5E3 hiss/buzz on max volume with no guitar?

[theundeadelvis]

When I built my 5E3 I had a very similar problem and it turned out to be the input jack wiring. It was the most awful hissing, buzzing, hard to describe noise. Like a donkey getting electrocuted.

[sliberty]

Keep in mind that the Express has no 68K resistor on the input. it is a part of the 5e3 circuit, but I bet it would work without it.

[muchxs]

Keep in mind that the Express has no 68K resistor on the input. it is a part of the 5e3 circuit, but I bet it would work without it.

The Express has no 68k but the late Mr. Fischer was brilliant when it came to layout. It's a minor miracle that it is what it is and it does what it does. Every other guitar amp I can think of uses gridblockers.

The way internet forum logic works is that if under ideal conditions something can be made to work it should work for anyone under any conditions. IF the exception is the rule then I should be able to defy the law of gravity, I'll fly just fine until the ground rises up to meet me!

[sliberty]

The way internet forum logic works is that if under ideal conditions something can be made to work it should work for anyone under any conditions.

My philosophy is the opposite - if one guy was able to make it work, "it can be made to work by others". But not all will be able to make it work.

Layout is king as you implied. Like I said before, the 5e3 circuit is not where the noise comes from. Its the 5e3 layout. Leo was no genious when it came to layout in the early days. But a nicely modded layout for a 5e3 circuit can be very quiet.

And a poorly laid out Express can make as much noise as a 747 despite KF's design.

[muchxs]

The way internet forum logic works is that if under ideal conditions something can be made to work it should work for anyone under any conditions.

My philosophy is the opposite - if one guy was able to make it work, "it can be made to work by others". But not all will be able to make it work.

Oh, no doubt. But for the most part it's like the old EVH quote where he said, "Screw the rules!" That's easy to say if you're Eddie Van but he left something out. The part he left out is "First learn the rules, don't ask why". Next, when you know the rules by heart figure out which ones you can break. You won't have to ask why at that point, you'll know.

I forgot to ask, Steve... did you leave the gridblockers in your 5E3?

[sliberty]

I forgot to ask, Steve... did you leave the gridblockers in your 5E3?

Of course I did
In my case, I quieted the amp down strictly with layout and the pretty standard approach to heater hum rejection (false center tap). The rest of the circuit remained untouched. I just didn't think that the gridblockers were the issue for nickt.

[muchxs]

I forgot to ask, Steve... did you leave the gridblockers in your 5E3?

Of course I did
In my case, I quieted the amp down strictly with layout and the pretty standard approach to heater hum rejection (false center tap). The rest of the circuit remained untouched. I just didn't think that the gridblockers were the issue for nickt.

Maybe they're not. That's just it, until that possibility is eliminated we don't know, do we?

I have a difficult enough time troubleshooting even with the amp right in front of me. I've "inherited" other people's problems, for instance they'll say, "It's not putting out full volume and it's very distorted. We've tried EVERYTHING!"

With the amp on my bench it becomes obvious that while they didn't try everything they tried a lot of things. If they tried everything it would work correctly. "Everything" usually involves fresh tubes and maybe fresh caps, then maybe they broke out the ol' soldering gun and disturbed some solder joints. Usually if I go through it with a tried and true troubleshooting template and if I'm having a good day it turns out to be something simple that another tech missed. If I'm having a bad day I have a restoration project on my hands.

My point is that if it isn't close to stock or it's a "replica" that deviates from stock... make it close to stock first so we're all on the same page.

[nickt]

Ok two steps forward and ten steps back!

Added snubber resistors and the oscillation disappeared Yay!! (I think).

After about 15 minutes of my brother in-law's playing the amp went dead (was it suicide? ).

Basically it now blows fuses with no tubes so there's either a short or a duff power trannie (which could explain why I thought it was a tad "quiet" initially).

More as it comes to hand.

[CaseyJones]

Ok two steps forward and ten steps back!

Added snubber resistors and the oscillation disappeared Yay!! (I think).

After about 15 minutes of my brother in-law's playing the amp went dead (was it suicide? ).

Basically it now blows fuses with no tubes so there's either a short or a duff power trannie (which could explain why I thought it was a tad "quiet" initially).

More as it comes to hand.

Oh, bummer. Did it smoke?

[nickt]

Oh, bummer. Did it smoke?

Not that either of us could smell so I'm keeping my fingers crossed.