TubeMeister 36 Combo - Anode Fuse Blown?

So I got a used TubeMeister 36 and the amp was working great but I heard replacing the tubes would upgrade it's tone. I put in three Tung Sol 12AX7's in the preamp which worked great (about a month ago). I ordered some used "Tested" Soviet Telam 6P41P tubes from the Ukraine, which I received today. Visually they looked fine, with no signs of damage nor tell tale failure signs. They weren't matched but to my understanding this is done to cancel humming. When I first turned it on I got sound, I played for around 10 seconds until I bended the high E at the 12th fret when the distortion sounded rather odd. I heard these tube's sounded interesting so I wasn't sure whether that was an issue or it's "new" tone... Until about 30 seconds later, the sound cut off and all four of the LED's on the back turned on.

Since then I tried some different Telam tubes, moved them around, put the old chinese tubes in, and nada. Not a peep. When I manual test, I get a series of even flashes followed by the diode second from the left flashing once.

What do?

So...  Oh Lateralus, what a tale of woe!  Who told you upgrading the valves would improve the amp's tone?  No wait, that is a stupid question, about 95% of the guitarists out there who all just "know" it does!  Sorry if that sounds a bit off.  I'm very sympathetic to your plight but you made the most basic mistake there.  You said "...the amp was working great" then you told us how you were made to feel unhappy with your setup because there was something that would be better if only you believed what someone else told you without checking it out properly.

Read the "Valve Swapping" thread on the GM36 forum, the advice you will find there stands the same for the TM series too.  Look at Page 5 post #122 onwards for info supplied by VoodooJeff re his Wathen cryogenic valves.  You will find that a huge proportion of the very experienced and more feet on the ground guitarists around who are more reliably objective in the way they assess what they hear will advise you that the tales you will be told of "a new amp" just by valve swapping are utter bollocks!  You get very subtle changes at best and these are only relevant in a studio or solitary environment where you are not playing alongside a drummer, bass and other guitarists or keyboards who mask any such subtleties.  Under those conditions the differences are inaudible.  Would you pay £120 for a 12AX7, or £150 for an EL84?  That's for a single valve!  That's what VoodooJeff is talking about with his Wathen setup.  Check their website and see.

It's the same with "magic tone capacitors".  It's a total and absolute myth, there is absolutely no difference that can be perceived by the human ear in our field.  it can be demonstrated to be a myth in a couple of ways but people WANT to believe there is a magic mojo path to get the ultimate amp even without considering anything about how it works.  And they want to be members of the priesthood which can give out the message about it and to be great in the eyes of all who hear.  And the ultimate amp is always a step or two along that magic yellow brick road with either those who would sell you the snake oil or those who have already bought it and can't face up to the truth of the Emperor's New Clothes guiding you along the way.

Another myth is, 12AT7, 12AU7, 12AX7, 12AY7 are all equivalents but with varying gain and can be swapped in and out of circuits as you please.  They are absolutely NOT!  They are totally different valve types intended for totally different tasks and every important aspect of any circuit using one will be screwed by putting in a different one.  The only safe substitute for a 12AX7/ECC83 is a 5751 which IS very close in all of its important parameters.  

At the end of the day there is no substitute for good engineering.  These are engineered products not things whisked out of the air by magic, and the results of applying them successfully depend on our objective use and analysis of those results.  Be very careful who you believe with these "common knowledge" areas, they seldom involve any real knowledge at all.

To your problem.  Take the amp to a tech and get him to check the anode fuse as you suggested.  It requires going into the lower compartment and there are LETHAL VOLTAGES in there at times.  I strongly advise you not to do this yourself unless you have a fair bit of experience working in crowded spaces with such high voltages, (I say again, LETHAL).  He can check for other signs of damage at the same time and get the amp up and running.  And for what it is worth, I would bin the idea of using those 6P41P valves which are a) an incorrect but "equivalent" type, b) old to an extent you don't know, c) from the Ukraine (???), d) tested (really?  Tested on what? To what standard?)  That valve type can't take high B+ supply voltages and the line voltage they would see in the H&K is high!

Reject the desire to fiddle needlessly just because the grass is always greener, you have seen where that can lead you.  Stick to EL84s and 12AX7s and just go for something solid, reliable and decent sounding like JJs.  You will be just as happy in the long run. But you won't be the last one to go down this route with disastrous consequences.

Thanks Bordonbert; though I will admit the help is too late unfortunately.

I like to tinker on stuff (I'm studying to be Electrical Engineer). I feel like looking into the amp and seeing what went wrong, I don't know, it seems appropriate that I at least try to understand the problem and see if I can fix it. That being said, I am aware of the lethal voltage the capacitors hold at times; so going forward I wouldn't touch anything unless it was very clear where the issue was. I've found in programming, that oftentimes you fix something at the expense of the rest of the program. I'm sure it's similar here.

If worst comes to worse, I'll have to find an amp tech but the nearest I know of is (Or at least advertising repairs) is about 100 miles away. So I would somewhat like to attempt to fix it. But I'll call my shots early if it's non-obvious.

Thanks, Bordonbert

Don't get me wrong Lateralus, I wouldn't want to stop anyone from opening up their gear and exploring.  I'm firmly in the camp of people learning the truth of how their gear works and being able to spot the myths by actually becoming engineering competent.  Knowledge is the best antidote to believing hype and legend.  It saves you from "mojo mindedness" where everything is magic so any old tosh can be stated as truth and be unquestionably believable.

The point is that, as you are aware, it is dangerous in there.  Lethally dangerous!  People need a certain level of skill and experience before they are safe to be left in charge of an open amp chassis.  If you are sure you are at that level, (which you have already answered), I'm happy to give you any advice I can on what you can do to try to fix things.

Unfortunately you will need test gear to get to grips with most of the higher level of repair.  A half decent test meter is a start and will help deal with the most common types of problem with amps.  An oscilloscope is not far behind to deal with chasing signals through and finding sources of noise.  I would guess you have a meter to hand but not a 'scope.  Ok, onward and upwards, if you are confident you will be safe and prepared to take that in your own hands let's go.

The high voltage PSU cap in the GM36 has across it a bleed resistor, actually a pair of them, so it should drain itself pretty quickly anyway.  Most decent amps have this nowadays.  I would still pop a meter across the line immediately after the rectifier diodes to check every time I went inside there after the amp being on.  You will know how to check out the fuse of course, just make sure to remove it from the clip or at least lift it at one end and use the meter to test for continuity, don't rely on your eyes.  My guess is that you will find the fuse blown and the answer is those Russian "equivalent" 6P41Ps.  They are not an equivalent at all, they cannot take the same anode voltages as the design EL84s.  I suspect they have broken down and caused the fuse to blow.  We have to hope that there is no other damage done as a result of this.  The only way is to fix the fuse, put in proper valves and try it.

When I said "resist the urge to fiddle" I actually meant in this area of valve swapping not in general.  It is never, never a good solution to alter the characteristics of an amp circuit by swapping in a different valve type unless there is a match of many parameters, not just an attractive value for one of them.  And people who advise you "I tried it and it sounds amazing" are themselves sitting on a ticking time bomb playing Russian roulette with their gear.  The substitutes for 12AX7s I mentioned are like that.  It is unlikely that you will damage your amp with them, but you could!  Every aspect of the stage will change and not for the better.  There is a reason why your warranties are often invalid if it comes out that you have done so.  12AX7/5751 yes, anything else no!

You cannot change the tone of any amp markedly by changing valves.  It is a myth and it doesn't stand up to proper scrutiny.  In  any comparison of component swaps you need to be able to compare the same amp for both examples.  The change has to be made quickly, in seconds, or the ear and brain self calibrate and you forget what you have heard before the change.  You then hear what you want to hear in the second.  And that leads us to another absolutely essential aspect, you cannot know which you are listening to.  This is the foundation of "Double Blind Listening Testing" which is the only way to genuinely see whether you or anyone can hear a difference.

Let's take tone capacitors in guitars.  We all know that Orange Drops or Bumble Bees or PIOs make your production line model sound like a Custom Shop don't we?  Well, as the price of those exotic caps rose and rose and rose from the everyday level which I remember them at in the '70s as they were just day to day components, to what they could screw out of you in the '00s because they were "old and golden", there came a time that Gibson started to use a cheap modern ceramic cap in their tone slots.  No one blinked an eye about it at first.  Then some "guru" somewhere blew the lid off and told everyone how shit their guitars now sounded and the balloon went up.  Gibson were dragged through the streets for saving a few cents by using a cheap totally unsuitable cap.  Only the truth is somewhat different.  That ceramic cap is an extremely good component.  If you bother to look at the specs you will find that it differs from the other "audiophile" caps as it has a tendency to rise in inductance at higher frequencies leading to a slight high frequency resonance.  That would make it harsh sounding and explain the difference.  Except this doesn't happen until you are in the region of a few MEGAHERTZ.  Even bats shrug that one off and I certainly don't know of anyone with radio receiver level ears.  Below that there is no distinguishable difference in the components' electrical characteristics and no one even suggests there is, they just "know" the ultra expensive tone caps sound better.

I have actually demonstrated this to people convinced they could identify their favourite cap without any problem.  So, take two caps of different types but of matched values to within 1% on a small toggle switch in the guitar cavity and out of sight of the guitarist.  Have a dummy switch wired in next to the real one.  An independent person operates the switches and acts as manager of the test tossing a coin and taking down the results in a table.  He tosses the coin and marks down what was the result.  If it is heads he switches the real switch over and clicks the other dummy switch over too.  If it is tails he switches either the dummy twice or he can switch the real switch twice.  The dummy switch acts to remove any chance that the guitarist can perceive whether the real switch has been changed or not, in all cases there will be two switch actions.  The guitarist plays for as long as he needs then guesses whether it is the "tone" cap or the other crap cap he is hearing.  His result is marked down against the result of that coin toss.  The guitarist must be told nothing about how his guesses are working out!  The person managing the test should try to not follow what is the state of the guitar and whether the guitarist guesses correctly or not.  It takes a large number of these tests to get results which can be statistically significant and prove something.  If you do it only 4 times you could get 5 different outcomes in terms of correct guesses.  Consider a 2correct:3wrong result.  Is that enough to have a high degree of faith that the guesser cannot hear any difference?  No.  But if it becomes 20:30 then we are onto something.  Yes it needs a bit of statistics applied to prove any result but it isn't hard to do and see whether there is any likelihood that a person can hear anything at all.  I've done this with very well meaning golden eared gurus a couple of times and never had anyone show any signs of hearing a difference let alone an improvement with their own preferred cap.

Do you know what?  It's always the test, or the statistics, or the other gear, or the room, or the fact they have a cold which masks it.

Okay, so I finally received the fuses in the mail. I replaced both 400 and the 800 ma fuse to be on the safe side. Reassembled it (In it I have 3 Tung Sol 12AX7's along with the original 4 chinese EL84's. This was the last working setup I had before I swapped the chinese tubes for the soviets. Just so you know, I swapped in the Tung Sol's about a month before the Soviets. In that time they saw the regular use and I didn't notice any issues), turned it on, and voila! it works!

But then after playing it for some time (5 minutes), I noticed something I can only aurally describe as a combination between and echo layered chorusy hissing sound when I played. It wasn't a good chorus sound, it was something like a second simultaneous note being played underneath the original, but it sounded like shit. Then it also seemed to take to squealing with feedback issues, which I'm familiar with that being sometimes normal with speakers and microphones but this seemed like it came on faster and took "less playing" before the onset of the feedback.

I've read about microphonic tubes, it seems to be preamp issue to my understanding, but I'm not holding to any data I find (That got me to buy this soviet shit). I'd imagine it's a tube issue though, because it sounds somewhat dynamic and almost random, almost like it has a liveliness; this being a quality I find in tube amps specifically.

I could be wrong, and Bordonbert you seem to know what you're talking about, so frankly do you have any idea what the causation is?

Note, I didn't bother biasing the tubes because of that TSC (in the manual it says it bias' automatically). Could that be an issue?

Also going forward, what tubes should I be looking for and what tubes should I be watching out for? Because I as of my current knowledge I still don't understand what makes one EL84 appropriate over another one?

Thanks

Lateralus

Glad it's at least up and running Lateralus.  Let's see what we can do.

Firstly, you won't need to bias the new valves in any way as long as the TSC is working correctly.  That is, assuming it has not been damaged but it doesn't sound as though it has been.  I would check it out by putting your Plectrum into the slot on the back to press the test switch and counting the flashes for each pair of valves.  The outer and inner pairs of LEDs should be within about 4 flashes of each other.

Next, get into your manual and check out doing a factory reset.  This will probably not make any difference as the nature of your problem seems unconnected but it is a step which it might be wise to take just to rule it out.  It isn't impossible for corruption to aspects like Gain or Effects settings to creep into the channels and patches and these can be universal.  We have just recently had a case where this solved someone's problem and it was only as an afterthought that I mentioned it.  A reset will put these completely back to stock so bear in mind you would lose any voice patches you have created and stored.

Next, is it possible to take the output from the Effects Loop Send into a different amplifier, preferably into the second amp's Effects Loop Return then do the reverse, take the signal from the second amp's Effects Loop Send into the GM36's Effects Loop Return?  That would show for sure whether this effect is being produced in the preamp or the power amp sections, (or in both but that sounds pretty unlikely).  I would expect it to be in the preamp section as you have now replaced the valves in the power amp but you never know.

Are you testing this through all channels and with all effects switched off?  If not do that and see if the noise is there for each channel.  This may give us an idea of which valve, assuming it was a valve, could be at fault.

Do you have a spare known good 12AX7/ECC83 available to substitute for each preamp valve in turn?

I'll be honest, I think it was feedback from the guitar amp and the guitar. My work space is really small (student here), which works fine for small projects (mostly dealing with things that don't involve sound) but the Tubemeister 36 combo is a decently large amp by size, so that and the confined space I think was causing serious feedback. Because I've been playing it at various levels since then and it seems perfectly fine.

Also since it been about a month and a half since I had last heard it, I had forgotten how "hissy" it is; if that's the right word? I really love the tone of the Hughes and Kettner, as I feel they've captured the heart of what I feel like made the amp's of the 60's and 70's legendary, without being consumed by their legacy. They appeal to the fan in me, yet they do enough of their own thing that I don't feel like I'm copying the next guy.

But that fizzy hiss, god! It sounds like airy filtered static. I'm new to having my gear. I grew up in a musical household, with multiple amplifiers, guitars and effects; but I was the youngest and everyone else was in these various stages, where they found their perfect tone and they couldn't really see why I felt it was lacking. So experimentalism was encouraged, but only with their gear for their style of music lol.

A few things I've noticed: While I like the distortion and the characteristics of the dynamics of the amp; I find it lacks warmth? Maybe. It sounds a little cold and sterile, chimy, icy, sharp metal. Thin? Idk exactly what it is, but that was part of my main motivation for the changing the tubes. I really love the good parts of the amp, and I feel like it stands out well on it's own which I love even more, but I'd like a little more warmth if that's possible. You mention tubes don't really matter much. Is there another way to have it sound more warm?

Another thing, is that hissing. I don't think it's feedback, it seems like it's more of a characteristic of the distortion. It's almost like there's a core note which sounds great but then the way subharmonics get caught by the gain in a way that pulls them out in like a wispy way. Fuzz I would say is denser, and this is more airy.

I apologize if this doesn't make sense, I'm just trying to discover my sound by following my ear. I love the amp, and I want to see what I can get out of it.

Thanks

Good to hear you've got it under control a little more now.  There are a couple of points which you mention on which we can offer a bit of advice.

The hiss is unusual if it creeps down into the Clean/Crunch gain level.  With the high gain channels it must be expected a little.  There isn't a high gain amp made which is completely silent, it's the nature of high gain!  I've never known my own TM36 or GM36 to suffer from it, at least on the Clean and Crunch channels.  I would be surprised if it were a feature of the GM40D as well.  It sounds like either you are playing with a shed load of Gain and hitting the amp input hard with maybe pedals which boost the level, or you may have a noisy preamp valve as well as the power amp valves you have changed out.  Hissing and popping are common signs of a preamp valve problem.

Try swapping round the preamp valves V1 and V2 temporarily.  That's the can covered one and the one next to it.  Make sure you mark them in some way to be able to put them back in their original places.  Numbering them with a felt tip pen near the point on top is not going to hurt them in any way despite what the internet may tell you.  They aren't halogen coated bulbs just plain glass envelopes and it has been done by every true valve expert since the invention of the valve!  What you are looking for is a change in either the volume or character of the noise.  If there is a significant change then it would point to one or more of the valves being on the noisy side.  If the level increases then it suggests the noisy valve is now in the V1 position.  If there is absolutely no change then put the valves back and swap V3 with V1 to apply the same test.

As to the lack of warmth you have experienced, that has been a complaint since my own first TM36 days.  I still maintain that the Germans at H&K Hauptquartier have as their design benchmark a metal sound matching their favourite rock music genre.  They simply cannot comprehend criticism of their amps based on people's desire to soften them down.  You have to learn how to use the amps to get the best of them for anything other than high gain rock and even then there is a limit to how far you can take them.  People maintain that the GM40D is now a much more refined sounding amp than the TM36 and GM36 but, as I have said before, I can't hear it, at least on the many YouTube reviews I have looked out.  So how can we moderate it?

First, the secret to good base tone is not valves at all, it is speakers.  (I had better point out that, that's base used correctly as in "a foundation" not bass "the bottom of the frequency range".  Guitarists note the spelling!)  These amps are incredibly finnicky about what you partner them with.  As mine was a head I could swap about easily.  I found Celestion V30s impossible to live with.  Using them I could not get rid of the ear-slicing top end and the prominent raucous upper mid, as well as a complete lack of anything at the bottom end as witnessed by a useless Bass control which did nothing at all.  I changed to my 1960s Marshall 4x12 now loaded with G12M Greenbacks and things settled down a lot.  It still wasn't balanced through the mids in a way that I wanted but it did cut down on the hardness at the top and added in a bit of bottom end.  Those who prescribe to the concept of "cutting through the mix" seem happy with that, personally I think it is just another industry marketing soundbite which guitarists latched onto and now use to let others know they are "proper" guitarists.  I wanted something more classic sounding in the true "classic" sense and I had to make greater changes.  That eventually led me to a Marshall which I now use as a gigging amp and I keep the GM36 for home use only where I can use its strongpoints without worrying about its weaknesses.  As you have a combo I would have thought that the H&K speaker, which I believe is a V30 specially voiced for H&K by Celestion, would have been a good match but trying the amp with different speakers would let you see if there is anything to be gained by swapping out.

You may be experienced enough to know about the following but, if not I suggest you try this...

Using these amps is much more complex than a more standard rig like a Marshall/Fender.  They have a solid state input buffer built into them before the valve sections.  This is set up to be a totally clean buffer, a creamy mild assymetric overdrive and a full out distortion unit depending on the level of signal you feed it with.  It is extremely well designed and prevents any of the effects which people incorrectly claim solid state circuitry must create.  All of this is before any control in the amp other than the Boost switch so, once that choice has been made, it responds to nothing other than your guitar/pedal volume control.  As I said, it is a mistake to just slam this with the highest signal you can, in the hope that you are driving the valves into creamy overdrive.  Set up with only your guitar into the amp, no pedals at all, switch the Boost off and throttle the guitar back to about one third on its volume control, that's about 3-4.  Select the Clean channel at an appropriate power setting, apply a mild amount of Gain so you get into some sustain and feel but no real hard grit and set up the Volume and Master so you have a sensible playing sound.  Now increase the volume on only the guitar and see how the character of the sound changes.  If you need to drop the volume at the amp, only use the Master Control, don't touch the Gain.  When you max out lower the volume, kick in the Boost and repeat.  You should be able to hear the level of overdrive changing as the volume increases.  Controlling that change can only be done at the guitar/pedal end, no control other than the Boost on the amp affects it in any way.  What you hear will not be your final desired sound, that isn't what you are looking for yet.  It is not using the valve overdrive much at all but you should see that there is a separate distortion mechanism which is subtle and useful and which won't give you its best if you just whack it up to the max as most people do.  Once it is overdone at the input it can never be tamed after that point.  You don't really need your overdrive on the pedal board once you can use this function on the amp.  And I should point out, this is entirely deliberate and made by the good design of the H&K tech guys!

Now throttle the guitar back to one third and select the higher gain Lead channel.  Play with the Gain until you get a sound a little below the distortion content you would like and balance the volume on the amp.  You should find the character of this sound should be a little different to the first test as it now has valve distortion without any contribution from the input "Tubescreamer".  It may well sound a little thin but stick with keeping it just on that side.  Now gradually increase the guitar volume and listen for the input overdrive coming in.  Stop when it feels as though it is just thickening the sound enough for your taste.  Hopefully this will give you an idea of how flexible these amps are and how easily they can be "over-overdriven" if you aren't careful.

You will find that getting the right blend of the two distortion mechanisms is one of the keys to finding your own preferred tone and removing as much of that roughness as you possibly can.