Time for my first re-tube

[gtrjunior]

I’ve been jamming with a new project with some friends friends lately. Last Saturday I went downstairs to play/review some songs i was learning for a rehearsal later that day. I turned on the amp, in standby to let it warm up a bit and when I switched it into play mode I blew a fuse! Off to the store I went and grabbed some fuses. I replaced to blown fuse and tried again....popped it again!!
Only this time I saw a bright flash coming from at least one of the power tubes. Obviously that scared the crap out of me. I emailed Scott and explained the situation.
He basically said that when a tube blows it’s normal for the fuse to also blow....it’s doing what it is supposed to do...protect the circuit.
I installed another fuse and powered the amp on in standby mode again....it indeed powered on but I didn’t dare take it off standby.
I ordered a set of tubes from Scott today. I’ll get them installed and biased up as soon as they arrive.
I got almost 2 years out of the original tubes. Not a bad run. I guess I have nothing to complain about.
I’ve never had a tube blow like that before! In my Marshall the amp always gives me signs that it’s time to change tubes....I didn’t get any warning this time.

[cvogue]

Yikes! That's kinda scary... I've never had a power tube blow. Blew the PI tube in my old Peavey Ultra 120+ but only noticed that it impacted the sound...

How often did you use the amp? i.e. how many hours did you have on the power tubes?

Wonder if the beefy transformers that Scott uses could be harder on the tubes. Pure ignorant speculation on my part!

[gtrjunior]

I use it several times per week. Maybe, all together about 6 hours per week. I have it set up in the basement where I can turn it up a bit so I push it a little when I can.

I wonder how it works with the loop volume? Since we can turn the front panel volume up and use the loop volume to bring down the overall volume.....I’m sure the amp still “sees” that as being pushed pretty hard...?

[briman]

My 2015 QR still has the original tubes in it. I don't use it as often as you though because i have the 2016 in basement which also has original tubes.

I once had a brand new tube blow in my Competion right after installing it! It litetally made a pop noise through the speakers and then lit up bright bright red. Fuse didn't blow but i had shut it off about 5 seconds after pop.

I have been very happy this week as i have run my amps through grounded outlets and there is zero buzz! I don't even need a noise suppressor with the 2016!

[splawndude]

Seems quick to me.

What tubes were they again? Not that Chinese stuff I hope.

I've never had a power tube blow. I don't gig regularly like some of you though. Hell, I still have the original Mullards that were in there when I got it. Never seen a power tube pop like that but it does happen. Hopefully it is not indicative of any other issue.

Sorry - I should probably know, but I'm assuming you have back up power tubes. Are you going to go ahead and get new power tubes as well? If so what. I highly recommend The Valve Queen but hear lately she is slow to ship/respond.

Also, I doubt the size of the output transfer or the loop volume is going to put any undue stress on power tubes.

A poor bias, mismatched tubes, a bad phase inverter tube, running without a load/mismatched load, crappy grid resistor, poorly seated tube, socket arc'ing, etc are far worse IMO.

[gtrjunior]

These were the stock tubes from Splawn.
I just reordered a set from Scott yesterday.
I don’t mind another/better brand but I’ve read several posts where people have talked about buying a set of tubes from another retailer and then the tubes won’t bias up without replacing a resistor or something....
I just figured it’s easier to get the same number tube from Scott.

As far as the length of service for this set...
When I biased these tubes shortly after I got the amp, I set the bias slightly hot. Iirc, the formula called for a 32mA bias and I went with 35mA. So, really just slightly higher.
With my Marshall, when I was gigging regularly I was replacing tubes about once a year. That amp never blew a tube. It always gave me signs ahead of time that they needed changing. I would hear popping noises that would slowly increase in frequency over several weeks. Follows by volume fluctuations.
Even though I’ve only gigged this amp a few times I have played it a lot over the last 2 years. I’m not all that concerned with how long the tubes lasted but I am a little concerned that another component might be damaged. Hopefully not. The fuse did what it was supposed to do so I’m hopeful that everything is fine.
Funny thing is that none of the tubes had any visible damage or other sign of tube failure...still that doesn’t necessarily mean anything. A tube can fail and not have any visible damage.

[gtrjunior]

Just email the Valve Queen. I’m curious as to what she recommends.
I saw on the website that JJ has some 6CA7’s now....I’m intrigued.

[briman]

I used to put Electro Harmonix in my Competition and they sounded awesome and i had no prob biasing them.

Like Splawndude, I was surprised yours went already also but i didn't know you had re-biased it since receiving it from Scott. 35 is a little on hot side so hopefully that is what wore them down and not something else more costly.

[gtrjunior]

I just looked at my tube stash and found a set of reissue Mullard. I had bought these when I had my JVM. I suppose I could throw these in on Saturday and see what happens.

[gtrjunior]

splawndude
briman

I’m a little surprised that you find a set of tubes that lasted almost 2 years to be a short life span.
From what I’ve read online and my own experience, an amp that gets regular use usually gets a retube about once a year...?

[briman]

My 2015 QR has had about 2 hours use a week for 2 years average and the first year about 6 or more and still sounds like new.

I recently heard an amp tech say that he has seen amps come in from the 70's with original tubes and sounds like new. He said if an amp is properly biased and maintained, quality tubes last a very long time.

But he did say that tubes are not as well made today and there are brands that will last just over a year. I think he mentioned chinese for that part.

I had to change marshall tubes that were original in a dsl once after 2 years and i changed my tubes in my comp after 7 years and it sounded a bit more articulate but not a huge difference.

So i hear different opinions and views on a tubes lifespan. Now i only change if my amp starts to sound dark and loses its edge......like sharpening my skates lol.

[briman]

Gtrjunior ďid Scott mention anything about your 35ma bias setting being a little hot?
I would think maybe bring it down to 28 to 32 somewhere. My buddy says he found his Splawn to sound better biased on colder side but this is subjective to taste of guitarist. A SPLAWN is already hot rodded so i wouldn't go higher lol.

I am no expert though and have biased my amps about 5 times. I think Splawndude is very knowledgeable in the tube bias topic.

[gtrjunior]

I didn’t mention he bias to Scott. But I think you’re right, I’m going to set it to whatever the formula comes out as.

When I first got my amp, I was having these volume fluctuations happening. I checked the bias and it was cold. Iirc, somewhere around 25mA. Once I raised it the issue went away. But I agree that 35 is probably a bit too hot.

[gtrjunior]

Even though I just bought a new set from Scott, I just ordered a set of JJ 6CA7 from the tube store too.
splawndude....
A 6CA7 is rated at 25w just like an EL34....right?

So I still use 25 when I’m working through the bias formula?

[cvogue]

gtrjunior the tube buying maniac!!

Let us know how it all turns out.