Tube Amp Archive

Here is an update. I replaced the .047 capacitor feeding the grid on the suspect tube socket. The amp is working great now! My grid and plate voltages are perfect giving me very near 70% plate dissipation. One clarification is that I do have the 2000 pf caps on the grid to ground. They were mounted ...

Thanks to all for your help. I've order some caps and will update when I change one out. All resistors are in spec.

First, pull the 6L6s and set aside. Now measure the negative voltage on pin 5 of each 6L6. What have you? Looking for two numbers. If they are not about equal then... I like to unsolder the cap leg that connects to the 6L6s. Then recheck the negative voltage on pin 5 of each tube. If about equal, t...

First, pull the 6L6s and set aside. Now measure the negative voltage on pin 5 of each 6L6. What have you? Looking for two numbers. If they are not about equal then... I like to unsolder the cap leg that connects to the 6L6s. Then recheck the negative voltage on pin 5 of each tube. If about equal, t...

sluckey wrote: ↑Wed Feb 03, 2021 8:57 pm Disconnect the .047 coupling caps first. Any better?

Don't know what you mean by disconnect? Unsolder leg? If so which leg, near the tube socket, or the bias pot?

I have a '74 Bassman, circuit AA371 with a bias balance pot. One tube is reading 42Ma and the other is 64Ma. Trying different 6L6GC tubes it seems to be consistent with the tube socket not the tube. Any suggestions on where to troubleshoot the socket or bias circuit?

I fired up my '66 Twin Reverb for the first time in months. The tremolo roach is working because I can hear a ticking, but the tremolo effect is barely noticeable. However, the interesting thing is that when I turn my intensity knob down there is a corresponding volume increase in the amp. When the ...

I recently purchased a blue esr meter to test capacitors. It works great in circuit. If you go to youtube and check out Uncle Doug channel he has a recent demonstration of the meter and explains how it works fine in circuit.

Update: Thanks for all of the suggestions. I was getting ready to test the wires coming from the voice coil and noticed a very tiny tear, like a flaking of the paper cone near where the wires connect. As I pushed on this little flake to press it against the cone the entire cone raised exposing a com...

Lots of theory in the comments. I wouldn't argue with safety first. However, for the more practical minded do this experiment. Google this topic and let me know if you find a single instance of a person stating that they actually fried a voice coil using a 9v battery. Not hearsay, but actual first h...

@ampdoc1- I appreciate this website, because it is a valuable source of information when I come across a problem that I'm not familiar with. I've never experienced a blown speaker before, although I've changed out and checked the phase on many. I appreciate your input concerning the ohm reading. How...

@ampdoc1- You may be right about the ohm reading of a blown speaker, however I doubt your concern about the use of a battery is valid. I have seen many amp and speaker techs on youtube recommend the use of a battery to test speaker phase. This includes Gerald Webber. I have never heard of a warning ...

I recently purchased a pair of 1961 Jensen speakers. Have been testing them and noticed that one wasn't making any sound. Took it out of the cabinet and tried to test the leads. I can get no movement of the cone when applying a charge from a battery. Also, my multimeter indicates no ohm reading at a...

I've been tracking down the source of a rustling static in a '67 Super Reverb for a couple of months. Finally, after re-soldering the eyelet of the # 2 pin (grid) of the PI the rustling stopped, and all appeared fixed. I have no idea why, because I replaced that 1M resistor and took care in my solde...

I have a question for those of you more knowledgeable on the subject. I don't own a tube tester, but have been wanting to find a way to compare the sound of 6L6's to select the best ones. And even to try and identify poor tubes. Is it safe on the amp to operate it (push/pull) with just one power tub...