Got new Tubes but having problems

[Lesser Known God]

OK, I ordered all new tubes the other day. I ordered 5 Chinese 12AX7's (CH-12AX7A), 3 matched set Electro-Harmonix 6L6's (EL-6L6GC), and 3 Electro-Harmonix Rectifier tubes (EH-5U4GB).

I proceeded to carefully replace all of the tubes and when I turned it on, it came on then turned off almost immediately. First thing I checked was the fuse and sure enough it blew. I just chalked that up to new tubes+old fuse=blown. Once I replaced the fuse it was fine.

Unfortunately, not only does it sound quite as good as the stock Mesa tubes, my BIGGEST problem is the Microphinics (I think that's what it is). I can't get natural feedback any more. If I try to carry a note until it feeds back naturally, It just turns into an uncontrollable squeal.

Any suggestions on how I can troubleshoot this problem?

[ May 21, 2003, 02:22 PM: Message edited by: Lesser Known God ]

[Firebird V]

Re: Got new Tubes but having problems

Maybe have it re-biased.... Just a guess.

[chrisolson]

Re: Got new Tubes but having problems

I'm not a tube guy, but I've heard that Mesa's are very finnicky about tubes, and that the best bet is to use MESA matched tubes. Just what I've heard - keep that in mind.

[Cleveland Metal]

Re: Got new Tubes but having problems

Sometimes you can get a bad chinese tube. They are excellent tubes, but they throw a bad one here an there. A possible problem.

Really though, the amp needs to be biased for different tubes other than the stock MESAs. And umm, Mesa amps are fixed bias... Best to get their color code, and believe you can give the color to some places and they will give a match. I'd still have te bias checked to make sure it was in spec.

Personally, I don't like the EH tubes at all. I use svetlanas, or I'd get whatever MESA sells for the app..

[Lesser Known God]

Re: Got new Tubes but having problems

First off, I am assuming this isn't a Bias problem as I went through tubestore.com to get the tubes and told them exactly what I had. They did a GREAT job matching up on my Single Rec, so I would assume they did the same for my Triple rec.

As for me going with Mesa branded tubes... Pete explained that. Why pay more for the same tube with a Mesa Logo on it?

Pete: To answer your questions: I got 3 6L6's because it's a 150watt amp. Thanks once again for all the great suggestions! I'll go through all those steps and contact you if I need further assistance! Pretty soon I'm gonna have to start paying you for your services! [img]images/icons/smile.gif[/img]

[Dreamland_Rebel]

Re: Got new Tubes but having problems

don't you mean 6 6L6's
each 6L6 is roughly equivilant to 25 watts that why the 100 watters have 4 50 watters have 2 and T-recs have 6.

[Cleveland Metal]

Re: Got new Tubes but having problems

As for me going with Mesa branded tubes... Pete explained that. Why pay more for the same tube with a Mesa Logo on it?

<font size="2" face="Verdana, Helvetica, sans-serif">Personally I hate MESA for how they do that and what they charge. I would only recomend that as it would be the simplest way for someone who wasn't savvy to getting them matched up by the tubestore or whoever. If MESA sells it, it will be fairly obvious that it should work.

MESA seems to use crap tubes a lot too. I went through 16 of their high end 12AX7 SPAX? tubes to find one that wasn't microphonic at my friends store once. Jeez...and they were 18 bucks a crack!!! unbelievable.

[Lesser Known God]

Re: Got new Tubes but having problems

Originally posted by Dreamland_Rebel:
don't you mean 6 6L6's
each 6L6 is roughly equivilant to 25 watts that why the 100 watters have 4 50 watters have 2 and T-recs have 6.

<font size="2" face="Verdana, Helvetica, sans-serif">Doh! Sorry... I meant 3 "Matched Pairs" heheheheh Thanks, I'll go change that real quick.

[raymo]

Re: Got new Tubes but having problems

Originally posted by Cleveland Metal:
Personally, I don't like the EH tubes at all. I use svetlanas, or I'd get whatever MESA sells for the app..

<font size="2" face="Verdana, Helvetica, sans-serif">Ya know I believe Svetlanas and Sovteks are combining and changing the Svets to be a lil more like Sovteks in builds and I guess changing the Sovteks to be a lil like Svets, just what I heard at another board I check.

[Twisteramps]

Re: Got new Tubes but having problems

Originally posted by chris_olson:
I'm not a tube guy, but I've heard that Mesa's are very finnicky about tubes, and that the best bet is to use MESA matched tubes. Just what I've heard - keep that in mind.

<font size="2" face="Verdana, Helvetica, sans-serif">Mesa's tubes come from a variety of sources - they don't make any - they just screen print em and match them to three different 'colors' or at least that's how they did it back in the day.

Groove Tubes does the same thing, but rates em in with 10 different numbers.

Also, most larger tube resellers can sell you a set of tubes already good to go even with Mesa's retarded bias setup. There is no reason to get stabbed in the wallet by Mesa, imho.

pete

[Cleveland Metal]

Re: Got new Tubes but having problems

Ya know I believe Svetlanas and Sovteks are combining and changing the Svets to be a lil more like Sovteks in builds and I guess changing the Sovteks to be a lil like Svets, just what I heard at another board I check.

<font size="2" face="Verdana, Helvetica, sans-serif">WOW, I really hope not. I love the Svets and HATE the Sovteks... I'll never own anoher sovtek tube if I can help it. I don't even like their preamp tubes.

[Twisteramps]

Re: Got new Tubes but having problems

Originally posted by Lesser Known God:
OK, I ordered all new tubes the other day. I ordered 5 Chinese 12AX7's (CH-12AX7A), 3 Electro-Harmonix 6L6's (EL-6L6GC), and 3 Electro-Harmonix Rectifier tubes (EH-5U4GB).

I proceeded to carefully replace all of the tubes and when I turned it on, it came on then turned off almost immediately. First thing I checked was the fuse and sure enough it blew. I just chalked that up to new tubes+old fuse=blown. Once I replaced the fuse it was fine.

Unfortunately, not only does it sound quite as good as the stock Mesa tubes, my BIGGEST problem is the Microphinics (I think that's what it is). I can't get natural feedback any more. If I try to carry a note until it feeds back naturally, It just turns into an uncontrollable squeal.

Any suggestions on how I can troubleshoot this problem?

<font size="2" face="Verdana, Helvetica, sans-serif">Why did you get THREE 6L6s?

First thing I'd do is swap out the power tubes. did the problem go away? then it's the new power tubes.

If not, put the new power tubes in, and change out the preamp tubes with the old ones. Did that solve it? then you likely have a microphonic preamp tube, and most likely V1.

If it's a microphonic tube - then do the following:

Move the preamp tubes around - mark each tube with it's position so you can move em back for troubleshooting, and swap say all tubes over one - V1 to V2, V2 to V3, last preamp tube to V1.

It's likely that V1 is the culprit, since it's usually the highest gain stage in an amp, and a tube that squeals there may do just fine elsewhere.

Also, have the amp biased by a good tech - mesa has the most craptacular setup I've ever seen. Have the amp biased properly for your power tubes, and then write down or remember what the power tubes were matched at. Last time I bought a bunch of power tubes, they had current draw in ma written on the box. This way, when it's time for new tubes, just get another set that draws the same current and you won't need to rebias. This is MUCH better than just sticking with the colors that mesa recommends, as it has a lot more leeway than a real bias job.

*whew* that was long. Email me at [email protected] if you need more info/whatever, or you can give me an email and I'll give you my phone number. We can figure it out pretty quickly I'll bet.

Pete

[Lesser Known God]

Re: Got new Tubes but having problems

Well, I commenced the troubleshooting last night. Oddly enough, the problem appears to be stemming from ALL of the Preamp tubes. I tried replacing them one at a time and It continued to have problems, but as soon as I replaced all of them with the original Mesa Tubes it stopped. One thing I DID notice is that the original Preamp tube in the v1 position (Closest to the Input jack and protected by an aluminum insert) is actually a Mesa SPAX7-A? Is it ok to replace this with a 12AX7?

[Soloist1]

Re: Got new Tubes but having problems

Yup. Any 12ax7 should work in there.

[Twisteramps]

Re: Got new Tubes but having problems

I'd say now try replacing the tubes one at a time from the 'new' pile into the amp with the remainder being boogie. You might have had two or more 'bad' or microphonic tubes.. Or the boogie preamp tubes are so worn that they aren't putting out as much gain as they should.

How's the amp sound with the different powertubes and the same preamp tubes?

btw, GET IT BIASED! [img]images/icons/grin.gif[/img]

Pete