Full Re-Tube..HELP, knowledge NEEDED!

My current tube complement:
Preamp: 6x 12ax7’s
Power: 2x EL34’s
2x 6L6’s

As anyone who owns a tube amp knows: when the tubes start to go you start to worry:

So I did a little research

Here: http://thetubestore.com
and here: http://analogtubes.com/tubeshop/

And some other places and found that if you’re willing to spend the time, money and brain power, playing with your tubes can be very rewarding. Apparently next to restringing it’s one of the most substantial ways to change your tone.
The problem I have had is that many people I’ve spoken to about tubes seem to emit this strange odor that smells suspiciously like the back end of a bull when they open their mouths… I want cold hard facts: telling me that groove tubes sound a bit like a vanilla fudge milkshake tastes does not further my knowledge of the situation it only makes me want a milkshake.

Quick Q&A on what I found out:

Q. How much is this going to cost?
A. This depends on a verity of factors but a full re-tube could run you anything from $100 to way more than $100.

Q. Will I be able to replace the tubes myself?
A. Maybe: do you have a voltmeter and know how to use it?

Q. What is biasing?
A. Biasing basically means optimizing the voltage to stop the tube overheating (causing melty, explody, bad times) or running cold (causing general lameness and an inability to get that high gain tube tone you want)

Q. What brand of tubes should I go for?
A. Phhh, this is a tough one. I’ll have to get back to you after rigorous testing.

Q. Why doesn’t anyone I speak to seem to know anything about tubes?
A. because there is so much hearsay and conjecture surrounding tubes that most people simply give up and end up sending there amp out to some retail store like guitar center who in turn ship your amp out to some mystical realm where a counsel of elder consult with mighty wizards known as technicians who cast magical spells and remove the eyes from dragons which are then forged into your new tubes through methods lost to the rest of the modern world. The problem with this is it takes a long time and its almost as expensive as buying a new amp… (Wizard’s and dragon eyes don’t come cheap)


If any of you guys have legitimate knowledge and experience regarding tube replacement and tube characteristics I would really like to hear from you. I’m looking at things like: build quality, longevity, Harmonic response (microphonics), noise (hiss, pop, hum) .

I need to re-tube ASAP because this hum is steadily getting worse as my tone gets less crunch and my sustain becomes nonexistent... HELP

I hate to comment when I really got nothing, but these guys helped me choose some tubes to re-tube my amp with... http://www.torresengineering.com/maprtutse.html . I used Mullards.

There are too many combinations to figure out yourself. I think you gotta find someone who sells a ton of tubes you can talk to.


http://www.torresengineering.com/gu1megpottrt.html

Harley,
Lets start with the amp. Make and model please. sometimes you can find specific info from an "expert" on your model as I did with my fender blues jr amp. there's a guy out there who is a legend when it comes to the blues jr and all the mods etc. His name is BillM. Anyway, you may be able to find good recommendations for your amp. meanwhile here is a topic I posted a long time ago. Take a look at it and follow the links. You may find them illuminating.

http://www.all-guitar-chords.com/topic.php?id=3155

Phip

finding a shop that has a tube tester would be a handy thing. make some calls. testing the tubes my lead you to one or two that have shorts or extreme leakage.

All of my amps are solid state,so i dont lnow
too much about tubes.But id reccomend you buy
one of these bias king tube testers.They will save you hundreds
in the long run and allow you to check the status
if your tubes yourself to see if they need
replacement.

http://biasking.com/

^^^link to site.

\M/(*-+)
gs2112

thanks for the input guys.

@Phip: its an Egnater Renegade 65w 2x12 combo

Is it really necessary to purchase a tube tester? Im rarely going to use it and cant I do essential the same thing with a voltmeter?

I didnt say it was necessary,i just reccomended it.
Its pretty good thing to have around,espicially if you
own a tube amp.Amd the voltmeter just gives you voltage
,the tube tester(bias king) gives you a printout of the
exact specs needed to keep your tubes bias correct to
know when to change em.But i guess if you know
how to adjust tubes based on what the voltmeter
says,then no,i wouldnt buy one.Its up too you.

\M/(*-+)
gs2112

Hey Harley,
Ok I just downloaded your user manual. I'll read that later.
No, you don't need to buy a tube tester. Whoever does amp repair in your town will have one and most places like that will let you use it to test your tubes. A tester will tell you if you have a shorted or horribly leaky tube. Why replace all your tubes if you only need one? So, you're going to have your tubes tested to find out which one(s) have failed. A few pointers or suggestions. Make a simple diagram of the tube layout before removing any tubes. Draw a rectangle and then circles where the tubes are located. I usually make small circles for the small tubes and large circles for the output tubes. Now assign a number for each tube and mark the diagram. example 1-10 (you can include the actual tube number if you want but it is not necessary. what you want is to know exactly which tube came from which socket). As you take each tube out one at a time just use a marker to write the correct number on each tube WITHOUT WRITING OVER ANY FACTORY MARKINGS ON THE TUBES. When you get home you'll be able to put the tubes back exactly where they came from. (since you have 6 12AX7's it would be nice to put each one back where it came from since each one differs slightly and affects the sound you have come to know). Be careful not to rub off any factory marking with your fingers. Now take your bag of tubes to the store with the tester and check them all. Ask for help if you don't understand the tester functions.
That's "tube testing 101 for beginners". I need coffee, then i'll come back and continue. ;)
Phip

ok, I'm back. Where was I?
oh yeah, so, the reason i suggest putting your tubes back exactly where they came from is because if you take 6 12AX7's and test them, they will all have slightly different characteristics. By putting them back where they were originally you won't add to your diagnostic frustrations. Ok, now, after testing your tubes you may have one or more bad tubes. If you are replacing the small 12AX7's there is no need to "match" or "pair" them. Got one bad one? BUY ONE! However if you need one EL34 or 6L6 I would strongly recommend replacing those as pairs because they work together in producing power. If you put one new strong EL34 in with an older weakened EL34 you are likely to have problems like a short life for the pair or distortion problems. The Power tubes IMO should be matched.
Phip

OK, now lets talk about bias. I'll give you the basics.
just as your water faucet can be set to produce a small stream or a powerful output of water by turning the knob, your tubes act much in the same way. Volume and Gain controls determine how hard the tubes will work. Bias sets the parameters by which the tube performs at rest. By adjusting the voltage to a control grid within the tube you control it's current flow. Bias is used to set the "cut off" point of the tube so that when no signal is applied the tube "cuts off" and makes no noise or static. In a less direct way it also sets the tube so that under optimal conditions the tube does not overdrive and distort your output signal. Too little flow through the tube and you lack power, too much and you risk clipping and distortion where you don't WANT distortion. Too much flow also leads to short tube life. Good amps allow you to adjust that control grid voltage. This enables longer tube life and better fidelity. Adjusting is easy enough if you are not afraid of electricity. (some people are, and to a certain extent you should be cautious around electric circuits). My recommendation is to unplug the amp and get in there and identify the bias controls, look them over, try getting your hand and screwdriver in there without bumping hot tubes or bare connections. Get comfy with having your hand in the tiger's mouth BEFORE you plug it in and stick your hand in there ok? OK
Get the specks and adjustment instructions and you are ready to adjust the voltage.
you'll need an inexpensive volt meter. May i suggest a meter that reads AC DC volts and resistance too. You will find it to be a handy addition to your tool set. Don't buy the most expensive. Don't buy the cheapest. Go to Radio shack and pick the mid-priced model. I have a Fluke meter, cost me about 450.00. You don't need anything that elaborate. I do this for a living so i need good tools. You should be able to get a reasonable meter for 20.00.
Look at this one
http://www.radioshack.com/search/index.jsp?kwCatId=&kw=vom&origkw=VOM&sr=1
While you are at the store pick up a good jumper lead with alligator clips on each end. You'll use this to jump the black lead from the meter to ground. This will leave your hand free for other things. You want a jumper with a good piece of wire. nothing too skimpy. You'll set the meter for DC volts and put the red lead where the instructions tell you to. (practice this while the amp is cold and unplugged) Most meters nowadays will self adjust for the voltage range you are reading so it's going to be a piece of cake. You'll read the meter and very slowly adjust the voltage to specs AFTER letting the amp warm up for 10 minutes. Do the job and then get the hell out of there!
As far as what brand of tubes to buy.......I have no idea. Just being honest here. Everyone is going to tell you how great their tubes are. You'd have to buy every damn brand out there to really know for sure. Once again I suppose it is wise not to buy the cheapest OR the most expensive. Ask friends, ask musicians. DON"T ask sales people.
More questions? Ask
hope this helps you Harley
Phip

Phip-
but do you know anything about tubes and biasing and...oh, it seems like you do:>

Phip

Thanks man I really appreciate you taking the time to explain in detail. ill be referring back to this when the new tubes get here.

I decided to order a full compliment. went with Tung sols all round. (after sifting through a bunch of reviews they sound like they preform well)

This way I can test the old ones and ill have them as backups if Im ever in a pinch.

I do have one other question:
what is a phase inverter tube?

Harley,
When an amplifier uses a push/pull output stage (two matched tubes) it requires the audio signal to be "inverted" when it reaches those output tubes. What this means is that the signal is duplicated but inverted so that two identical but opposite signals arrive at the output stage to drive the output tubes. think of it like a seesaw. one signal is rising while the other is falling. by using this technology the output stage works less hard and extends the life of those output tubes. this also has a side benefit of eliminating stray static and unwanted distortions by canceling them out. There is nothing special about the tube itself. The 12AX7 can be used to perform this function (and probably does in your amp). The trick is how the inverter tube is wired.
For a more detailed look at how these tubes work you can read this

http://www.300guitars.com/articles/article-demystifying-the-phase-inverter/
Phip

Dang Phip, this is some really great knowledge you just shared with us all. Thanks!!

ok so the new tubes were installed and biased.
worked for a day or two then out of nowhere most of the volume dropped out on the gain channel of my amp!
I don't think (or dont want to think) its any of the power tubes because the clean channel seems to be functioning just fine.
if it was one set of power tubes wouldnt i hear a difference when moving the tube blend from 6L6 to EL34 on both channels...?

all the tubes are still glowing when switched on,
no tubes show discoloration.
the fuses for each pair of power tubes don't appear to be blown.
strangely the gain boost switch on my amps foot pedal seem to boost me back up to a normal level...

Oh mighty Phip,.. Im pulling my hair out over here, did I just blow a brand new set of tubes?

Harley,
You're saying that channel 2 is screwed up?
If so, disconnect that foot switch temporarily and then set both channels exactly the same (gain, tube mix, volume etc) and switch between the two channels to see if they sound the same.
First thing we want to know is if the amp performs properly on ch1 and ch2 WITHOUT the foot pedal.
Let me know.
Phip

channel 2 is most defiantly screwed up, with and without the footswitch.

usually with all the settings at 12o'clock and the master volume at 9:00 this thing roars... right now It sounds like someone playing guitar way off in the distance.

hmmmm ok
I have the owners manual but not a wiring diagram (schematic). I've been searching the net but so far....nada.
So.......hopefully you still have the old tubes laying around. I want you to take out the two new 12AX7's CLOSEST TO THE OUTPUT tubes and put two old 12AX7's in. be sure to keep track of the two new ones you are taking out. let's not get them mixed up.
Try that
If there is NO positive change, put the new ones right back in. Then do the same thing with the next 12AX7's in the chain. be sure you test ch1 AND ch2 each time you do this.
(forget about the output tubes for now because I don't think your problem is there.)

of course Phiplock Holmes, process of elimination, its elementary.
ill be trying this tomorrow.
I had no luck finding a schematic diagram either but I think I may have dug up Bruce Egnaters personal email so maybe if i ask nice enough he will send a copy to me.
once again thanks muchly for your help, ill let you know how i get on.

Ok so it was indeed preamp tube number 4 (had a faint black ring at the bottom)

so i threw the old tube back in there and lo and behold this was the source of the original humming/fizzling problem.

the only conclusion i can draw is pre tube number 4 is getting fed just a little to much juice causing the original tube to hiss and the replacement to blow.

i did manage to find a functioning tube from the old set and throw it in there but now i really have no idea which tube started off where...

Don't jump to conclusions. Obviously the original tube was bad but probably died of old age. The new tube could be a dud. Only way to know is to run it with the "new old tube" in there and see how it performs. If everything is still good after a week or two you can send the new tube back (depending on the warranty). Now a note........a black blob or dark area on a tube is normal. I'll explain.
These tubes are vacuum tubes (no air). The way they get the air out of the tube is done by igniting a "getter" in the tube after it is assembled to burn off the remaining oxygen. This process causes a "burn mark" on the glass, black, sometimes silvery.
Ya learned something today!
Phip
Glad the amp is working again. Keep me posted.