Problem with herbert :-(

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xchrisloungex

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Hi guys,

Had my second band practice last night with the herbert since buying it and came up against a small problem. When using channel 3 there is a huge amount of hum that i cannot get rid of. On channel 1 and 2 everything is fine , no problems at all. Would this be a pre tube issue do you think?

Any help would be greatly appreciated as i'm booked to enter the studio with my band on monday which is worrying me as i was looking forward to hearing this monster on record.

Thanks alot

Chris
 
Is there anything in its loop?

Yes, pull it.

No: swap V2 and V5. V1 is closest to the amp's input jack.

Herbert:

V1 Used by all channels

V2 Used by channel 3

V3 Used by all channels

V4 Mixer & Loop Driver

V5 Return Driver

V6 Phase Inverter
 
No there's nothing in the loop so I will try swapping the tubes in those positions. Thanks alot for your speedy reply, hopefully it will solve the issue.

Chris
 
Maybe it would be even better to swap V2 and V1 - if it is the tube you'd also hear it on channel 2 (and get new tubes then of course) . . .
 
Thanks Peter! (and you duesentrieb ;) )

This is one of the many reasons I decided to go with a diezel. The ability to ask the man in charge any question that you need to know the answer of, and the willingness that you show in answering questions from customers is out of this world.

I will try this when i get back to the practice spot on monday and let you know if this solves the problem.

Chris
 
right,

I bought two high grade pre's for v1 and v2 and 2 of the exact same tubes that were shipped with the herbie for v3 and v4 and still the problem continues. I'm so frustrated as i've only used this amp three times for around 2 hours a time and i'm due to record a demo with my band as of monday but the hum on channel three is still present and hard to ignore. I don't know what to do now as sending my one week old herbert back to germany is not going to be possible till payday (4 weeks from now) as i've exhausted all my funds on the amp itself.

I took a video on my phone to show just how bad this problem is and will try to post it tomorrow to see if there are any alternatives to shipping my amp back.

Chris
 
Pull the powerubes pairwise to see if it goes away.
1/6
2/5
3/4

For each pulled pair run your cab into a speaker out one step below its impedance.
16 Ohm cab --> 8 Ohm speaker out
 
Unfortunatly it's goig to be too late to do anything before the studio as it's kept at the practice spot and i won't be able to get there in time :( .Looks like i'll have to sort something else out to use in the studio. Anyway, heres the vid i took on my phone last night after replacing the pre tubes. When you see me change the settings i'm simply putting all knobs to 12 o clock so you can see that it's not just some drastic settings that i have on channel three. Looks like i don't have much luck with tube amps, my bogner blew a tube the first time i used it although the supplier did give me a full a retube which helped ease the pain a little but i then sold that to get my dream amp (the herbert) and it happens again haha. typical :cry:

http://s4.photobucket.com/albums/y118/xchrisloungex/?action=view&current=31012008002.flv

Chris
 
The hum is in all channels, just amplified more in ch3.

I had the same prob with one of my DIY amps (after a friend of mine tested it before I will send it to another friend) yesterday - just one EL34 was loose in its socket and caused it. Pushing it back into it cured everything.

Try to get to the amp and pull the EL34s pairwise - thats all I can think about in the moment . . .
 
thank you duesentrieb!

I will have to give this a ago when i get into the studio on monday as i honestly cannot get to my amp till then. Hopefully that is all thats is worng. However when you say pull the tubes in pairs you mean the two outer power tubes first then work my way inwards?

Also the hum on channel 1 and 2 doesnt actually seem that bad in person even though the cam makes it sound pretty bad. Am i right in thinking that on channel 1 there should be little to no hum?

Chris
 
First pull outer.
Hum goes away - play like this (with a pulled pair) - set impedance one step down

If hum persists: pull inner (put back outer)
Hum goes away - play like this (with a pulled pair) - set impedance one step down

If hum persists: pull in betweens (2 + 5)
Hum goes away - play like this (with a pulled pair) - set impedance one step down

You hear how the hum increases from ch2 to ch3. Thats part of the huge amplification factor of ch3. Its still in ch2 (seems logical to me)
 
and is that safe to play with a pulled pair for a long period (obv with the impedence one step down) or simply to test for the problem tube?
 
Thats safe. Has been done for decades with Marshalls . . .
 
once again mate thanks for your help! will give this a go.
 
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