MESA Dual Rectifier Troubleshooting

Destructone

Destructone

New member
Calling all tone-gurus!

Just having a little problem with my Dual rec head.

I went to turn my amp on today and only the clean channel (ch 1) is working. whenever i switch to channel 2 or 3... its dead silent.

My suspicion is a preamp tube failure? If im right, does anybody know exactly which preamp tube is the culprit?

...or could it be a power tube failure?

any help would be much appreciated!
 
Re: MESA Dual Rectifier Troubleshooting

I'd start with V2 & V3 and throw in some known good tubes. Be prepared for the possibility that it won't solve the problem though...the number 1 failure mode in Mesa amps is the mute circuit in the channel switching network. The J-FET that mutes Channels 2 & 3 is the most like one to go. There's also a zener in there that can collapse (jumping the J-FET) and cause it to go silent. It's in there to protect the J-FET but it also adds diode clipping to the tone...and yes, Boogies have diode clipping.

Don't attempt to fix the mute circuit yourself...take it to a tech. It's hard enough to find let alone repair without tearing up other stuff.
 
Re: MESA Dual Rectifier Troubleshooting

Dumb as it may sound, but be sure the fx loop is off or, if you're using the fx loop, be sure the fx send level (vol) is turned up.

I don't use my fx loop, so I keep the send level down (off). If you press the fx button on the footswitch or amp, you get no sound.


Good luck.
 
Re: MESA Dual Rectifier Troubleshooting

Dead pots for for master volume control on both channles?

I had the exact opposite problem with my Dual last summer. My Chan 1 was dead silent unless i turned it all the way up and at that it was barely a whisper. Channels 2 and 3 were just fine.

Tech said it was the pot for the master on Chan 1.
 
Re: MESA Dual Rectifier Troubleshooting

Is solo engaged and you have that volume turned all the way down?
 
Re: MESA Dual Rectifier Troubleshooting

thanks for all the replies. turns out, it was just a blown preamp tube as I suspected... it was the V1 tube (valve closest to the input jack).

I wanted to just try a mere $15 test first before I took the head to a tech. Funny that the sales guy who sold me the tube assumed the same thing about the mute circuit and dead pots. I guess these are common mesa boogie problems.

thanks for all the help guys.
 
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