procedure for biasing a Herbert

[Capulin Overdrive]

haven't found a step by step for biasing a Herbert yet?


says to pull a fuse and then check the ma's?


do you pull the fuse with the amp on, and off standby?


are the bias pots in the black rubber slots next to the 3 reds?


and what about plate voltage? do you just call it 470 volts, and adjust the ma's accordingly for tube type?


can you get a plate voltage reading without pulling the chassis?


would it be better to pull the chassis and use a Bias Rite?

 

[demoncleaner]

I have the power off to on the amp. Then pull the fuse to the set that I will be biasing.

Put the black lead of the MM to the far right black port and the red lead in the red port to which you will be biasing.

With the amp on and standby set to run (master volume all the way to 0!) have a mini flat head screwdriver inside the rubber slot to adjust the pots. Also be sure the MM is set to DC current.

Look at the online manual for the mA bias setting for the tube type you are using. Multiply this by 2 as the manual is just for 1 tube and you are biasing the pair.

Once you are at the right reading, turn the amp off (standby and power). Take the MM lead out of the red slot and put the fuse back in.

Repeat for each pair.

 

[shadow070]

I never biased before but i think it should be like this:

Remove back panal
remove the tube
put new tube (should this be in pairs or only the one youre bussy with?)
set multimeter and connect pins
make sure cab is connected
turn amp on
switch stanby after a view minutes
bias the tube
switch standby again
repeat with other pair

Is this correct?

 

[duesentrieb]

And every now and then its cool to have a look at the official site. I've added biasing procedures for all Diezels when the site was launched two years ago. See "tech".

Let me know if you have further questions.

Plate voltage is 480 V. Even if you should have 475 (delta = 1.x %) you can be sure that different locations will cause a bigger delta for the prim. - and matched tubes have a delta of a bigger percentage - say they are within a 3mA range thats 5-10%.

 

[shadow070]

Deusentrieb,

I have had a look there already but for us tube noobs its not that clear yet, thats why the step by step explenation

 

[duesentrieb]

ok - with external points:

take corresponding fuse out.
insert DMM red probe to red socket, black probe to black, DMM set to 200mA DC
stick in screwdriver, which FITs the trimmer (!)
switch amp on, standby to run position, master =0
read
adjust carefully
switch off
put fuse back in

repeat for the other pairs

pics see official site (Einstein shown, same procedure though).

 

[duesentrieb]

ok - with external points:

take corresponding fuse out.
insert DMM red probe to red socket, black probe to black, DMM set to 200mA DC
stick in screwdriver, which FITs the trimmer (!)
switch amp on, standby to run position, master =0
read
adjust carefully
switch off
put fuse back in

repeat for the other pairs

pics see official site (Einstein shown, same procedure though).

 

[duesentrieb]

haven't found a step by step for biasing a Herbert yet?

would it be better to pull the chassis and use a Bias Rite?

Well - some years ago I've asked Peter to install the external points to his products (and he listened to me for the first time ) for faster adjustment.
But I guess his experience (and mine) with all the problems the average user (not saying you are) has with DMMs and stuff will result that newer Diezels won't have this feature anymore. Too many problems, too many user caused errors.

The bias rite is recommended by Diezel on the official site (for a good reason) for all guys who are looking for a simple, reliable and efficient method. I will ask Peter to keep at least the bias pot accessable from the outside (like with Einsteins and Herbert who have ext. points) - thats the most user friendly and SAFE option IMO.

 

[Peter Diezel]

Please repeat procedure 3 times because
the adjustment of a pair will influence
the other 2 pairs.

 

[nbarts]

But I guess his experience (and mine) with all the problems the average user (not saying you are) has with DMMs and stuff will result that newer Diezels won't have this feature anymore. Too many problems, too many user caused errors.

That's a shame! External points on my Herbert & Uberschall saved me a LOT of time & frustration.

 

[duesentrieb]

This adaptor costs 14 Euros (20 $) and is IMO much much easier to use than the method with the DMM alone. We just have to talk Peter into keeping the pot acessable from the outside. Flipping Herberts and VH4s may be good to work out, but also is a bit risky . . .

 

[Joeytpg]

Totally agree Olaf, it's a FUCKEN PITA! to get the Vh4 out of the headshell, turn it around, not brake a tube or bend something, try not to get shocked! GOD! I know it's the way it's been done for decades, but man, I REALLLY love that external pot accessibility! I wouldn't mind the Bias probe either, I already have one for my Vh4 biasing, it works great. I also like the way the Einstein is biased, very easy.... so again as long as I don't have to take the amp out of the headshell to access the bias trim pot it's all good!



By the way, Peter..... Is it possible to "mod" the vh4 so that the bias pot is accessible externally? (something tells me it's kind of impossible, but I can't hurt to ask )


P.S.
I'm waiting for the new flightcase I got from Thomann to send you the Vh4 Peter, I'll let you know once it's shipped.

 

[Capulin Overdrive]

Peter & Olaf, the external Bias Points kickass! and were major reason for wanting to get a Diezel, i hate having to pull the chassis!



thanks everybody! yea, i got impatient and found the tech corner at the Diezel Site, and got her done before reading this.



i turned the amp all the way off on the first set, after that i just went to standby for pulling and replacing the fuse, is that safe?


i didn't however recheck 2 or 3 times though, guess i should, but think i'm a little cold on everything?

 

[Capulin Overdrive]

This adaptor costs 14 Euros (20 $) and is IMO much much easier to use than the method with the DMM alone. We just have to talk Peter into keeping the pot acessable from the outside. Flipping Herberts and VH4s may be good to work out, but also is a bit risky . . .

YEP, external bias points kickass, and is defenantly a selling point!

 

[jcj]

But I guess his experience (and mine) with all the problems the average user (not saying you are) has with DMMs and stuff will result that newer Diezels won't have this feature anymore. Too many problems, too many user caused errors.

That's a shame! External points on my Herbert & Uberschall saved me a LOT of time & frustration.

Amen. Easiest thing in the world to do.

 

[jcj]

Peter & Olaf, the external Bias Points kickass! and were major reason for wanting to get a Diezel, i hate having to pull the chassis!



thanks everybody! yea, i got impatient and found the tech corner at the Diezel Site, and got her done before reading this.



i turned the amp all the way off on the first set, after that i just went to standby for pulling and replacing the fuse, is that safe?


i didn't however recheck 2 or 3 times though, guess i should, but think i'm a little cold on everything?

I would recheck. The bias can drift pretty hard.