• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Engl Fireball E625 noisy


2009-11-13 1:32 pm
I have an Engl Fireball E625 that has just had the filter caps and tubes replaced, and following the schematic biasing technique I'm getting 2.3 and 2.5vDC on those testing points. Valves are all behaving themselves even though there seems to be more blue hue than usual. I have read in many forums that the problem I'm getting is quite common in these amps however no one has found a solution. When the ultra channel is used it is noisy hum and seems to be microphonic, I am using EH12ax7's and I have tried swapping them out with others but the problem is always the same.
I have taken some voltage readings as follows:
V1 pins 1 & 6 = 97vDC & 84vDC
V2 pins 1 & 6 = 217vDC & 162vDC
V3 pins 1 & 6 = 245vDC & 223vDC
V4 pins 1 & 6 = 252vDC & 261vDC

and for the power tubes I'm getting -41vDC for 415 and 422vDC on each tube.
readings were taken with volumes all turned down. Readings do not change after switching channels.

thanks for any help at all

Is the input on the E625 switched so that it's shorted when nothing is plugged in? If so, is the amp quiet with nothing plugged in?

If not, carefully try shorting the input with the amp opened up to see if that changes the noise that you're hearing.

What does the noise sound like that you're hearing? Is it 60Hz hum or 120Hz buzz (download some tones so you know for sure)? Are you located in an area where there are some competent techs who can look at it?

Has the amp always been like this?


2009-11-13 1:32 pm
yes when I switch to ultra even with nothing plugged in it still is noisier than the other channel but obviously much more evident when I plug the guitar in. It seems that there is too much gain and it whistles high pitch feedback even at low volumes. this with all the background hum that is absent on the other channel.