Pf50t rattling noise?

[jlt5x]

Update - I swapped out power tubes and problem solved. Slight rattle in old tubes. They Still work - probably could create some type of buffer to suppress vibrations, but this was easy and still sounds great.
Thanks all

 

[cooks33]

Reviving this old thread...

I'm having a similar issue with my power tubes. The amp was making a resonance/buzzing sound with certain notes with my old set of power tubes. A few months ago, one of them burned out, so I bought a new set of matched power tubes (JJs from TubeDepot). Noticed the buzzing again. Today, I took off the spring tube retainers, but the buzzing persisted. When I tap the power tubes I get the same rattling/buzzing sound. When I tap the preamp tubes, nothing. Does this mean the power tubes are microphonic? Kinda frustrating this these are brand new. Should I ask for a replacement set of tubes?

 

[jlt5x]

make sure the retainers are snug against the tubes. you may have to take out tubes and bend them in…. i have found times when certain tones make the tubes rattle but tight retainers help. i also use a foam pad under amp to help with cab vibrations

 

[beans-on-toast]

Reviving this old thread...

I'm having a similar issue with my power tubes. The amp was making a resonance/buzzing sound with certain notes with my old set of power tubes. A few months ago, one of them burned out, so I bought a new set of matched power tubes (JJs from TubeDepot). Noticed the buzzing again. Today, I took off the spring tube retainers, but the buzzing persisted. When I tap the power tubes I get the same rattling/buzzing sound. When I tap the preamp tubes, nothing. Does this mean the power tubes are microphonic? Kinda frustrating this these are brand new. Should I ask for a replacement set of tubes?

Based on your description, it sounds like there’s something loose within the tube. They are under warranty, you can contact TubeDepot and request another tested set.

There are mica spacers inside the tube, the ends of the mica are supposed to push up against the inside of the glass envelope. This lack of support can cause a rattle and the tube can be microphonic. Below is an example of bad mica spacers in a small signal tube. They should press firmly up against the glass and the tips actually bend. Visually inspect them and see.

There are other potential internal issues as well that can cause a rattle such as a broken weld or loose wire. This can be more difficult to see.

If one of your old power tubes is still working, you can swap it in, one position at a time and test to see if the rattle goes away. Just to be sure that it isn’t a tube cover issue, remove the preamp tube shields while testing. Also do not install the spring retainers over the power tubes.

If the spring retainer is rattling, it can help to slip some high temperature silicone tubing over the spring so that it doesn’t rattle against the glass. This is available at some hobby stores or amazon.

 

[bassicstu]

My Pf50t sounds awesome. Bias lights are green, and flash red when I play.

But when the head is bumped or shook, there is a rattling like noise that actually comes through the speaker. Not super loud, but it is there. Happens if I tap on the head or even when I play a low e.

Haven’t tried to reseat the tubes yet - just figured I would see if anyone else has experienced this.

tia

My head had/has the same rattle. I tried tapping things when the amp was off because it made no sense to me that the rattle was inside the tubes. I never heard a rattle with the amp off. Turned the amp on and 2 tubes rattled when I tapped on them. One power tube and one preamp tube. (Power tubes are the big ones and pre amp tubes....) Swapped the Power tubes with a pair I had in my desk. Doesn't every one have a spare set of power in their desk drawer? LOL No rattle from the power tubes. Swapped the location of the the 12ax7a preamp tubes. The tube with the rattle still rattled. Looks like Ampeg had/has a crappy tube supplier.