Preamp issues mesa400+, also need retube recommendation

**garmenteros** · #1 05-24-2010, 05:30 PM

I have a nice mesa 400+ which I have with jj teslas in the power section and tungsols in the pre. Anyways friday I turned the amp on normally and when I hit the standby switch no output was coming through the speakers. No noise nothing, dead quiet, like if the standby switch was still on. I checked the back and all power tubes were glowing. The amp was wired correctly to the cab, 4ohms jack on the bottom left to 4ohms jack on my powerhouse cab. Turned of the amp and waited a while and switched speaker cables and used a 1/4 to speakon jack. Same result. So tech time. Upon opening the amp up everything looks fine, and no values have changed on the capacitors or filters, and voltage is still running normally through the amp. So we try some other 12a7s I borrowed and the amp is back to life... I try my tubes in another amp and theyre bad, making terrible noises and humming like hell...

I know some tubes can last 40yrs but some need changing... dont really understand why though... my fliptop worked fine with its stock tubes. What might cause pre tubes to go dead? I put the amp on standby before I turn it off, though sometimes I forget and just turn it off but I think this is ok... correct if I'm wrong... Sometimes I turn the amp on without the standby switch being on, dont know if this is an issue... I do hear some crackling noise from time to time doing this...

Also, what tubes are you guys running in your mesas? I thought tung sols were pretty good, I used the mesa branded tubes before but I took them out and put them in another amp...

**garmenteros** · #2 05-25-2010, 12:24 PM

to the top, could really use some input...

billhilly66 · #3 05-25-2010, 01:22 PM

I'm running the same tubes you had. JJ 6L6's and Tung Sol 12ax7's. I haven't had any issues so far and like that tube arrangement.

Caca de Kick · #4 05-25-2010, 06:52 PM

I'd look at pin fit issues between the different tubes. Maybe the sockets are too loose like the maybe the tungsols use skinnier pins?

jastacey · #5 05-25-2010, 07:03 PM

On the preamp tube issue ... the tubes that are currently made are not built like the tubes built in the 1950',60',70's ... those tubes have been known to last decades, the newer stuff is built to a different seemingly lower standard ... I to have had some of the newer Russian & JJ's go bad after 40- 50 hours .....

**garmenteros** · #6 05-25-2010, 10:42 PM

just bought 8 mullards, to have another set of preamp tubes as a backup... lets see how this goes...

mikeldtl · #7 05-26-2010, 01:26 AM

I went through the same issue. Blown phase inverter tube twice about 3 months apart. I was using JJ 12AX7 and popped the stock Mesa tube in and it has lasted me about 6 months now. All I can think of is that the JJ tubes didn't like the current draw to feed the power section and died prematurely. It's a strange day to put the 8 year old stock Chinese tube back in and play away waiting for it to go and..... nada.