Building a new Express check the pix !

[Curranproducer]

here is the "I am so excited to play it I cannot wait" video clip !!!!!!!!


http://youtu.be/7jLUSuiPKrs

[Curranproducer]

so I found that it only squeals when I have nothing plugged into it, AND I get radio stations when the guitar volume knob is turned down. Hints or ideas? other than that this thing is killer!!!

[martin manning]

Do you have a grid stopper on the input?
See also https://tubeamparchive.com/viewtopic.ph ... ht=ferrite

[Curranproducer]

well I got the 1M on the input jack but nothing going to the grid of V1. I will have to look into the ferrite bead out of curiosity.

[vibratoking]

The 1Meg isn't the stopper. You could try ferrite or you could put something like 33k or 22k in there to see if it solves your problem. Put it right at the tube pin for best results.

[Curranproducer]

OK I got no problem dropping a grid stopper in there, BUT the schematic does not call for one(which I did think was odd) SO if it doesn't ruin the tones I got going on right now I will do so immediately !!!!!
!!!

[martin manning]

Try a little one around 1k ohm and see if that doesn't do it. I believe KF was known to do that occasionally.

[Curranproducer]

I dropped a 33k on the grid(right on th pin as a matter of fact, BUT to no avail. with nothing plugged in and the volume and treble dimed it squeals. when I drop the treble and volume back to the 3 O'clock position the pitch changes and then goes away. so this must be an oscillation of some sort correct? how do I hunt this down and clean it out?

[martin manning]

Did the radio reception go away with the input grid stopper? The squeal is oscillation by definition. A small grid stopper on the second triode is another thing to try. Mine has 22k on the input and 820R on the second stage (I had that backwards above). If that doesn't work, it's likely some kind of lead dress issue, do some chopsticking and see if you can find the sensitive area.

[Curranproducer]

the radio is gone! I did for get to mention that as I am more worked up aboot the osculation. I will grid stop the V2 pin 2 and see what happens there! cool!!!

[Curranproducer]

I would drop thet 820R on the Pin coming off of the volume control before the VA1 stage of the 1st 12ax7. so pin 2 of the 1st 12ax7?

[martin manning]

Yes. You could use coax for that lead too.

[M Fowler]

I also use shielded wire for both my 33k V1 grid stopper and my 820R to volume pot.

[Curranproducer]

OK Chopstick testing!!!! with the presence,volume, and treble controls on 10 I stab around the heaters and can make the osculation go away when I touch the heaters on valve 1 with the chop stick. I feel like this is telling me to redress the heaters away from the tubes instead of between them like what my pix show.

[Curranproducer]

I can do the shielded wire for the as well. no worries