New Tubes, Roadster Died. Ideas??

[fuhnetikunion]

Bear with me. I just want you to be fully informed first.

I've had my Mesa Roadster since February of 2007 and it has been a wonderful workhorse. Usually many times a week. It has more than paid for itself throughout the years and has treated me well...

...until today.

I ordered a full retube kit last week from Doug at Dougstubes.com consisting of Ruby 6l6 (quad), Electro Harmonix 5U4G(x2), and Tung-sol, JJ, Penta Labs, and Sovtek 12ax7's. Today, I removed the chassis and the original Mesa tubes and cleaned the whole top side. I then installed the preamp tubes individually in the order Doug suggested as a starting point (T-S, JJ, PL, PL, PL, S). I carefully seated all the tubes and reinstalled the spring covers. Next, I installed the Power and Rectifier tubes snug in their sockets and tightened the metal clasps.

After double checking everything, I powered the amp on and let it sit for twenty minutes. The tubes all lit up and things seemed to be going fine. I plugged the amp into the cabinet and the guitar into the amp. With master volume and guitar volume down, I switched off standby. The fx loop LED lit up on the front of the chassis, though the fx loop was NOT activated, and there was no sound. Since the chassis was still out and easily visible, I was able to see what looked like a blue "pulse" through the power tubes and I immediately switched to standby and then OFF. I waited five minutes and then retried powering it up. Again, fx loop light on, no sound other than a random pop every now and then. The pops seemed to coincide with the "pulses". Even when you hard bypass the loop, the light is ON on the front. The footswitch changes channels and features, and when you step on FX LOOP, the light gets slightly brighter, and then just barely dims when you turn it OFF.

Thinking there might be a bad tube, and being without meter, I removed the all of the new tubes and reinstalled the Original Mesa tubes. Same problem. FX LOOP light on, no sound from amp. The amp was working perfectly three days ago at a gig and now won't even work with the old tubes. My heart is breaking by the minute. I've loved this amp since day one. I just wanted to liven it up, and it seems I've failed.

Does any one have any advice/direction for a brother in need?? Mesa's have fixed bias, and the switch is set properly. Could new tubes have fried my baby?? Nothing visibly arced and the power supply was removed during the install. Nothing looks fried anywhere that I can see.

Thanks for reading. I hate my first post had to be this.

 

[pinhedgtr]

Hey there and welcome!
I was wondering, did you say you turned the amp on and then plugged in the speaker? I'm not sure if that will damage your transformer if it's on stand by, but it's always better to plug your cab in before you power up. I dunno of a way to check that, maybe one of the vets here can help with that.
If that's not the problem, I would think it has something to do with your new tubes, since it worked fine before you changed them. Did you put your old power tubes back in as well?
Definitely do a search for Mesa roadster fx loop light cause I think I've heard of this issue before.

Good luck man!
Brian

 

[elvis]

Bummer.

Doubt that tubes would cause a malfunction with the loop. If the loop is on, and you don;t have anything plugged into the loop, I wonder if it would have no sound. Try a cable from FX send to return (assuming it's a parallel loop).

The output tranny should be fine as long as the amp was in standby when there was no cab plugged in.

I would guess that something went bad due to the pulling of the chassis or the cleaning. What did you clean with, and did you clean any pcboard circuitry or pots or switches?

You also may have inadvertantly changed a setting switch or knob. Roadsters are pretty complicated - did you check all the settings?

 

[shytfayse]

You also may have inadvertantly changed a setting switch or knob. Roadsters are pretty complicated - did you check all the settings?

+1

Make sure the effects send is at 50% and not at 0%. Another common switch bump is the 6L6/EL34 bias switch which will be a problem since you are using 6L6's.

Good luck, Pat.

 

[fuhnetikunion]

Hey guys,
Thanks for the suggestions! After posting here, I discovered that a musician friend I know just happens to be a newly certified Mesa technician... one of only a couple in the state of NC! I took the amp to him and let him do his work. He discovered that I had two resistors that had burned up. Though he can only speculate as to the actual reason for the burn up, he attributes it to the cathode follower circuit that stresses v3 and v5, with the main problem being in v5.

He replaced the two resistors, checked the new tubes, and then installed everything. I used a retube kit from dougstubes.com that had Penta Labs 12ax7's in v3-v5, so we replaced these with Mesa brand tubes since, regardless of original manufacturer, they are all tested for proper voltage handling. He now has the amp up and running, but the FX light is still on. I JUST sent him troubleshooting directions on how to make sure the controls are set properly and an waiting on his reply.

he did divulge that this was a very uncommon occurrence. All things taken into account, I should have my asp back by Thursday.

Thanks again for all the great suggestions. I'll be sticking around here.