Dual Rec Cutting Out

[engulfedinlies]

The past couple of days I have cranked it up, and then all of a sudden it would just cut out (not entirely, but just a lot quieter) all the tubes were replaced about a month ago, and this just started happening. I checked all my cables and numerous other cables, and it would stay loud for about 4-5 seconds, and then cut out. Let me know if you have any suggestions on what the problem may be. (could it be the amp input jack, or speaker outs, or the tubes?) Thanks.

 

[Platypus]

What do you mean cut out? Do you mean the sounds fades or sputters out and then comes back a few seconds later?

If that describes your problem, try replacing your rectifier tubes.

 

[engulfedinlies]

the sound fades, and then if i turn standby off, and back on a few seconds later, it does the same thing. 4-5 seconds later it fades. my rectifier tubes look alright, but is there any tell tale sign that the problem is there?

 

[Platypus]

the sound fades, and then if i turn standby off, and back on a few seconds later, it does the same thing. 4-5 seconds later it fades. my rectifier tubes look alright, but is there any tell tale sign that the problem is there?

This sounds preamp related if it doesn't come back at all.. check your V5 phase inverter tube and your V1 as well.. any of those 5 could be your culprit but I would test those first. For grins, try switching to diode rectifiers if you haven't yet to try and isolate the problem.

Follow the tube testing guide in your manual or click the FAQ link in my signature to read up a bit on the topic, if you still have problems or questions that need clarifying post back here and let us know!

good luck

 

[engulfedinlies]

what does the dual rec take as preamp tubes? just 5 12AX7's?

 

[disassembled]

what does the dual rec take as preamp tubes? just 5 12AX7's?

Which version of the dual rec? Did you retube the amp a month ago?

Greg

 

[Platypus]

what does the dual rec take as preamp tubes? just 5 12AX7's?

Which version of the dual rec? Did you retube the amp a month ago?

Greg

Haha.. I had the same red flag go up in my head.

 

[engulfedinlies]

Sorry. it's a 3 channel Dual Rec. I replaced the 4 EL34's and the 2 5U4GB about a month ago. I didn't replace the preamp tubes, so i guess it is in need for a change. I ordered 5 new 12AX7's from Mesa, so hopefully that solves the problem.

 

[Platypus]

Sorry. it's a 3 channel Dual Rec. I replaced the 4 EL34's and the 2 5U4GB about a month ago. I didn't replace the preamp tubes, so i guess it is in need for a change. I ordered 5 new 12AX7's from Mesa, so hopefully that solves the problem.

Did you change the bias switch to EL34 when you swapped power tubes?

I think the preamp tubes will fix your problem.

 

[engulfedinlies]

yea. i switched it to EL34. thanks for all the help. i really appreciate it.

 

[Platypus]

yea. i switched it to EL34. thanks for all the help. i really appreciate it.

No worries man, hope you're back up and running soon!

FYI since you never changed your preamp tubes, they're covered in a metal casing (give it a half turn to the left and it should pop right off).

 

[boogieman75]

Similar situation with my DR. I purchased it around 2004. After 3 hours of heavy practice it cut out. I took it back to the dealer and they gave me a mesa 12ax7 preamp to swap out if it happened again...and it did. I tried to find the culprit and was unsuccessfull. I took the head back and they ran an O scope on it and could not get it to act up. The 3rd time I brought it in they ran another O scope, opened it up and found a "bare" wire that was just laying in side and the tech said when the amp started the cook, the bare wire would heat up and short something out.

Ever since they pulled the bare wire out, i have had no problems since.

Prolly happened when they stripped out the excess wires.