290 dead: help me please!!!

hello to everybody..........with horror I realize my 290 is dead. a couple of hours ago I turned it on but when lifted the standby switch nothing happened. here's some signs:
- front lights are on (also deep extent light)
- tubes are not on, i.e. no lights
- front fuse good
- channel fuses are apparently ok

as far as my ignorance tells me I might have a dead transformer. this being the case, can you tell me what kind is it? I found this website but don't know what is the right one: http://www.beyondeleven.com/Mesa-Boogie-Amplifier-Transformers-s/547.htm?searching=Y&sort=5&cat=547&show=200&page=1

please, help me with this....I'm desperate.........

michael

Could be a short in the 12cable connector....open the top lid and take a look to the left back third....there´s a connector inside. Check if there´s burn marks, especially the green cables. That´s the 6.3V heater supply. If that´s shorted out for some reason your amp is dead quiet....

yep.. if I had to guess.. the gray tube heater wire is burnt at the connector.
I had this happen and sent it to Mesa. It's a known and somewhat common problem apparently. It's not the first time I've seen it mentioned on this board.

Here's a few shots of mine.



FYI.. if you open the amp to inspect it. Do not touch anything near the big blue cylindrical (battery-esque) looking things.
They can hold enough charge to end lives.

Mesa more or less cuts the connector out and soldered the wires directly to the board.

thank you a 1000 for your quick reply. in the meantime I had enquired to Mesa and they mentioned to me the following, along with the procedure to have the EL34 with the 6L6:

Hello there,

It sounds like you have the older 2/90 power amp made pre-2000. Those versions can run four 6l6's and four EL-34's at the same time, see the attached diagram for the proper tube placement.

The issue with your 2/90 not powering up the 6L6's is more than likely due to a failed transformer header connection and not actually a failed transformer. I have attached a written diagram that describes how to hardwire the transformer in place and bypass the actual header. This should resolve the issue without having to replace the transformer.

Hope this helps!

following is the diagram they emailed to me:



sorry but I don't know how to make it smaller. hope the moderator will fix it.

all the best

michael

p.s.: I'm heading now to the official mesa repair center for Italy cause I don't want to worsen the thing. will let you know

looks exactly like what we mentioned above....
Another option (if you don´t wanna have it all wired/soldered directly to the PCB) is to use high quality WAGO connectors like these:


I use them in both my 50/50 and 2:90....

gosh.....I'm breathing again: it was exactly what you guys mentioned. check the pics attached:



and further:



the first pic shows the connector divided. it was literally melted so the technician had to cut out and clean all the incinerated parts.

image 2 shows a piece of that connector..........

now that my 290 got back on track I read about the chance to have the EL34 with the 6L6. I have asked mesa to give me the right procedure. they told me that if the 290 I own is a pre 2000 one all I have to do is put the EL34 couple to the fartest left side and a couple to the fartest right side. How can I tell if my 290 is a pre 2000 one? I have s/n 3333...........

all the best and thanks for you precious help

michael

michaelmellner said:

now that my 290 got back on track I read about the chance to have the EL34 with the 6L6. I have asked mesa to give me the right procedure. they told me that if the 290 I own is a pre 2000 one all I have to do is put the EL34 couple to the fartest left side and a couple to the fartest right side. How can I tell if my 290 is a pre 2000 one? I have s/n 3333...........

all the best and thanks for you precious help

michael

Click to expand...

Yep. You can use EL 34's but only in certain sockets. I'm guessing the class A/B sockets and not the class A sockets.
This greatly depends on what revision of the 2:Ninety you have.
It would be best to consult Mesa on this. They sent me a diagram once and it was the outer sockets for my revision of the amp.
I never tried it though.

* x x *
* x x *

*=EL34
X=6L6

bjoneill74 said:

michaelmellner said:

now that my 290 got back on track I read about the chance to have the EL34 with the 6L6. I have asked mesa to give me the right procedure. they told me that if the 290 I own is a pre 2000 one all I have to do is put the EL34 couple to the fartest left side and a couple to the fartest right side. How can I tell if my 290 is a pre 2000 one? I have s/n 3333...........

all the best and thanks for you precious help

michael

Click to expand...

Yep. You can use EL 34's but only in certain sockets. I'm guessing the class A/B sockets and not the class A sockets.
This greatly depends on what revision of the 2:Ninety you have.
It would be best to consult Mesa on this. They sent me a diagram once and it was the outer sockets for my revision of the amp.
I never tried it though.

* x x *
* x x *

*=EL34
X=6L6

Click to expand...

It´s actually the Class A sockets that can run with EL34s. On the V1 (blue pilot light) it´s the outer pair of sockets on each side....
Here´s some pics that were confirmed by Mesa:

thanks again to everyone partecipating on this thread: you have been wonderful.

as regarding to the EL34.............I got a reply from mesa about my serial number. they told me my 290 was shipped from factory some 16 years ago, in 1996.....gosh time passes quickly!

so, this put my amp in the pre 2000 version thus the EL34 will be put at the extreme sides of the tubes, as in version 1. besides, I was looking at the blue pilot light thing. mine is this but has no pilot light although it is blue. I guess the 290 housed the pilot light only in US versions.

here's the pic of mine:



now on the tubes.
sorry for my ignorance but do I have to install coupled EL34 or else? and do I have to regulate the BIAS? I used to know the 290 doesn't need any BIAS regulation but mixing ELs and 6L6s is another story..........

mic

EDIT:
a word on the choice of the tube combination: what is your experience and comment. does the sound really improve?
I found this web site with some explanation on the various combination.
https://ssl.eurotubes.com/cart/index.php?page=view_products&category_id=6&sub_category_id=57

of course I'm not linked in any way with this reseller. I just want to check about the comment on the tubes choice

The Bias in the 2:90 (as in any other Mesa amp) is set at a fixed value.
Now if you go shopping for new tubes you just tell the vendor (and that´s why I would shop at a real tube specialist and not Thomann, or any normal music store...) what kinda amp the tubes are for.
As for Europe, I can highly recommend Tube-Town in Germany, they also ship all accross Europe. (I´m in no way affiliated or connected with this store or whatsoever.....)

When you swap/change the tubes in your 2:90 I would do a full retube (now that´s again just me....). But especially when going to an integrated set of EL34/6L6 I would make sure that the bias draw on each channel is the same.
Also, change the 1 driver 12AX7 as well as both phase inverter 12AX7

What brand is the big question....some will say EH, other swear by JJs, lots of folks say =C='s is the way to go. And that´s wher all of it gets very subjective...
I have found an integrated set of TungSol EL34B and TungSol 6L6GC-STR with 3 Tube-Town E83CC to be my personal favorite for the 2:90 (as well as *affordable*, especially over here in Europe....)

This is just my 2 €-cents

thanks for you reply. I just sent tube town a request for advice on retubing the 290. will see what they tell me..........I enquired to Eurotown as well and to Doug Tubes, which I bought my first retubing from. I bought ruby tube that time.............

michael

Your amp has the blue pilot light.
It's between the power and standby switches.

As for tubes.. I'd probably stick with Mesa tubes.
If your Mesa amp has a problem when used with Mesa tubes.. they cover any problems up to a certain amount of time.

You'll want them matched pairs just as you would normally.
The Mesa amps are fixed bias.