Tried swapping preamp tube positions as a 'last resort' fix and it actually worked

I had this Fender Princeton clone I built last winter that started making this weird humming noise after about 3 months. I checked every solder joint with my magnifying lamp, swapped the filter caps, even reflowed the whole power section. Nothing. I was about to rip out the whole board when my buddy at the guitar shop said try swapping V1 and V2 tubes. I thought it was a joke but figured why not. Took me 30 seconds and the hum dropped by like 80%. Apparently one of my new JJ tubes had a microphonic issue right out of the box. Has anyone else had new production tubes that were duds like this?

2 comments

2 Comments

wrenwilson3d ago

Read a luthier blog that said modern tube QC is basically a dice roll, especially with JJs. Had a matched pair of 6V6s that were noisy from day one.

mason3613d agoOG Member

My condolences @wrenwilson, bad tubes are a real pain to troubleshoot.

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