Post by goldenexits on Oct 28, 2017 16:06:31 GMT -7
So I am having this issue where the amp makes a terrible screeching sound if i turn up the EQ, Pre, or post volumes. I have already tried swapping out each of the preamp tubes and power tubes. I have also tried unplugging the reverb and have swapped out the speaker cable. I recorded it to show what is happening. Any ideas of additional things to check?
It does this with or without the airbrake. It also still makes the sound when nothing is plugged into the input. What's interesting is the sound changes depending on how the EQ is set. You can hear how it changes at the end of the video.
Post by Jaguarguy (Mike) on Oct 28, 2017 16:25:15 GMT -7
Welcome to the Forum! A lot of good info and people here! Here is a link to the troubleshooting page of Z Amps. Hopefully this helps you isolate the issue. Did you try to replace the rectifier tube? That's where Doc starts his trouble shooting process. Hopefully we can help you get it back up and running for you!
Post by Chilly Gibbons (Todd T.) on Oct 28, 2017 19:53:49 GMT -7
Something is causing the amp to oscillate when you increase signal level beyond a certain point, with either the eq or the gains. It really sounds like a preamp tube as they drive both the gains and tonestack. I realize you’ve checked them, but the preamp is most likely where the problem is, not the power section. Did it just start doing this? Are your preamp tubes shielded? With the amp on and oscillating, I would gently rock each preamp tube in its socket in a circular motion, being careful not to remove it to see if there is a connection issue with one of the sockets. If it stops oscillating, then Possibly one of the pin connections needs tightening. It’s unlikely that there any issues in the chassis like cold solder joints or shorting. Hope this helps.
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Post by jordanbunte on Aug 13, 2018 12:07:10 GMT -7
Go back into the EZG-50 pages and you'll find some threads about it. Seems like HQ was repairing these affected heads at one time (without charge). Not sure if that offer still stands. It was a long time ago.
Last Edit: Aug 13, 2018 12:08:33 GMT -7 by jordanbunte
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