How the Vox night train NHT15 fizz issue was beaten.....revisit?

[vinyl ritchie]

I've read the 17 page discussion on how the Vox Night Train fizz was beaten using 3 grid stoppers (33k on V3B, 33k on V4B and 1.5 meg on V4A ). I thank and admire the skill of the people involved. I've also looked at the photos posted. I have pretty basic skills, but I think I can do it observing the relevant safety aspects. I don't know where to cut the third trace, the one for the 1.5 meg on V4a. I believe it's c10/r19 node. I also wouldn't mind checking that my other connections will be correct. Any discussion and/or help would be appreciated. I pushed the old thread to page 18 but to no avail.

[Chuck H]

Please link any referenced threads so that responders can brush up on the information therein. It may matter.

[vinyl ritchie]

Thanks Chuck H for the guidance. Link supplied.

On page 16 of the link, the member 'Kleuck' summarizes the addition of the 3 grid stoppers and track cuts as:

"No, you don't have any resistor to replace : you must add them. Between the junction of c27/r36 you have the connection to the grid of a triode : so between this node and the grid (pin2) you must cut the path and add a 33K resistor. Same with c22/r27, this node to be connected through a resistor to the grid (pin7) Same with the c10/r19 node to the grid of V4B : 1,5 M here."

I have then been studying the photos provided by member 'Ross Grey' on page 17 of the link provided, trying to check the above statement with the photos. My skills are basic. I can see the 2 track cuts in the photos, which I think are for the 33k's, but can't see the one which I believe is needed for the 1.5Meg. The 1.5Meg, I think is out of focus on the left of the photo that has the grid stoppers. I can only see 2 track cuts on the other photo. I can repost those photos with arrows if need be. I have no idea if that's allowed as they are Ross Grey's photos. This is the first online forum for anything I've ever joined!

[vinyl ritchie]

A 12AT valve in V3 and one in V4 is the best combination I can do to eliminate the fizz, but it's still there. Perhaps just makes a better range for edge of break up. The amp would sound great like this but for the fizz.

[g1]

Does your board exactly match the one in the photos? There is also the question of the other track mentioned by Carlossdrri in post #259 of the other thread (pg.18)
I think you may have to lift one end of R25 because of the trace under the V3 socket.

[vinyl ritchie]

Thanks g1, appreciate the input. I will check all of that. Yes, I saw the post by Carlossdrii on page 18. I will try and get some photos of my own board up soon.

[vinyl ritchie]

I will keep adding info in case it helps anyone else. I've taken some photos of the night train board, but can't seem to add them using the 'media' section. I've contacted admin. It's the same board as the one posted by others(without mods, original factory as far as I can tell). Meanwhile I've gone back to changing tubes etc. I now have a 5751 in V3 and a 12AY in V4. I have also changed the speaker to a V30(orange 1x12). The speaker change has seemingly reduced the fizz. Significantly. Even at tricky settings. Gain on 3 o'clock, master on 12, triode mode. The greenback I have been using(tried closed and open cab) was from an AC15c1. Maybe that has not been played in as much. It's in great condition. I've played it quite a bit, but was from a mates amp. I've had the V30 for a long time though. Surely the night train was developed with the Greenback in mind? That may not even be in the thinking of development or marketing I guess.

[g1]

Right below the text box there should be an 'upload attachments' button. You should be able to add your photos that way.

[vinyl ritchie]

I tried that but the allowance in data is too small. I tried converting the images to a smaller size, but clarity is lost. It seems a small amount(976kb) for an image. I don't know my file types well enough.