Sudden channel power loss

[plapnab]

I just bought a Mesa Boogie Dual Rectifier off of ebay a about a week ago. It worked great when it arrived. However, after the second day of playing it I had an abrupt loss of power in channels 2 and 3. Channel 1 works fine. There is some sounding coming out of 2 and 3 and they seem to be working but like I said the volume is minimal at best. Does anyone have an idea whats going on here??? Did some of the tubes go bad???

 

[fluff191]

When that happened to my Recto it turned out to be a bad power tube. Playing the clean channel you would never know anything was wrong.

I would just replace all 4 power tubes.

 

[thunda1216]

I just bought a Mesa Boogie Dual Rectifier off of ebay a about a week ago. It worked great when it arrived. However, after the second day of playing it I had an abrupt loss of power in channels 2 and 3. Channel 1 works fine. There is some sounding coming out of 2 and 3 and they seem to be working but like I said the volume is minimal at best. Does anyone have an idea whats going on here??? Did some of the tubes go bad???

before freaking out, check the cable from your foot switch to the amp.

ty

 

[plapnab]

I took a good look at the tubes and one of the 5U4GB's looks like it went bad. There is a bluish haze around the bottom of the glass and the inside wiring looks charred. Hopefully, that's all the problem is...I'll know Friday as I have to make a two hour drive to the nearest Boogie dealer...big gig Saturday can't wait to order parts. Thanks everyone for your replies they were very helpful www.roxburydrive.com.

 

[fluff191]

I took a good look at the tubes and one of the 5U4GB's looks like it went bad. There is a bluish haze around the bottom of the glass and the inside wiring looks charred. Hopefully, that's all the problem is...I'll know Friday as I have to make a two hour drive to the nearest Boogie dealer...big gig Saturday can't wait to order parts. Thanks everyone for your replies they were very helpful http://www.roxburydrive.com.

Why dont you just test it now by flipping it over to the silicone diodes and bypass the rectifier tubes? That will tell you right away if its the rectifier tubes.

 

[plapnab]

No, that didn't do much. I got a little more sound but not much more. Clean channel is fine. You said yours did the same thing...when you switched to the diodes did that work for you?

 

[plapnab]

Just got off the phone with a Mesa Boogie tech support rep...said it is definitly a tube problem. Specifically, the 12AX7 that control the power to the preamp. He said as long as it's powering up it should be just that and not to worry. So, my brain isn't spinning so bad now...cool beans!

 

[fluff191]

No, that didn't do much. I got a little more sound but not much more. Clean channel is fine. You said yours did the same thing...when you switched to the diodes did that work for you?

The first time it was a bad preamp tube, the second time was the power tubes I had just installed were rated wrong and were running very very cold, so cold that I had about half volume on the 2nd and 3rd channel.

 

[plapnab]

It was the 3rd 12AX-7 tube that went bad. Put a new one in and it fired right back up!

 

[laurens]

It was the 3rd 12AX-7 tube that went bad. Put a new one in and it fired right back up!

How did you find it? Did you take a new one and swapped it in all positions or else ?

 

[plapnab]

Called Mesa Tech support and they explained to me what each preamp tube is for. For that specific issue the tech was about 99% sure it was #3. However, he said buy a new tube and go through 1 -3 just in case. Long story short #3 was bad. Happy camper now