Diagnosing Help Needed Bad Tubes or RFI

[Danno]

So my Fender Champion 600 I bought used in September came with NOS tubes not the factory originals. It started making noise a few weeks ago.

I tried the pencil test and I think the 12ax7 is bad it barely glows as well. But the pencil test isn't the easiest when I don't have multiple of the same tube to compare.

I get some noise with nothing plugged in. I get more noise with a pedal and no guitar.

Link to 30 sec video:

New video by Dan Pugatch

photos.app.goo.gl

 

[LesB3]

I ran into some issues with my Superonic 22 yesterday as well. The link doesn't seem to work, so not sure if its the same issues I'm having or not.

A few days ago, it started to have a trailing hum any time I hit the low E string hard. Yesterday, it was "feeding back" even with no signal / guitar attached. Both are symptoms of bad tubes apparently, the former indicating a power tube, the latter indicating a preamp tube. I'll be doing the pencil test in a bit, haven't done that yet.

 

[Danno]

@LesB3 I just updated the link it should work now

 

[oneforsorrow]

Interested to see what happens with this post as I'm having a similar issue with my amp.

 

[LesB3]

@LesB3 I just updated the link it should work now

Huh! Definitely strange. Mine was different from that and I don't think yours has a bad tube. But not an expert either. I tried the pencil trick on my own amp but could not reproduce the issues from yesterday.

Do you have another boost you could try? TS etc? Have you cranked it w/o the pedal altogether?

 

[Danno]

Huh! Definitely strange. Mine was different from that and I don't think yours has a bad tube. But not an expert either. I tried the pencil trick on my own amp but could not reproduce the issues from yesterday.

Do you have another boost you could try? TS etc? Have you cranked it w/o the pedal altogether?

Only pedal I got, didn't make the noise for 3 weeks of owning/using the pedal with the amp.

Can't really hear the noise over the phone video but it's there just fainter with no pedals.

The 12ax7 doesn't really glow which is why I thought tube issue. It flashes once when turning the amp on... Didn't want to drop $$ on tubes if I didn't have to. I want Tungsols.and it would be 80ish to replace em.

 

[LesB3]

I guess the good thing is that you only have 3 tubes to worry about. Might just be easier to replace them all and be done with it.

Is the Milkman battery powered or plugged in? Do you have another amp to try the pedal with (just to rule it out)?

 

[Danno]

I guess the good thing is that you only have 3 tubes to worry about. Might just be easier to replace them all and be done with it.

Is the Milkman battery powered or plugged in? Do you have another amp to try the pedal with (just to rule it out)?

JHS Milkman is plugged into a power supply (Dunlop).
My only amp and my only pedal.

I'll try a different room (to rule out the wall outlet) and NOT user a power strip.

Yeah I may just go out and buy a 12AX7 and a 6V6 (rectifier is solid state). Already in my cart with Viva Tubes was ready to press Pay but wanted everyone's thoughts first.

 

[LesB3]

Sorry man, that's a real mystery. I don't know how often rectifier tubes fail, but you might want to replace that one too, while you're in there.

 

[J Bird]

If you pull a preamp tube, does the bad noise go away? If yes, then it's probably a bad tube. Otherwise, without a spare set, it's going to be tough to diagnose at home. Even if the tubes are good, it's still good to have a back up set.

 

[Danno]

If you pull a preamp tube, does the bad noise go away? If yes, then it's probably a bad tube. Otherwise, without a spare set, it's going to be tough to diagnose at home. Even if the tubes are good, it's still good to have a back up set.

Great idea I'll give it a try tonight

 

[Danno]

I'll wait till I get home tonight to do JBird's suggestion but I think I'm gonna be buying more tubes (did I subconsciously just want an excuse to buy them...) It might just be marketing and I'm a sucker for good marketing. I'm leaning towards Tung-Sol for my 12ax7 (which I think it he bad tube) and 6v6 for that 50s Tweed Tone in my my old Champ.

Some more internet research found: https://killerrig.com/bad-preamp-tu...ommon issue with preamp,or bottom of the tube.

 

[J Bird]

I really like the Tung Sol 12ax7. You can't go wrong there.

At least it's just two tubes, compared with a Twin Reverb with ten!

 

[Emergence]

I have replacement tubes on hand for both of my amps. You never know when a tube will fail. They’re getting expensive to buy just to keep on hand and I’ve only had two failures in my life that made the amp unplayable, but better to keep good tubes on hand than buy whatever’s available from GC.

 

[Danno]

Got home pulled the preamp tube and all noise is gone. Usually it starts at volume 5 and gets worse from there. Tested without Delay, with Delay, and with Boost. None of that noise in the video from my original post. I think it's safe to blame the tube. Never seen a British one before.

Gonna order a Tung Sol.12ax7 and Tung Sol 6v6. Online seems they are better than JJs for Champs and last longer than EHs despite made in same factory I've never had a tube amp long enough to replace tubes so it's gonna be a journey in trying out things. I'll order a spare set in a month to keep on hand. Perhaps another brand as my backup set...

 

[JackNangle]

The video doesn’t sound like a bad valve to me, it sounds like the high pitch whine you get from digital stuff sometimes. Have you tried putting physical distance between your pedal, power supply and amp? I’m leaning towards the power supply for the pedal being the culprit at the moment. Just my opinion though obviously.
Thats a Mullard ECC83/12ax7, they’re very long lived and no new production valve can touch it in terms of tone or reliability. Again, in my opinion

 

[Danno]

Good to know, I'll give it a try and report back

 

[JackNangle]

Try physically unplugging the pedal power supply from the mains, they can create (or pick up) noise even when the pedal is switched off

 

[Danno]

The video doesn’t sound like a bad valve to me, it sounds like the high pitch whine you get from digital stuff sometimes. Have you tried putting physical distance between your pedal, power supply and amp? I’m leaning towards the power supply for the pedal being the culprit at the moment. Just my opinion though obviously.
Thats a Mullard ECC83/12ax7, they’re very long lived and no new production valve can touch it in terms of tone or reliability. Again, in my opinion

With pedal 10ft away I get the same noise. I was able to use the pedal on top of the amp for almost a month with no issue.

Thank you for identifying what to within the amp I definitely lucked out on the tubes the previous owner had in here. I bought the amp for $186 used at GC.

 

[JackNangle]

Ok, try diming the amp so you can clearly hear the noise, the unplugging the pedal power supply from the mains (not the pedal)
How bright the heater glows isn’t an indicator of performance by the way. That initial bright flash is characteristic of older British made valves, particularly Mullards