Dual Rectifier Reborn Multi Watt Channel 3 Vol Cut Problem

[adamCGCFAD]

Hello,

I recently purchased a used Mesa Boogie Dual Rectifier Reborn Multi Watt.

It was working perfectly for two weeks, then during my first band rehearsal I encountered a problem with Channel 3.

The volume will suddenly cut to about 50%, then jump back up to normal vol randomly. It will make a cracking sound before the volume cuts up or down.

(It is not a gradual volume fade, it is either an instant cut down to 50% or jump up to normal.)

If I change channels then go back to 3 it will sometimes go back to normal vol then cut down again after a couple of seconds.

Channel 1 + 2 are perfect, they sound awesome, I've had to just use it as a 2 channel amp in rehearsal for now.

I have checked and confirmed all cables and guitars are working correctly.

Has anyone encountered this and what are the possible solutions?

Thank you,

Adam

 

[adamCGCFAD]

So I was advised by Mesa tech support to change the pre amp valves,

5 new Mesa/Boogie 12ax7's arrived today,

I have installed them,

I am now £87.50 poorer, and still Channel 3 is faulty.

SO gutted!

Anyone else experienced this??

 

[afu]

Does it do it in all modes? What are your standard settings for mode, power, and rectifier?

From my experience, a volume cut like that is a poor connection. Oxidation on the tube sockets could do it, but I'm curious about why it only happens on channel 3. If 3 is Modern, the negative feedback is disconnected. If you switch to Vintage and it doesn't happen, something is really wrong. The tubes for the phase inverter at V4 could use a look.

 

[adamCGCFAD]

Thanks for the reply!

Channel 1 + 2 are working perfectly,

Got my rear settings at Diode and Bold,

Front settings at 100w and Modern.

I have tried all combinations of Diode/Valve Rectifier Spongy/Bold Raw/Vintage/Modern 50w/100w etc

All tubes are Mesa branded and in perfect working order,

I purchased some more new Mesa tubes and put them in and it hasn't fixed the problem.

It does sound like a loose connection of some sort due to the sudden cutting of volume.

I'm currently speaking to tech support at Westside Distribution (Mesa/Boogie UK Distributor), they're going to reccomend a local tech.

I will keep you updated on the outcome.

 

[Blaklynx]

So I was advised by Mesa tech support to change the pre amp valves,

5 new Mesa/Boogie 12ax7's arrived today,

I have installed them,

I am now £87.50 poorer, and still Channel 3 is faulty.

SO gutted!

Anyone else experienced this??

Never mind, use them as spares.

I would've thought the UK tubes would be significantly cheaper. What can I say here in Australia? Mesa's are around AU$55!!ea (another great AU rip-off). 5x$55 is AU$275!! It's a bl**dy ripoff and Mesa should look into this. To me it affects their brand image as 'the great big ripoff'.... even their amps are very expensive here.

According to XE currency converter from UK to AU, that's AU$184.00 for your tube cost, significantly cheaper at your end.

Preamp valves here range from around AU$18-22 for JJ's, EHX and Sovtek, around AU$25-35 for Mullard and Tungsol.

If I remember correctly, Mesa preamp tubes are rebranded JJ's anyway.

You could've bought any brand 12ax7's to test. Preamp tubes don't really matter in terms of matching or brands but you need to use Chinese made preamp tubes in the cathode follower positions (search forum or google) or premature failure will occur in those positions. As a simple general rule, the JJ's are OK in those positions.

For the power tubes, they have to be matched and need to be in the correct bias range for your amp. HINT: Jump on-line and buy other brand power tubes from reputable dealers; just tell them what amp it's for and they'll send you ones for your amp.

I currently use TAD EL34B's in my Roadster that I bought from a reputable dealer off ebay located here in my state.

As for your channel 3 issues, I can't really say, but did you see this post? http://forum.grailtone.com/viewtopic.php?f=24&t=69319
You may want to PM the guy and ask what the solution was.

Also found:
http://www.seymourduncan.com/forum/showthread.php?227141-MESA-Dual-Rectifier-Troubleshooting
I thought the second post was interesting.

-B

 

[adamCGCFAD]

Ouch, and I thought I was being ripped off.

I did originally put in some of my spare EHX 12ax7's in, no change in Channel 3.

The Mesa Boogie tech guy said I had to use Mesa Branded tubes only for fault finding so I went ahead and purchased some,

What an excellent sales technique!

I will PM that guy with the similar problem,

Thanks for the reply

 

[deeman]

It is good to have a known good preamp tube to troubleshoot issues. I would have just tried purchasing one or two new preamp tubes and replaced one at a time. Who knows if the new preamp tube you put in is also not working. Couldn't hurt to replace one-by-one to make sure.

 

[adamCGCFAD]

Yes I tested each tube one by one with 5 of my spare EHX 12ax7's, then with 5 new Mesa 12ax7's

Unfortunately it didn't solve the problem.

Unless all ten tubes were faulty, who knows?

It'll be with the Mesa UK repair centre on Monday, I will let you guys know the outcome.

Thanks,