Another " problem with my dual rec " post

[Familia><Publica]

Hi everyone, new to this forum. I Just got an eq pedal, so i'm using the effects loop for the first time. Switching it on at the back has made the amp noisy as hell, white noise amongst other noise and thats even without the pedal plugged in. whats up with that? Why does the amp only make noise with the effects loop on? Any ideas ? I thought a tube problem perhaps, but surely it would affect the amp whether the loop was on or not.

Update: Just fiddling at the back and turned the vacuum/diode switch from diode to vacuum and the noise went almost silent ( even with fx loop on which i thought the noise was coming from), the bold/spongy switch also effected the noise when i switched between the two ( but not nearly as much). Upon switching the amp back to silicon diode, the amp has now shut itself off. Looked at the fuse in the amp, seems it has blown. But the question is, why has it blown? something serious i feel. Again i say, if it was a tube problem, why would diode/vacuum, bold/spungy, fx loop on/off make a difference in noise/hum/crackle e.t.c

Sorry about the long and compicated post, hope someone can help, thanks.

 

[Platypus]

Preamp tube V4 controls the FX loop on the Dual Rec and would most likely explain the noise... until you said switching to tube rectifier mode stopped the sound.. that is bizarre.. someone who is more familiar with the technical side should be able to help you here but I would guess V4 Preamp tube needs to be replaced.

 

[jbird]

Rectifier tubes :idea: Maybe a full re-tube :?:

 

[Familia><Publica]

Well, i forgot to mention, that when the fuse blew, i was behind the amp at the time and had all tubes in view. I didnt see any of them arc, lightning go off inside e.t.c they looked normal and faded as the fuse blew.

 

[Platypus]

Well, i forgot to mention, that when the fuse blew, i was behind the amp at the time and had all tubes in view. I didnt see any of them arc, lightning go off inside e.t.c they looked normal and faded as the fuse blew.

Do you still have your covers on the preamp tubes? I'm guessing the culprit is V4.

 

[Familia><Publica]

Yeah, still got the covers on them. Wasnt aware that they could arc/lightning e.t.c the same way power tubes do? and can preamp tubes blow fuses?

 

[jbird]

Usually, a blown fuse is caused by a short. Replace the fuse and tubes. If the problem persists, it's time for an authorized repair shop. Most probems come back to the tubes!

 

[Familia><Publica]

The fuse blew when switching between diode/vacuum, bold/spungy. Cant pin point the exact moment. Should i be switching between these when the amp is off ? maybe switching between them caused a surge. Ive heard of two similiar problems with people switching between similiar settings and blowing fuses.

Two quotes from other people ( one amp being a heart breaker )

"At the first rehearsal, it blew a fuse when I switched from the "Tweed" setting to the "Full Power" setting. Replaced the fuse, and about an hour later, it blew another fuse. I thought, "faulty Power tube?" and replaced the tubes with some old Sylvania 6L6's, turned on the amp, almost NO sound output! I put the stock Mesa tubes back in it and have had no further problems."

"I've blown a fuse before too when switching between the silicon diode/vacuum tube and the bold/spongy settings. I never figured out why it blew or what exactly happened. The amp repair dude told me it was a huge problem but I bought 2 new fuses and finished recording guitar that day and it's never happened again. "