Something wrong with Express?

[Ukko75]

Hi!
I got this kind of problem. Playing with my strat it sounds pretty good vith guitar volume under 8, but when volume is on 10 sound gets thin and harsh like some of the mids diseappear. Same things happends all single coil pickups. I have SM 59 humbucker on bridge and it sounds much better.

With my LP it sounds way better, but it still does act like this: volume under 2 sound is clear and balanced 2-4 sound gets darker and it starts to break and there comes way moor bass 4-8 sound get almoust muddy on bass strings 8-9 it is guite good but on 10 it gets thinner and harsh top end comes present and muddines diseappears. I dont know is this normal acting?

Amp settins all pots at 12 o´clock

I am wondering could lead dress cause thing like this? It should be pretty accurate to compare the pictures on Francesca. I tryed lot of things to get this solved but now i dont know what to do next?

Please let me know if anyone have suggestins or having same experiments.

[sliberty]

Sounds like there could be an oscillation, which COULD be caused by lead dress. Time to get out the chop sticks.

[Ukko75]

I tried move wires around, but no help.

Is this normal, that power tubes have a blue glov when amp is on. Then when the guitar signal comes thru other tube gloves less blue and the other tube gloves moore blue?

Might this be a sign of oscillation?

[geetarpicker]

The blue glow is normal. How about an audio clip of the issue? Typically if you have an oscillation problem IF it's at a very high frequency, like almost above the range of hearing you will however face a clean tone that is never very clean with almost a lofi nature to it. Basically the oscillation clips the amp and modulates the clean signal into a mess. Still it's hard to descibe so an audio clip might help us. If the amp has a more low frequency oscillation issue you would hear an obvious squeal.

[Reeltarded]

Or input ground reference?

Snap a couple pics from the rear edge of the chassis towards the front at an angle where all the controls are visible when you have it apart again.

[Ukko75]

The audio clip could be best way to show how does it sound. But i only got my telephone to record at, but i will try when i got the time. Here is couple of pictures. Hope i understood right what part you ment.

[Reeltarded]

Exactly what I meant about the angles. Let me go get a food to eat and come back to stare for a minute. My head is pounding! I hate migraine days.

[Reeltarded]

I don't see anything that would tell me I was right.

What I do see is a lot of joints I would reflow with a VERY fresh tip and a VERY hot iron. 20 minutes worth of work would clear up many little frittering noises that might add up to most pf your teouble.

Instead of chopsticking wires, have someone else play the guitar while you chopstick joints, and even whole areas of the board. You will find some obvious points of intrest. The solder joints look almost dry in some areas. Whet the tip of your iron with a little touch of solder before reflowing each joint..

Hmm.. I know TWs have flying wires, but I like to dive them onto the chassis deck if they are longer than a couple inches. The routes are rightish in one plane, but some of those need to follow the path on a different plane.

[Ukko75]

Thank you for the tips!

Do you mean that i take solder iron whit a clean tip, put some solder it and heat again solderjoints whitout adding more solder?

Or should i remove old solder an resolder it?

I have very little experience with these things, and my english is not so good.

That was great idea to put someone else play guitar while chopsticking!

Do you mean the ground wire from volumepot to board that shoud run near the chassis and wich other wires do you ment?

[Reeltarded]

Look at other pictures of lots of finished amps. You will see how an average routing job looks and it will give you good ideas there. Not so many problems to work out there.

Leave the old solder. Clean your tip really well and then apply a little solder to it for every joint you reflow/touch up. Many of them look like they need a little more, and I swear I see flux or discoloration from heat on them. These things need a positive contact. Some of the trouble is probably there.

Make sure your iron is very hot so contact time is short to reflow. No need to burn the posts or the wire.

I am Amercian and I speak terrible English.

I think you can find problems if you can get someone else to just plunk on the guitar while you push around with a wooden stick. MUCH more safe as well. Easier to concentrate and be careful.

[M Fowler]

You didn't use heat shrink tubing on your coaxial cable from input to V1 so make sure that braiding isn't touching. Also add a 33ohm grid resistor on that input coax right on the V1 tube pin 7.

Add an 820 ohm resistor right on V1 tube pin 2, the wire from the wiper of the volume pot.

See if that helps.

Mark

[Ukko75]

I will resolder connections and chek that coaxial cable. Those grid stoppers i have tryed, and they did not help this problem.

[M Fowler]

I've always found that the presence circuit has been my main problem in the Express, it's very unstable. I wonder if decreasing the NFB resistor would make a difference for less NFB?

Mark

[geetarpicker]

You are running a bottom plate to shield the circuit?

[Ukko75]

Now i have done resoldering and it helped. Coax cable was ok. But the sound is not good yet, now i try to get somebody to play the guitar so i can try chopsticking.

Yes i have bottom plate.

I got this feeling that when guitar volume is 10 signal hits some part of the amp so hard that it smashes it to harsh distorted kinda sound. This is only feeling of it.