Mesa LSS acting up

[Jared Purdy]

I figured that if any site might ave some insite, it woudl be this one, so here it goes: Okay, last week, my (one month old) amp was making some kind of crackling sound (I forget which channel), and then the rectifier tube went (I called the place where I bought it, and they suggested it might be the rectifier tube, try that first, and then look at the power tubes). I went to the local shop, while they don't carry Boogie tubes, they had a Sovtek, so I brought that home, fired up the amp, and we're in business.

The next day I went to another store that had Boogie rectifier tubes for the LSS, bought one (warranty issue using non-Boogie tubes in Boogie amps, but hey, the tubes are warrantied for 6 months, so that's okay with me), went home and plugged it in. All's good. So far. Played off and on for the next couple of days, then same thing, crackling. I turned the amp off, consulted the manual. Several things were mentioned: faulty power tube, possible rectifier tube, it also said to watch out for miniature lightening storms in the rectifier and other tubes. So I flipped the amp around, turned on the power supply, and shazzam! Lightening in a bottle! In the rectifier tube. That's the 2nd Boogie tube, and a new one to boot. Before I had a chance to shut it off the fuse blew. sh!t!

So, off to The Source, picked up the right fuse, got home installed new, and everything is okay. Today, as I'm playing away, experimenting with the different wattage settings, I had it on the 30 watt setting, and start to hear crackling again. Blew another fuse. Put in one more, blew it too.

So, I called Boogie. As useless at tits on a bull. So I called the repair palce at Steve's Music (where I bought it). Matt had some interesting ideas. As he can't see it until Monday, he suggested this: go buy more fuses, before I install one, remove the power and rectifier tubes, then install the fuse and turn on the amp, in standby, wait, and then turn standby to on. If the fuse doesn't blow, that narrows things down a bit. He then said, to turn the power off and put the spare set of new Boogie power tubes that I have in it. And install the Boogie rectifier. So I did all of that, and within about 3 seconds, there was a lightening storm in the rectifier again. I turned it off immediately, and put the Sovtek recitifier tube in. Still working. What gives? Any ideas? Anyone else have similar issues? Thanks for your time.

[Steve Conner]

Jared, it sounds like Boogie got a bad batch of rectifier tubes. I'd use the Sovtek, but save one of the Boogie parts and put it back in if you need to send the amp for warranty service. If you don't get any crackling, blown fuses, burning smells or other weird behaviour with the Sovtek, I'd consider the problem solved.

Another possibility is that some other part of the amp is drawing too much current, which a Sovtek rectifier's military-grade mojo can handle, but a Boogie-branded rectifier can't. But you probably covered that by trying different power tubes, since they're the part most likely to draw excessive current.

[Jared Purdy]

Hi Steve,
Thanks, I was not aware that the Sovtek was military grade. Funny because when you look at the physical construction of the Mesa tube compared to the Sovtek, the Mesa tube looks and feels much more substantial. When you shake the Sovtek tube you can hear a bit of rattling, and you can also hear a bit of that when the volume is up a bit on the amp. I put the Mesa tube in quickly last nite as a experiment. Sure enough, just as I turned the power on, (Standby off), it crackled and blew the fuse before I had a chance to turn it off. I put the Sovtek back in, and as of last night, it's fine. I hate when these things happen to products that cost as much as a Mesa LSS costs. I tend to lose faith in them. That's interesting what you say about a part of the amp drawign too much current. I believe that is something that the tech at the store where I bought the amp was musing about. I'm going to take it in on Monday, as I no longer trust it. When I hear back, which I was told would just be a couple of days, I'll let you know what they tell me.

[Pedro Vecino]

LSS is Lonestar Special, yes?
Problems with rectifiers and power tubes are more common than desirable.
In this amp EL84´s operates very hard. In the last unity I d´ont remember exactly the dissipation at idle but it was near to catastrophic ż15/16 watts?.
The rectifier has in line 110uF. One solution is to use good NOS american 5Y3.
About power tubes, I use in these amps strong E84L Siemens (7320) with manual bias adjustment (very complex automatize in all modes). This EL84 is the most powerful model that I know and with a extra power. However, as they are expensive is preferable to set the proper bias.
Regards

[Steve Conner]

Pedro, are you suggesting that the LSS is a poor design that overruns the rectifier tube?

The 5Y3 datasheet specifies a maximum capacitance of 20uF, you said the amp has 110, is that all on the first node?

If that is the case, no wonder the rectifier blows up now and again. (maybe Mesa want to sell more Mesa tubes? ) I'd stick a 5AR4 or even a Weber Copper Cap in it.

[MWJB]

As long as that 110uf filter is on the hot side of the standby, then there won't be a problem in that respect. If on the other hand, excess idle current is the problem, a higher voltage rectifier may exacerbate the issue?

[Pedro Vecino]

Not a bad design, but very forced in some aspects. LSS is an "adaptation" of the Classic (4x6L6) to expand market (is what I think) and is not the first time that Mesa makes a hasty work.
6P14P (EL84 Russian) are strong tubes but are subject to very hard work in this amp. Russian rectifiers (5AR4, 5Y3...) are not as strong and can not compete with older designs. I´ve seen Mullard GZ34's with 40 years working like the first day. Impossible with current rectifiers.
110uF (2x220uF in series) go directly after rectifier, and with reference to the Classic this filtering is necessary to maintain tension in the lows. Can be reduced but would remain quite soft.
I think the specifications of maximum capacity in many rectifiers are very conservative. Many of them support a lot more, but it must be good.
5AR4 (GZ34) is not suitable because it would increase the high voltage and I d´ont know what would happen with the Copper Cap and the activation circuit (Tube rectifier is always active and is the diode-rectified voltage which is superimposed. Same as 3 channel rectifiers).
Standby is after the 110uF

[Jared Purdy]

Thanks for all the feedback. Unfortunately, most of it means little to me, but I suspect it will mean something to the amp tech at Steve's Music, who will be looking at my amp either Monday or Tuesday. As a recap, (posted in the other thread) the new Mesa 5Y3 that I picked up yesterday is working. Maybe it was some bad tubes, but what took them a month to start acting up?

[MWJB]

Current usually is what kills tubes. If the amp is working OK it should take a a year or two of heavy gigging. If it's biased cold it might take 10yrs of heavy gigging (assuming it sounds good enough to gig). If it's biased very hot, it can take anywhere from minutes to "up to a year or two of hard gigging". The harder you push a tube, the shorter its lifespan...tyre analagy again - good pressures, sensible driving and they last thousands of miles. Insist on leaving black rubber marks all over the road & doing donuts at every opportunity & all bets are off.

[Jared Purdy]

Hi, thanks, and good analogy. I've read that Mesa biases their amps cold. Is there a way to change that, like to something moderate (as there is no bias pot)? When I was swapping the dud Mesa 5Y3 yesterday, one of the store clerks said that Mesa tubes are generally considered crap, the worst part of the amp. He went on to say that Mesa's amps are made very well, and they have one of the best PCB designs in the industry, incorporating some PTP (like attaching pots and tube sockets). He wasn't trying to smooth me over because I didn't buy the amp at that store, and he doesn't use Mesa amps himself.

I'm not sure what to think. If I pay $2000, I expect it to work well, and last a long time, and be devoid of any of the annoying little issues that plagued my previous purchases. I know that alot of tubes rattle, though that was never a problem with the PRRI, with either the stock GTs or the Tung Sols that I later put in. The C30 has inherant tube rattle problems because of the design of the chassis, the way the tubes are mounted to the chassis, and the tubes proximity to the speaker. It wasn't the tubes, it was the amp! The Mesa 5Y3 doesn't rattle at all. The one that was in the amp, before it blew, didn't rattle at all, at any volume, the 2nd one I put in, didn't rattle either. The Sovtek rattles before you even put it in! If you shake it, you can hear the plates moving - but it doesn't blow up!! The new Mesa 5Y3 that is in there now doesn't rattle either. I'll take a picture of both tubes later, and see if I can't capture the plates. Maybe one of you guys will know a little more about them. I don't gig, my amp sits on an Afghan rug in my dinning room, always toasty, always clean and dry, never being moved (I don't take when I go away for a couple of days as it's too damn heavy, and takes up too mych room in the trunk, compared to the PRRI (which I sold, but is soon to be replaced with Headstrong Lil'King or a Vintage Sounds VS112PR). In other words, my amps don't ghet any abuse of any kind. When I'm home alone, I usually play in the 15 watt setting, with the volume set to about 10:30 on both channels, which loud, but not insanely loud. When the wife and kid are home, I turn it down, and drop down to 5 watts.

[MWJB]

"I'm not sure what to think. If I pay $2000, I expect it to work well, and last a long time, and be devoid of any of the annoying little issues that plagued my previous purchases." The thing to be aware of is that the tubes theselves have no concept of currency...they only know the environment that they work under. Mesa don't make tubes...no amp manufacturer does, whether an amp costs $200 or $20,000 it is likely to have the same current production tubes in it...the difference in price comes down to how labour intensive the build, cab & transformer quality etc. Those same tubes used by Mesa may sound great & be perfectly reliable in other amps, even other Mesa's...maybe even in your Mesa with a minor tweak (no guarantees though). If the idle current is too high, your tubes are getting hot just by having the amp on...without you playing through it. When you switch to 5W mode, one tube is working its damn ass off making that 5W, because that's the most that 1xEL84 can make on its own. Basically, I'm saying the different W modes written on your amp's faceplate don't really match up with how hard the tubes have to work. I can see that this doesn't appear logical, but it is the case..."W dc dissipation" kills tubes (like high idle current) & basically means the heat they can take, "W AC RMS" is a measure of the clean signal the amp sends to the speaker - very different things & somewhat counter intuatuive.

[Jared Purdy]

I realize thhat what I'm about to say, will not come across as technical, or scientific, but the back of the amp does not "feel" hot to me, any more so than what the PRRI felt, or the C30. I've put my hand right in there, and, up close to the tubes. I'm not sure if you are aware of this, but the LSS is fan cooled, and I leave the fan on all the time when the amp is turned on. Please explain, for me what "idle current" is? What is responsible for it, can it be changed, if so, how? Thanks.

[MWJB]

Idle current is like the idling revs on your car, it is also called bias current. If it is set too high the tubes will always run hot, perhaps hotter that they should (e.g. if your car idles at 5K rpm it will get hotter & use more fuel). If the bias/idle current is set too low the amp may sound thin, cold & scratchy...in extreme cases long notes won't reproduce properly and the amp will choke up. You won't really be able to tell this by feeling for heat with your hands. Idle/bias current is changed either by manipulating the bias voltage divider in the circuit (note the references to amps with a "bias pot" - Mesa do not fit bias pots, you will have to change resistor values in the amp), or by selecting tubes that idle at an appropriate current (even tubes of the same brand have differing characteristics - Mesa pick a middle of the road value & hope that their brand of tubes work within a given range, but due to typical manufacturing tolerances they might not). I do not recommend altering the circuit if the amp is under warranty and you are thinking of selling it/trading it in. Going to a tech with a good selection of tubes & have him cherry pick a set that your amp likes is the best course of action.

[Jared Purdy]

Thanks, That clarifies that issue quite nicely! Yes, the tubestore.com has got as couple of tube packages for the LSS. I have no idea how they run compared to the Mesa tubes. The current preamp tubes that Mesa uses, as I was told by their CS department, are JJs. He didn't know what the power tubes were. One of the tube sets that thetubestore.com recommends are JJs (the "economy", or "budget" tube) with a Sovtek 5Y3. The other tube set is the "Preferred Series" made up of 7189 tubes, NOS Jan Phillips 12AX7WA preamp tubes, and the Sovtek 5Y3. Mullard also makes an EL84, though the tubestore doesn't include in the recommened sets for the LSS. I looked at every EL84 thetubestore carries, not one of them resembles what's in the Mesa.