5E3 build-Very low output and no clean tone

[theundeadelvis]

Hello! I just finished up a 5E3 build using Loy Dockery's layout (attached, third amp on the list). I fired it up and there is sound. The problem is the the output is very low, and it is very distorted. There are no clean tones, and the distortion is very buzzy, farty. Any ideas where I should begin to look? I'm wondering if the shielded cable for the inputs I used could be the problem? I wanted something small in diameter, but the gauge of the inner wire is tiny (maybe 28 or smaller). Any suggestions are very appreciated. Thanks in advance!

[John_P_WI]

Hi, it is unlikely to be the input shielded cable.

What is the plate voltage on the output tubes? What is the voltage across the cathode resistor? What is the bias current through the resistor. Is the cathode cap polarity correct or blown?

What are the other voltages? With the amp turned on and starting at the output tube touch each grid with a DVM probe and move towards the input touching each grid. The disturbance noise should become louder with the volume is turned up as you head towards the input.

This should get you started.

John

[theundeadelvis]

Oops didn't have the power tube grids hooked up. Sometimes you gotta walk away for a bit and come back with a fresh mind.

Now the problem is when even plugged into just one channel both volumes affect the sound. When the plugged into the normal if you dime the bright volume you get horrible squeal and a pulsing thump?

[Allynmey]

Elvis, you need to post a voltage chart. This will almost always tell the tale.

[brownnote]

OK, you have oscillations.
The control interaction is typical of the 5E3 circuit, so when you get your other stuff sorted out, that will still be the case, unless you re-wire the controls to a different spec.

[CaseyJones]

Now the problem is when even plugged into just one channel both volumes affect the sound. When the plugged into the normal if you dime the bright volume you get horrible squeal and a pulsing thump?

The volume controls are interactive on a tweed Deluxe. Usually it's not noticable until 9 or 10 (out of 12, it's a tweed remember).

Still, it sounds like you've got an oscillation problem. Check and re-check your layout. The last one I built was dead quiet which is actually a big joke... I had a faulty pilot light so the pilot didn't light on initial power-up. The amp was so quiet I didn't notice it was even working until I saw that the filaments were lit. Everything else worked like a charm on the first try.

[El_Martin]

Hello Elvis!

Recently I watched a thread in a German forum. Similar problem.
Checking the voltages lead to a wrong part in the PI. Extremely asymmetrical signal clipping.

For 5E3 there are a couple of voltage readings floating 'round the 'net.

Ciao
Martin

[benoit]

The volume controls are interactive on a tweed Deluxe. Usually it's not noticable until 9 or 10 (out of 12, it's a tweed remember).

What do you mean by saying the volume controls are interactive? I'm looking at the 5e3 schematic and don't see how the one volume could affect the other. I'm not disputing your claim at all, but could you explain it please?

Ben

[theundeadelvis]

Cool, I will check the voltages. I may also try the mix mod to the volume controls, but as it sits now it is unmodified. Thanks for the tips!

[pila]

The inter-action between the controls is part of the 5E3. Some different tonal effects are possible with that. Looking at the schematic, it's hard to figure why it works that way, but it does.
Regarding your squeel/oscillation, try reversing the plate leads from the primaryof the output transformer, the red and blue wires. Things don't always work according to the color on the schematic.

Regards PILA

[skeezbo]

Benoit,
On the Tweed Deluxe that I had, the volume control on the channel not being used seemed to effect the overall tone more than the volume as you swept it. I think the channels interact because there are no 270k resistors mixing the two channels like there are on the tweed Bassman.

Skeezbo

[theundeadelvis]

OK, here are some voltages. Mine vs. the measurements I found on a schematic at homebrew tweaks.

V1 (just noticed I have an AX7 he has an AY7 if that makes a difference)
pin 1 172.4 vs 120.4
pin 6 172.6 vs 122.8
pin 8 1.45 vs 2.0

V2
pin 1 166 vs 167.4
pin 6 211 vs 175
pin 8 49 vs 70.5

6v6
pin 3 362 vs 380
pin 4 339 vs 338
pin 8 22.47 vs 21.7
6v6
pin 3 362 vs 392
pin 4 339 vs 339
pin 8 22.47 vs 21.7

Filter caps are
mine 378v, 339v, 260,
his 391v, 339v, 242v

Let me know if I should take any other readings.

I also noticed I get really bad hum when the guitar is not plugged in.

[rfgordon]

A bad hum with no cable plugged in means the input jack is not wired correctly--it should short to ground with no cable plugged in.

[theundeadelvis]

Rich you made a light bulb go off. I used mono switchcraft jacks and didn't even think twice about it. Duh! That'll make some noise.

Here's a couple pics. If anyone sees any major lead dress issues please let me know. Thanks again!

[theundeadelvis]

Using the correct input jacks pretty much took care of everything! Sounds pretty sweet! I've got some hiss, but it's not terrible. It's only noticeable with the volume pretty high. Thanks for all the help!!