Bogner Uberschall Blue Rev - bias instructions for beginners

nbarts

New member
Unscrew the back panel. You don't really need to take the amp out of the shell, as you can access everything you need from here. In case you want to take the amp out of the shell for some reason there are 4 screws on the bottom of the amp. Turn the amp off, take the old power tubes out & put he new ones in (it has to be a matched quad). DO NOT touch the sockets! Connect a load to your amp first, turn the master & channel volumes all the way down, turn on the amp & leave it running for about 5 minutes. After that the manual has pretty much all you need.

"Common or ground plug insert is White color and the four individual tube plug inserts are Blue color. Set your multimeter to mV setting, 1mV = 1mA reading. Connect your multimeters ground test lead to the White/Common insert and the multimeters postive test lead to one Blue/Tube insert."

Bias adjustment thingy is circled in the picture. 32mA recommended.

uberb3.jpg
 

Lution

New member
I do the same thing and run an immediate check to make sure I'm not pushing too much into the new tubes, adjust down if needed, then let it warm up some before making the final adjustments.
 

cyndicate

Well-known member
nbarts":2miadajc said:
It reads 25 to 35 ma printed on the amp. Bogner support recommended me 32ma for JJ E34Ls.

Cool, thanks! I set mine to about 30, there is one tube though that is kind of out there, the other ones are around 30, and that one tube is running hotter than the rest at like 35.
 

cyndicate

Well-known member
nbarts":1mq4evi2 said:
Where did you get your tubes? They are not matched well.

I haven't replaced them yet, it's what was previously in here, it was just running way too hot previously so I backed it down a bit, going to order a new pair in the week or so.
 

nbarts

New member
psychodave":1j56ibid said:
FWIW, anytime I bias, I ALWAYS check the tubes right away. I want to make sure that at the current bias setting the tubes are not at 100% disp. While I have never had a situation at 100%, I would rather be safe than sorry. :thumbsup:

I do the same thing and run an immediate check to make sure I'm not pushing too much into the new tubes, adjust down if needed, then let it warm up some before making the final adjustments.

:2thumbsup:
 

just42dave

Well-known member
so black pointi tester lead goes in the white and red in the blue?????IM used to using a probe and when I used my tester on my jsx it blue the meter hahaha so ive been using the eurotubes probe which is a pain cuz i have to take each tube out etc,,, :confused:
 

just42dave

Well-known member
hell i havent even got the amp yet and from what im reading,,I feel like Ill hate it already.Can you get something other than death metal out of it???Im a big Chris poland fan and Jerry Cantrell,,They say the leads suck etc etc..AGHHHHHHHH
 

nbarts

New member
just42dave":uxjlbknz said:
hell i havent even got the amp yet and from what im reading,,I feel like Ill hate it already.Can you get something other than death metal out of it???Im a big Chris poland fan and Jerry Cantrell,,They say the leads suck etc etc..AGHHHHHHHH

First of all, nothing on the Uberschall sucks.
Second, the amp is advertised on the manufacturer's website as a metal amp, end of story.
 

elmagoo

New member
I know this is an old thread, but it helped me get my tubes swapped and I wanted to provide a bit more information for those looking in the future with regards to an issue I had.

I got this tip from Charlie who works at Bogner Amplification.

If you're switching from KT88s to EL34s and you find you can't get enough bias range from turning the white bias knob once you have the EL34s installed (mine could only go to 20mv), it's because there's an extra resistor they sometimes use when factory installing KT88s. Unfortunately I didn't take a pic when I had the chassis open, but it's easy enough to describe.

You'll have to take the screws out of the bottom so you can slide the amp chassis out a bit (you don't have to take it 100% of the way out). Now if you look at the underside of the chassis (i.e. the exposed side into the circuit boards and such), if you look on the main board right under where the white bias knob is located on the opposing side, you'll see there are two light blue resistors stacked on top of each other vertically (if you don't see two stacked resistors, then ignore all this and button her back up). Clip the top resistor off and that will extend the range of the white bias knob. They should be the only set of stacked resistors in that area, hence it should be easy to find. When done, button it back up and you're good to go. Just follow the procedure mentioned above in this thread to bias the amp.

I'd recommend taking the power tubes out before removing the chassis to avoid any risk of breaking them as my chassis was a bit finicky and I had to work it some to get it to un-stick from it's position.
 
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