compare
One thing I just thought of, I have a colorimeter that I use for color calibration, I could set a 100 IRE white patch and try to take some brightness measurements while adjusting the G1 pot. I'm not exactly sure the expected results in this regard. Since G2 adjustment is required when making larger adjustments with G1, this might not be apples to apples though.