JJ's

[G.I.G.]

I got my JJ retube kit from Bob at Eurotubes on Friday and they sound great! Thanks for everyones's advice, I'm glad I went that route.

I have one concern though. I've noticed that I am getting a lot of hum in the clean channel (V1 position). I tried swapping out tubes but that did not change anything. On the inside of my amp it says "NOTE: Use SPAX7 (low noise) 12AX7 in V1, use tube sheild". Does this mean I need another kind of 12AX7 in that position or a low noise ECC83S (if there is such a thing)? I made sure to replace the sheilds on the preamp tubes and everything is seated properly.

Does anyone know why they are humming so bad on channel 1? I e-mailed Bob at Eurotubes a few days ago and havn't heard back. I have a gig on Friday so I ordered a JJ ECC83S with the "low noise and microphonics" test from Tube Depot to be sent FedEx Express so I can get it in time. Hopefully that solves my problem. If not I'll have to throw the old Sovtek back in and I don't want to do that.

 

[Brewski]

Do you have those metal shields that screw on over your pre amp tubes? They look sort of like little aluminum cans. I think that could be what they mean. Bob is usually good about getting back to you. Have you tried calling him to speed things up?

Try using one of the old tubes with some electrical connector cleaner and put it in and take it out a few times to try to clean the connectors. You may possibly have a bad connection due to dirt or corrosion.

Try the easy stuff first. Does the humming stop when you use the old tube? Was there any special description on the old V-1 tube?

Just trying to help.

 

[Slimey]

I had some humming after a re-tube from Bob.

I did some troubleshooting and narrowed it down to one the the preamp ECC83s. I emailed Bob and he replied within 24 hours and said he mailed me a new one. I got it in the mail a couple days later, swapped it out and no more hum, no problems.

I experienced what has been stated in many other threads here and elsewhere -- Bob at Eurotubes provides great service.

Bad preamp tubes are not that unusual. I'm sure he'll make no fuss replacing it with a new one. It is the holiday season -- maybe he's out of town for a few days. :?:

 

[G.I.G.]

Yeah, Bob is great, no doubt. I'm just in a bit of a crunch to get a new tube. I'll try calling him tomorrow. No worries.

I did replace the tube shields over the preamp tubes. I just didn't know if I need a special tube for the V1 position.

 

[Brewski]

Yeah, I agree with Slimey on Bob's service. It happened to me, although, it wasn't just a humming problem. It was actually crackling and cutting out. It happened on my Blues Junior and Bob replaced the tube right away.

I still think that I might have a diode issue on that amp, but am not sure. I bought it used, so I think that I inherited other problems that I've got to work out. But that's a story for some other thread.

Do any of the tubes make a lot of noise when you tap on them with either your finger or a pencil eraser? That might help you figure find a tube problem. I am not pretending to be an expert, but it's a place to start.

 

[Slimey]

FWIW, my troubleshooting method to find the hum was to swap out each 12ax7 for a known good one and see what I got. You can pull preamp tubes while the amp is on. You can also stick a 'bad' tube in the reverb spot and just not use the reverb. Tapping with a pencil or flicking with your finger will help find microphonic tubes. All preamp tubes are microphonic to some degree -- you want the one that is least microphonic in V1, as problems at this level are amplified along the rest of the circuit.

 

[G.I.G.]

I definitely pinned it down to the V1 position. I was at band practice tonight and when I plugged in, the hum on the clean channel was gone. I thought it may have been a bad outlet at my apartment. But after playing for about 15 minutes, the hum came back. It's like it's off or on, no in between. I tapped the shielding with my drummer's drum stick and it went away with one tap, then it came back and wouldn't go away even when I tapped it. I noticed what would trigger it is when I would put it on standby, it would go away. Then, as soon as I would switch between channel's, it would come back.

It's pretty bizarre but a new tube is on it's way. I don't want to swap it out with another tube I'm using because then I would have a bad tube in another position. It's just a little weird.

 

[Brewski]

Cool G.I.G. At least hopefully you have it isolated.

I hope your new tube comes in time for your show.

 

[G.I.G.]

Thanks Brewski. It should be here by Friday. If not, I can always throw in one of my old Sovteks in that position. Problem is I don't know which 12AX7 I pulled out of the V1 position. Oh well, I'll get it figured out.