New white noise in .50 Cal clean channel

[HockeyMike]

I've got a .50 Caliber that I've owned since 1988. I just performed a new retube, popped in some TungSol 12AX7s and JJ Tesla EL84s (instead of previous Sovteks and Boogies), and while the tone is great, there's some white noise now in the clean channel...sounds like the ocean, where it used to be dead quiet. I thought there might be something wrong with one of the new tubes, but when I put the old tubes back in, the white noise is still there. Switched back to the new tubes, swapped positions around a few times, no better. With nothing plugged into the amp, the clean channel is actually noisier than the lead channel.

Could the different tubes have had some kind of effect on a dying cap or something? Any other ideas?

Thanks,
Mike

 

[sander78]

perhaps some bad connection in the socket..
perhaps you could try to clean it with for example some kind of contact spray.

 

[HockeyMike]

I had sprayed an old tube with DeOxit and ran it through all the sockets before installing the new tubes, and after the noise appeared I removed the tubes again and gave everything a quick shot of compressed air in case some speck of something had gotten lodged inside...noise is still there.

 

[stokes]

Starting with tube #1,pull it out and if the noise is gone your problem is there.If the noise is still there put it back and pull #2 and continue down the line till the noise stops.When it stops that is the stage the noise is coming from.Now try different tubes in that location,but first make sure the socket is clean and the tube pins are clean,and retension the socket.A loose socket could cause the noise.

 

[HockeyMike]

Thanks, I'll try that.

I did notice that the pins on the JJ EL84s are a hair smaller in diameter compared to the Boogie ones...the sockets don't "grab" them as tightly.

I'm new to socket retensioning...how is that done? Should I do all 4?

Thanks,
Mike

 

[stokes]

I've heard this about the JJ tubes.To retension the sockets you should first be sure the filter caps are drained,or you could get shocked when you touch certain pins.I use a dental pick to do the procedure.Just pull the tubes and carefully use the pick to squeeze the openigs for the pins tighter.When using a cleaner I wouldnt use an old tube,but use the tube you are putting in.Even a "new" tube can have some oxidation on the pins from sitting on the shelf.

 

[HockeyMike]

Thanks for the info. Just one more thing...how do I make sure the filter caps are drained? (This is all new to me...)

 

[stokes]

You have to open the chassis and physically drain the filter caps.I use two aligator clips with a 470 ohm 2 watt resistor wired between them. Connect one end to ground and one end to the + terminal of the main cap.Be careful there is dangerously high voltage here.