Markbass Classic 300 tube help

iamdenialNJ · #1 09-19-2010, 10:34 PM

Hello, just recently acquired a markbass classic 300 head and it has some pretty good tube tone coming out of this thing but the lcd reads 'v6 tube failure'. now...when the amp is turned on the anterior 3 tubes do not glow like the posterior 3 tubes. I have re sat all of them in different places and it seems like all tubes glow when they are sat in the posterior 2 tube sockets. The preamp tubes all look to be glowing correctly. When I pulled the power tubes out 4 out of 6 power tubes seemed to have loose material inside the tube (metallic pieces, dust? dirt?) The amp works fine but I really have to push the preamp and the master knob pretty high (around 2pm) to get bedroom playing levels. I really want to reorder some new tubes but I want to figure out what the problem is. I feel a visit to an amp tech is imminent. Someone please help my amp! Thanks and I appreciate any answers ahead of time.

posterior of the amp
O O O
O O O <---these three sockets do not seem to work
anterior of the amp

JimmyM · #2 09-19-2010, 10:49 PM

first thing i'd check is the tube in the v6 position.

iamdenialNJ · #3 09-19-2010, 10:53 PM

Which would be which socket (the manual doesn't say anything about tube positions etc)? I've resat all six tubes in all six positions and it seems like I've isolated the problem to the tube sockets themselves...

will33 · #4 09-19-2010, 11:39 PM

Quote:

Originally Posted by iamdenialNJ

When I pulled the power tubes out 4 out of 6 power tubes seemed to have loose material inside the tube (metallic pieces, dust? dirt?)

This could be a problem.....but there is reason why they are failing. 3 out of the 6 sockets seems weird too. Higher power tube amps are usually class A/B. Power tubes work together in pairs. Having the back 3 work and the front 3 not points to another internal problem. Maybe a "fork in the road" in the circuitry and the bridge washed out? Getting beyond my expertise here.....

iamdenialNJ · #5 09-20-2010, 12:15 AM

Yeah...I'm thinking amp tech time. It's going to suck not having an amp. I'll see if I can borrow my friends in the meantime...

rodl2005 · #6 09-20-2010, 12:56 AM

AFAIK the SVTII of mine runs 'em in 2 lotsa 3 pwr tubes. AS always I could be off tilt.... /
& still...... tech time- pity---U could try & PM Peter Murray on here- he's the USA Mark Bass man!!!

Didn't these amp diagnose themselves, repair 'emselves & then make U a calming cup of green tea?? ;-)

Sorry...............

iamdenialNJ · #7 09-20-2010, 12:59 AM

Yeah...that's why I'm thinking about buying some new tubes and trying them out because this amp is supposed to "fix" itself thus leading to fewer repairs.

MIJ-VI · #8 09-20-2010, 01:10 AM

Please contact Markbass for advice on how to proceed.

There's no point in taking unnecessary risks.

iamdenialNJ · #9 09-20-2010, 01:15 AM

markbass has not answered yet. i'm going to send them another message.

MIJ-VI · #10 09-20-2010, 01:18 AM

Peter Murray (Promotion/Marketing/AR, Markbass)
http://www.talkbass.com/forum/member.php?u=65788

iamdenialNJ · #11 09-20-2010, 01:50 AM

thanks for the link. let's see what peter has to say...

MIJ-VI · #12 09-20-2010, 02:04 AM

Please keep us posted.

rodl2005 · #13 09-20-2010, 06:08 PM

+1 do keep us posted!!!! Even if it DOESN'T make U geen tea, I'd love to know how this amp goes & hope it does well.

I'd DEF. suggest pro help- no sense buying new tubes... etc.

iamdenialNJ · #14 09-20-2010, 08:59 PM

Will do. I'm already planning a trip to the amp tech on thursday so we'll see...$50 bench mark fee which is only to diagnose the problem. Insane. I think I should rethink my career..

MIJ-VI · #15 09-20-2010, 09:06 PM

What did the folks at Markbass have to say?

iamdenialNJ · #16 09-20-2010, 09:30 PM

No answer yet..

MIJ-VI · #17 09-20-2010, 09:44 PM

Quote:

Originally Posted by iamdenialNJ

No answer yet..

Did you PM Peter Murray?

His Last Activity: Today 02:12 PM
http://www.talkbass.com/forum/member.php?u=65788

Did you send him an e-mail via his TalkBass profile?

iamdenialNJ · #18 09-20-2010, 09:59 PM

Yes, he sent me a message back saying that I needed to send him the question to his email account, which I have. This was yesterday. I'll give it another day...or two..

rodl2005 · #19 09-20-2010, 11:24 PM

Ya'd think it'd be in THEIR BEST interest to get this solved as quickly & painlessly as possibly wouldn't it???
Dunno whether these amps have sold in their thoasands like the LMII etc..... & good publicity on them would be HANDY me thinks.

Hope all goes well 4 ya. & thanx for keeping us in the loop, & keep it up!
Cheers.

seamonkey · #20 09-20-2010, 11:34 PM

The manual is at their site.
http://www.markbass.it/risorse/allegato_pro.php?id=89
It biases the tubes every time you turn it on.
Just change them out and I bet all is fine.
Chances are that unless you take it to a Markbass certified amp repair shop the tech won't know a thing about it - and shotgun it by changing tubes anyhow.