Tube Amp Archive

The reading at pin 5 is -60V on all four EL34's

These readings were taken between pins 1/8 and chassis ground on the mV section of my Fluke meter. If i turn the pot the other way it'll go into OL, and I don't want to cook anything.

I've been told time and time again to take the bias reading between 1/8 and chassis ground.

Oops,

Forgive my ignorance. I meant the screen grid resistors, or at least the ones tied to pin 4.

Ok, been super busy at work, but was finally able to get a better look inside. When I went to check the value of the GBR's, I noticed that three were unsoldered on one side. I'm guessing the amp got that hot. I unsoldered the fourth one and checked the resistance across all of them which all read 1K...

I took a reading on either side of that big grey resistor connected to pins 1 and 8 and had a 100+mV reading on the third tube (the one that was red plating). I used the bias pot to get it to around 35mV, but when I went to read the others I get a 0 reading. Thought I had no problem getting a readin...

FYI, I'm trying to set the tubes (which are 4 EL34's in a 120 watt amp) to 35mA. The Weber bias calculator sets this at hot with the plate voltage at 500VDC, of which I'm reading 510. The Matamps are known for running hot and power tube breakup is a huge part of their sound, but I wouldn't want to h...

And thanks for the welcome and help, guys. I can see myself coming here as often as possible. It's also reminding me that I need some basic electrical classes, lol.

[IMG:640:478]http://i36.photobucket.com/albums/e7/Muzikazoo/IMG_1117.jpg[/img] Maybe this pic will help. The tube placement indicator is pointing straight down at 6 o'clock, and I was led to believe pins 1 and 8 are on either side of the indicator, and that the numbers progress in a clockwise motion...

Hi, I'm very new to biasing my own amp. I'm aware of the dangerous voltages present inside and have taken precautions. I do work with electricity on a daily basis, just not inside tube amplifiers (just running my disclaimer). Here's the problem, I had one of my EL34's starting to redplate. I contact...