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Help Diagnose Tube Preamp Problem

I have a George Wright preamp along with his mono 3.5 amps. I recently started hearing some noise or crackling through my speakers at various times. When I turned the system on the other day, it was very loud for a couple of seconds, but then went away. I've done some research and "tested" the tubes by gently tapping them with a pencil, and the weird thing is the tubes in the preamp all give off a ping that is not solid like the tubes in the amps (I don't believe the tubes in the preamp all went bad at one time). Even stranger, if I tap on the metal on/off switch, this also pings through the speaker as if it is somehow getting picked up by the current. Something strange going on, anyone with any ideas of the problem? thanks
skf3636
opus88
530 posts
 
No one's necessarily leading him astray. I certainly agree with what you say about pinging sounds being heard routinely when one taps on preamp tubes, but crackling or ripping noises that come and go is fairly symptomatic of a problem with an amp's output tube(s). On the other hand, a troubled or overly stressed preamp tube usually sounds almost like one very gently clearing his throat or a high pitched eeeee sound. At least this has been my experience on a number of occasions.
jea48
4,449 posts
 
Skf3636,

Both channels or only in one?

Could be a dirty and or corroded tube socket/s or tube pins.

Quick method of cleaning is to unplug and reinsert tube/s in socket several time to clean the pins and socket contacts....
skf3636 OP
7 posts
 
Thanks for the responses. I'll try the quick method of cleaning the tubes/sockets. Both channels are affected. I'll also get the tubes checked at a local shop if I can't get it working properly.
jea48
4,449 posts
 
Both channels are affected.

Skf3636,

Both channels?...... Have a feeling it is something in the power supply. Could be a loose connection. Maybe a cold solder joint.
atmasphere's avatar
atmasphere
11,841 posts
 
Sometimes AC power switches can develop issues that will cause crackling. This is caused by bad contacts in the switch. Tapping on the switch can sometimes excite the behavior.

If you get a pinging sound by tapping on the switch, it is because vibration is transmitted from the switch to the tubes through the chassis.
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