Diezel herbert 6550 plates turning red

  • Thread starter Thread starter Jujutsu
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Jujutsu

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Hi everyones, first sorry for my english skill !
I got a problem with my new herbert.
I just bought it used a couple of mounts ago and i really love it.
Before i got a AXE FX ULTRA with VHT 2/90/2 it was really good until i try the herbert... WOW simply amazing. :rock:

When i bought it, it's come with used TAD EL34, but very used ! so i need to change it.
I try to make that mix (4x) EL34 & (2x) sovtek 6550WE, i heard that mix on you tubes and a lot of user recoomended it !

My problems when i put the 6550 in, the power tube plates turning red and the glass glow blue & we can smell the amp still burn !!! and is very very hot...
After only 2 mins i just stop the amp.
I tri the 6550 into differents socket position: 1&6, 2&5, 3&4 same problems.
I don't make the right bias adjustment for that kind of tube because the amp want to burn, so.
But when i put my KT88 or EL34 into the same socket of the 6550, everytings is perfect ! without biasing. :confused:

Another test then i made is, i got HI-FI amp MUSIC ANGEL XD 800MKIII, come with originaly KT88, so i just put the 6550 into it.
The plate are not turning red but still very hot to.

Can someone please help me, i just don't understand... :doh:
 
Dude... you need to bias your amp after EVERY tube change. The fact that a different pair of tubes is working without re-biasing is a function of luck, not design.
 
Leave the 34's in it and be happy.

But, if you feel the need to change them, you probably need to take it to an amp tech if you cannot understand what is happening, but here's what needs to be done. A 6550 is not a drop in replacement for a 34 in terms of bias supply or current. Fortunately, there is enough range in the bias adjustment to handle the 10V negative bias supply voltage change.

Back the bias screw all the way counter-clockwise for the pair you are changing to 6550's (inners/outers/tweeners). Turn the amp on with your bias meter connected and start adjusting the bias screw clockwise until you get the bias in the desired range. Remember, you are reading per duet on the Herbie, not per tube. For the 6550's, get it up to around 80-90 on the meter. Repeat for the next pair.

This is probably why the German government made Peter start putting all biasing apparatus inside the chassis.

Steve
 
Welcome to the board first.

Please shut down the amp !!! The 6550´s are
maxed out on the plate disappation. You have
to rebias the amp or better let the EL34´s in.

Best regards,
Peter
 
Hi peter, nice to meet you !
Thanks for the holy diezel... simply amazing !
You always talk about the RUBY EL34BHT, why this brand compare to others EL34 ?
I will need more informations about how biasing correctly the herbert, more details possible.
Thanks
Julien
 
Check on the Diezel website there is a tutorial on Biasing. I suggest you do so before fuckin' up your Herbert!!!
 
Nico":repf3f2f said:
Check on the Diezel website there is a tutorial on Biasing. I suggest you do so before fuckin' up your Herbert!!!
Click to expand...

THIS!!!

And do NOT turn it on until you know it's safe and well adjusted...!! Otherwise your beautiful Herbert may sustain some damage - not cool.

Peace,
V. :thumbsup:
 
HI guy thanks for everythings, but today i try to fix the bias with the EL34.
1) remove the fuse
2) plug amp with loaded speaker
3) set multimetter at 200mA (DCA) & plug it into the red-red & black-black
4) turn on the amp
NO fucking reading ! = 0mA it's impossible.
The only reading than i got is, in the scale of 20V (DCV) & is around 28,29,30.
Does some have an idea, thanks again.
 
Broken fuse inside the multimeter
or wrong measurement.

If Your tubes are glowing red, You will
have more than 200mA which causes
a broken fuse.
 
Thanks Peter & eveyones !
My multimeter was broken, i just buy another today and everythings goes well.
My amp work like a new one now, i try a blend of:
(2X) 6550WE sovtek with, bias @ 100.0 (4X) EL34, bias @ 62.0 = it's a good match !
But i prefer only EL34... like before.
Next week i'm gonna try some blend with KT88, 6550 & EL34... if some of you have make research about ?

Maybe this can help some others,
Herbert values in brackets

1) Remove the backpanel. You'll see three (four) jacks above the fuses.

2) Set your multimeter to 200 mA DC and plug your black probe into the black jack and the red to one of the red jacks.

3) Remove the jack-corresponding fuse from the fuse holder which is located on the backplate, turn volume controls to 0 and make shure a load or speaker is connected to the amp.

4) Now switch it on and read the bias current from your multimeter. Adjust it to the proper value by turning the bias pot which is accessible with a little flathead screwdriver through the hole in front of the red jack.

5) When finished, turn off the amp, install the fuse and repeat the same
steps for the other pair(s) by using the other red jack(s) and removing the other fuse(s).
 
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