TubeMeister Deluxe 40 replacing tubes

Hi Guys,

Do I void my warranty if I change a bad tube or two?
My Deluxe 40 seems to have a large appetite for tubes.

Thanks

Hi TBone, welcome to the forum.  No you won't void your warranty as long as you follow the specified method for opening the amp up.  The amp has anti-tamper checks fitted on its lower screws internally.  These will be broken if you remove the screws too far showing you have been inside it so the H&K trick is to do the following.

1. Remove the top two screws from both handles
   
2. Remove only the rear screw from the centre strip of both handles leaving the front one untouched, it only holds the chrome strip to the end cheek
   
3. LOOSEN the two lower screws ONLY A FEW TURNS, just enough to let the side panels flop outwards to remove the cover
   
4. When removing the cover look out for the LED PCB which sits in clips beneath its front lip and be careful with the two wires feeding that PCB on the right as you look at the front
   
5. When refitting make sure the PCB is fitted correctly first and its wires are neatly dressed.
   

You shouldn't really have too much of a problem if you are at all handy with simple tools and fittings.  It's really over the top to expect us to visit a guitar tech every time we want to pull or replace a valve or two.

As to valve wear, preamp valves in a well designed stage should last a very long time, there is no hard life for them even when driven into distortion with one exception.  V2 in our Grandmeisters (that's T2 to H&K in their schematics) contains a DC coupled cathode follower stage which can be very hard on the valve doing that job at switch on driving it way outside spec maximum voltages during warm up.  It is reported with good factual evidence that Chinese ECC83s (the English code for the 12AX7) are more hardy when set to do that job.  If you were to use a Chinese version for life expectancy then it also means using one of them in the final gain stage slot of course as they are dual triodes.  I'm personally not a believer in the night and day differences in sound reported between valve makes.  It's musical hype with everyone "knowing" they sound different because everyone tells them they sound different and, of course, the Emperor has new clothes.  The differences you hear with a valve change are not down to the manufacturer of the valve at all.  I'm an old electronics engineer and I know how component specification works and the characteristics and plots for these valves fairly well by now.  The "valve manufacturer character" thing is absolutely NOT held up by any factual engineering evidence and there is solid evidence to show it really is a non-issue.  If you are a believer in that side of things then you just have to accept that, using your own favourite flavour of 12AX7, your choice for V2 may not be as long lasting as the Chinese makes could be.


EDIT: Just a heads up here. I have just realised you have the new TM40D! That has the 3x 12AX7 configuration as the big boys in the other models do, 2x preamp and 1x phase splitter. I talked about the DC Coupled Cathode Follower earlier but I've not definitely seen proof that that is the setup for the TM40D. I would really strongly guess so as there is a distinct family feel to all of these amps and the others with 3x 12AX7 have that configuration.

Thanks for your prompt response bordonbert.

To be fair this is my second Deluxe 40, the first one was purchased in November 2018.
I had to have the tubes changed out twice on this unit (see repair slip 1 & 2 ) the last tube change occurred early Nov. 2019 and before the end of that month the unit failed again.

At this point, my dealer replaced this unit with a brand new Deluxe 40.
By the end of January this year the new unit had failed and was in for repairs (see slip 3).

Hear we are at the beginning of April and I’m getting flabby low out put sound, especially noticeable when in the Crunch or Drive channels.

I have noticed a pattern now, once after a jam and most recently at home; both times I had left the amp on stand-by for an extended time, perhaps 40 mins. and the next time I turned on the amp it was flabby and had low output. Unlike the previous issues, the amp did not die completely.

Here at home a few days ago I took a break from playing and was distracted for about an hour while the amp was on stand-by, again low output and flabby.

Over the following days, the output seemed stronger but quite distorted.
Last night both Crunch and Drive channels seemed fine, well better anyway.

I really love this amp and do not want to give up on it but I’m an expensive ferry ride away each time I have to travel to my dealer and repair centre.

Any insight into my issues would be appreciated.

Be well.

That's very interesting. There is a background here.

Using the normal Standby with any valve amp is a BAD THING! If you want a bit of technical info which tells you why here it is: Standby Is A Bad thing. You won't need all of the technical info unless you are interested in circuit design but there is historical info there which should give you the picture if you sift through it. This guy really knows his valves and apart from that the theory he describes is well known and flawless. Usually what happens with Standby setups in guitar amps is that the HT is removed from at least the output valves leaving them heated and ready to go but with no current running through them. This causes a microlayer of resistive material to gradually grow under the oxide coating of the valve cathode. It is high resistance and gradually reduces the valve's ability to pass current to the point where it becomes useless. The technical term is "Cathode Poisoning" and it is documented in the bibles of valve technology from the 1950s when people REALLY knew their valves, (unlike nowadays where the internet has given rise to a new crop of "gurus" who don't really know the truth they just know what everyone else says they believe and it can't be questioned in any technical way or it offends peoples' "opinion". Yes, people cannot distinguish the difference between fact proven by evidence and opinion nowadays.). Severe cases are irreversible but there is some practical amateur evidence that some valves can recover given time in use but possibly not back to where they were fully. (I'll try to dig this out and post it here later for anyone techy enough to be interested.) It usually takes a long time for this poisoning phenomenon to occur, I've never heard of it happening in an hour or two, but it seems to me this could perhaps be part of your problem.

In the GM36, H&K apply a different approach to their Standby to others thanks to the TSC setup. Their amps have circuitry in the output valves' cathodes to monitor and control the bias current automatically. That's the TSC setup at work. They use these components to drop the bias (or standing) current and to prevent any increase due to signal while the amp is on standby. It has been reported before that some amps do play a very low level signal even when in standby. People actually bitched about that as if it were a fault even though it was necessary to put your ear to the speakers to hear it. I had always thought that H&K had built protection into that for the output valves from losing all current completely by leaving the cathode control setup slightly conducting. As the control for this area is locked up inside the digital section it is difficult to know if this is the case without a bit of internal investigation and I've never had the time and opportunity together. I had assumed the GM40D was exactly the same as the GM36 in this area but in your own case at least it seems that it may not work like that and putting the valves on Standby is not doing them any favours.

I can assure you that the best way to deal with this is to ignore any Standby switches on any guitar amps and simply use the Master Volume to turn it fully down! After all, how hard is it to turn it back up to the level you want when you come back to play again? Your valves will not "wear out" by sitting idling, that's another stupid musical "mojo myth". I have never understood why getting your head around doing that is a problem for guitarists. It's almost like "there is a control on there so I WILL put it to good use". Vox and Gibson made their first amps without any Standby system in them at all, and Vox actually screwed up their amps when, at a later date, they decided to fit them because "everyone else does it and guitarists expect it now".

If Standby kills your valves then...

Don't use the Standby!

Just done a PROPER look over your receipts.  I really should have taken more notice of your info and done that before!  Durrrhhhh!

Yes, there it is in black and grey, output TSC control FETs replaced - twice.  That is something we see very occasionally but it's very unusual to have the same problem twice.  I wonder if it was down to the same original event and the second replacement was just due to a stressed FET giving up the ghost later.  With damaged FETs the TSC control cannot have been working as it should so bias current control would not have been reliable.  It's hard to speculate what would have been the cause and effect here.  If you now have working FETs and a decent set of valves then we should hope you won't have this problem again.  If it does reoccur it points to there being some other problem causing it.  It is possible there could be damage to the TSC board but don't lose sleep over that, wait until it happens again before you start worrying.

As to the valve replacements, there is absolutely no advantage in sourcing your valves from H&K.  The mark up at each stage from the factory to you is ridiculous.  Any valve choice from any source will be as good as those originals.  They aren't the "tone throttlers" that some people will insist they are.  I have spoken to a few people who actually prefer the tone they get from those "cheap" originals.  They just don't come out and broadcast it because of the flak that they get from the "tone junkies" who insist that anything that is over 50 years old and shagged out must perform better electrically and sound great to their pixie dust bat ears.  The truth is on a valve tester and in a parameter measurement setup!

Most people here just use a set of standard reasonably cheap very reliable JJs.  You can get them anywhere for a reasonable price.  I've used them in all my amps as I have tried them against other available types like EH, Harma, TAD, Sovtek, Shuguang and others and I have found that, AS LONG AS THEY ARE IN SPEC, there is no genuine audible difference between them.  What is it that people can't understand about this point?  You decide it's time to swap your valves as your amp is starting to sound tired.  You replace your clapped out old JJs with a new set of guaranteed good NOS Mullards you got on ebay   .  They sound better!  Conclusion, old Mullards bought from an undisclosed ebay source blow away JJs.  Except that you have forgotten that the JJs you are replacing were being replaced for a reason, weren't they?  They were clapped out!!!  Of course, you may have your own preference on this but I always caution people to simply use their common sense and logic in valve swaps and don't get caught up in the "there MUST be a better sounding option if only I can find it" hype that surrounds it all.  We're almost getting to the point where "some makes sound better at the weekend while others are better for weekday gigs" stupidity.  All of the genuine electronic evidence shows that there is no consistent significant difference tonally between 12AX7s from different manufacturers in guitar amps.

Have a look at our old friend Voodoo Jeff's posts here concerning his Wathen valves:  Do your Wathen valves sound different? They start at post #122. VJ is a professional musician doing a lot of studio work as well as live stuff so his need is more critical than a jamming or gigging user like most of us. His Wathen valves currently cost over $85 for a single 12AX7 and $95 for a single EL84. Do they sound that much better?

Great information bordonbert, thank you.
The Standby will be used judiciously going forward.

bordonbert wrote:Just done a PROPER look over your receipts.  I really should have taken more notice of your info and done that before!  Durrrhhhh!

Yes, there it is in black and grey, output TSC control FETs replaced - twice.  That is something we see very occasionally but it's very unusual to have the same problem twice.  I wonder if it was down to the same original event and the second replacement was just due to a stressed FET giving up the ghost later.  With damaged FETs the TSC control cannot have been working as it should so bias current control would not have been reliable.  It's hard to speculate what would have been the cause and effect here.  If you now have working FETs and a decent set of valves then we should hope you won't have this problem again.  If it does reoccur it points to there being some other problem causing it.  It is possible there could be damage to the TSC board but don't lose sleep over that, wait until it happens again before you start worrying.

Well it looks like it's time for me to start worrying...it's happened again.
With all channels on my normal settings, the clean channel is barely audible, the crunch channel is horribly distorted, only the lead channel seems to function somewhat normally.
And even it sounds off.
I have to say I'm losing patience with these amps and with the Covid thing I can't even get it repaired (again).
Sure wish I could talk with someone from H&K.

Darn, that was not what I was hoping for!  I really think the situation now needs someone with the amp in front of them to have a look see T-Bone.  It certainly looks as though the problem lies beyond just the valves and MOSFETs themselves.  I would be curious to know what the TSC LEDs are reporting now, could you try that and post the results?  I don't like the link with your Standby at all here.  H&K use a different approach to standby to most amps as I said before.  It makes me suspect that there is something more fundamentally wrong going on here than just those blown MOSFETs.

You can actually talk to H&K usually with a pretty reasonable turnaround time through their Facebook page.  I have always found that emails and online forms are hit and miss with H&K as their support guys are always in and out of the office for shows and the like but their FB page can be monitored easily on the run so they tend to respond there.  You can get to it via a link on their website at the base of most pages.

There is a hearty mix of valve/solid state/digital circuitry in your amp which does need a different skill set and experience to deal with easily.  Is your amp tech a H&K recognised guy?  I don't know where you are in the world, (I would guess West of the Atlantic), but H&K usually have their own set of authorised service centres which are much better places to take them.  I'm not doing your guy down but remember, this is not a classic "rat's nest chewing gum and string" old style classic valve amp which is what most old school amp techs will swear by.  There are good reasons why they do that swearing by older point to point designs and it isn't because the new approach is inferior!  It's more to do with their ease of repair and sometimes to do with learning the necessary new skills to be able to easily cope with them.  Why do you think that PCBs are universally hated when they are a given for consistency and reliability in every critical area of electronics, whether space, avionics, military, medical, wherever life depends on it?  PCBs require a different skill set and understanding of their benefits and drawbacks to work successfully with them.  Too many techs hate the extra work that repairing them can require and don't honestly appreciate and acknowledge the benefits beyond "they are cheaper for the company to manufacture".  I am leaning in your own case to the need to maybe swap out the digital TSC board though some of the drive circuitry on it may be fixable with general components.  Most of it is surface mount and techs usually can't (or won't) touch that.

Just as gossip...  When I have down time I sometimes entertain myself by watching the occasional YT vid with self proclaimed "techs" repairing amps.  The totally incorrect information some of them come out with about even basic circuitry and how it does what it does is unbelievable.  And these guys are heralded as "mojo gurus" by those with no understanding at all.  As the old adage goes, "In the country of the blind the one eyed man is king" and it has never been more true than in musical electronics.  There is another principle to remember here too, "you can't con a man who doesn't want to be conned".  And boy do musicians often want to be taken!  They believe any old twaddle which completely contradicts tested and proven engineering results and pant to get accepted into the priesthood of the knowledgeable by bringing factual expertise down to a lot of "common knowledge" quotations and "opinions".  The general tech approach often really comes down to "building with Lego blocks" rather than based on electronic understanding and, for the classic simple designs, that usually works fine.  But that is the difference between the titles and job descriptions of "technician" and "engineer" which most people do not appreciate.  The tech must know the units, the engineer must know the principles.  The H&K philosophy is definitely a hi-tech modern approach and most "father to son" taught techs don't have the breadth of understanding to really know their workings when things get too tough.

But, as I said, before, I don't want to speak ill of your particular guy unfairly.  He may be very well versed and fully up to speed with what is going on in your amp and, if so, that is fine.  It would be good to ask H&K what their approach to the situation regarding repair in your area of the world is and if they have someone they recommend themselves to take care of servicing and repair on their behalf.  Is the amp still under warranty as this seems to me to be a straightforward case for another replacement with the problems you are having?

Thanks for your prompt response bordonbert.

You are correct, I live in the seaside town of Gibsons British Columbia a 40 min ferry ride away from Vancouver.

Here is what the LEDs are doing on start-up first try; 1W - all lights/ one flash then 2 middle lights
5W - all lights, no flash then 2 middle lights
20W - same as above
40W - all lights/ one flash then two left lights go out then all lights out.
I only tested it in the lead channel.

Hope this helps.

I take the amp back to my retailer, Long & McQuade (they are a nation wide chain here in Canada), from there it gets sent out to their repair facility.
I do not know what the repair tech's credentials are.

I think the TSC setup seems to be showing what it should - mostly!  I don't know how much of this you already know and understand but just in case...  The Power Soak circuitry works by adding in a resistor chain which is designed so the amp output sees a constant impedance no matter what level is chosen.  The resistor values are chosen so they drop a precise amount of the output power as heat leaving the reduced amount to feed to the speakers.  That's easy stuff to understand but there is another bit which people sometimes miss.  The first level of drop, from 40W to 20W, is done by pulling two of the output valves out of circuit.  That is why you see the two inner LEDs kick in for all of the selections other than full 40W.  They are indicating that those two valves, the inner pair, have been turned off by the control circuitry.

I think that the fact that sometimes at turn on you get an initial flash for some settings and sometimes you don't is not really relevant.  The TSC seems to be ending up where it should for each setting.  That "mostly" at the beginning was only there because of the 40W "left lights out then all lights out".  If this is just a second or two then it's no problem, if it is a longer time then it could be significant.

The TSC is a feedback system and all such circuits have a settling time.  It isn't surprising, taking into account the fact that this is a dynamic control of a static situation (the bias current), that that settling time should involve voltages taking a few seconds to reach their correct level when the system starts from cold.  Each valve is controlled individually by a totally separate path to allow each one to reach its own particular bias voltage for the correct current.  Those which need a higher voltage will take a little more time to ramp up from 0V.

The only thing I find odd is that the match seems to happen with the left and right pairs.  In the circuit the valves are paired to work as outer and inner pairs and the valve matching should reflect that.  One pair should be put in the two outer slots and one pair in the two inner slots.  The idea is to keep the currents of the left side, (either a pair or a single valve), always matching the currents of the right side no matter what the power soak selection is.  If we think of them as Left-Outer (LO) and Left-Inner (LI) and Right-Inner (RI) and Right-Outer (RO), for 20W the inner pair are switched off so we must make sure that we get LO = RO.  For 40W we must make sure that LO + LI = RO + RI.  i.e. the outer pair must be matched and the inner pair must be matched.  (And of course if we have a full matched quad then it makes no difference where you put them when you first get them as they are all the same.)

What you are seeing suggests to me that the left two valves LO and LI, and the right two valves RI and RO, may actually be better matches than the inner and outer pairs which are the important thing.  There are other factors in the circuitry which may be responsible for this little oddity but I would try the following test.  Swap valves Left-Outer and Right-Inner, switch on and see what the TSC does.  I would hope that now you would see the outer pair of LEDs work together and the inner pair work together meaning that the settling time has moved with the valves.

When you bought these valves were they two separate matched pairs or were they a full matched quad?  If they are two separate matched pairs but with the pairs not actually matching each other, (I hope that is clear), is there a chance you have them in the wrong slots?  I'll try to make all of this clear just in case.

Correct valve matching, (pairs are 'A' and 'B'):

Code:

 LO   LI      RI   RO
[(A)  (B)]  [(B)  (A)]

A = A (20W)
A + B = B + A (40W)


What you seem to have:

Code:

    ----- 20W ----
   /              \
[(A)  (A)]  [(B)  (B)]
   \    \    /    /
    ----- 40W ----

You can see that, if both pairs 'A' and 'B' aren't a match to each other, this would not give a match for left and right bias voltages, though the joy of the TSC is that it tries to compensate for this to a degree.


If you swap LO and RI:

Code:

    ----- 20W ----
   /              \
[(B)  (A)]  [(A)  (B)]
   \    \    /    /
    ----- 40W ----

The left and right sides now match for both 40W and 20W modes.  Of course the 20W mode is the basis for the 5W and 1W modes too.

This isn't a huge issue and may not make any difference to things at all, it's just an oddity which is easily ticked off with just knowing your valve situation and by swapping a single pair.  If it makes no difference or if it goes against what you know of your own valve matching, (I mean if you know you have the valves inserted in the correct sockets to give proper matching), then make sure to put things back as you had them after any investigation.

One last little bit of info, from H&K themselves, is that when you fit new valves the TSC takes some time to recalibrate itself to the new valves.  For a couple of uses you may find that the TSC readings are off as it gradually adjusts itself from the settings for the old valves to the correct settings for the new set.  People have reported this effect before and H&K confirmed it can happen.

Thanks for all your help and information.
Given the present circumstances, I guess my best option is to do a tube replacement.