Tube going out?

[Darrick]

I have a 2 channel h combo and its making intermittent crunchy echo-y fuzzy noises. I found a thread here of someone else having similar probs and the thought was that possibly a preamp tube 'went harmonic' or something like that. Have been trying to find that thread.
I actually just got it a month ago so could send it back, but already had the mail system thrash one to the point it didn't work so returned it and this is its replacement. I do trust PRS but NOT the mail system. I will plan to get fixed locally but seeking knowledge/ advice on problem and also need schematics.
Help?

 

[11top]

I had a similar problem on my 2 channel custom. I changed a bad preamp tube and all is right with the world (well almost).

 

[prscat33511]

can you try swapping a preamp tube?
Tap lightly with a pencil eraser or a chopstick
Maybe the tube is not seated properly due to abusive shipping procedures from the carrier ?

BE CAREFUL - tube amps have lethal voltages and could hurt you in a bad way, tubes get hot also
Dont try this if you are unfamiliar or unexperienced in this procedure

 

[Ron]

Yes, I had a preamp tube go out in my 2 Channel H combo a while back. That may have been my thread you read in the amplifier forum. I replaced all five preamp tubes with JJ's and it's singing again! There is one other tube that drives the reverb (the 12DW7 near the power transformer) that I did not replace. Word here on the forum was that it was probably not the culprit. I did not replace the power tubes either, but I found it helpful to remove them to get to the preamp tubes behind them. Removing and replacing the sleeves of the tubes near the reverb housing is a bit tricky, but just take it slow. Good luck!