uberschall kt88 swap resistor question

[MYLILSS]

when adding kt88's to a bogner uberschall, i know you typically have to add a resistor or two to get it in range. are the new resistors put in place of the originals or are they piggybacked onto the originals ?

mike

 

[steve_k]

when adding kt88's to a bogner uberschall, i know you typically have to add a resistor or two to get it in range. are the new resistors put in place of the originals or are they piggybacked onto the originals ?

mike

You will need to add to. They will need to be paralleled though, not series (leg to leg in and out). There's probably a single 22K in there now. Most likely a 33K paralleled will put you in range. I can't remember what the Uber bias circuit has in it. But, suggest you check and make sure though as this is from my experience with the TJ and going the other way.

Now that is out of the way.......WHY?

Just a suggestion, if you want to add some head room but retain the Uber grunt, try a quad of JJ KT77's. They will drop in with the same bias range.

Steve

 

[MYLILSS]

it is actually my buddy's amp. his main reason is to help out the clean channel some... i didnt even think about mentioning the kt77's when we were talking about a tube swap.

right now there are two resistors side by side. they are soldered in weird though (IMO). one resistor goes through both through holes in the psb, and the other resistor right beside it, has one leg going into a through hole on the pcb and the other leg bends back around and to one of the legs of the resistor right beside it

 

[steve_k]

Can you determine what values they are?

 

[MYLILSS]

here is a picture. i tried to determine the value but i havent seen resistors with this many color bands before. it looks like it has been tampered with before, although i dont know at what point because it was bought used. i have never seen any factory job that looked like this

 

[wIsEbLooD]

Anyone tried 6ca7's in the uber?

 

[RockStarNick]

here is a picture. i tried to determine the value but i havent seen resistors with this many color bands before. it looks like it has been tampered with before, although i dont know at what point because it was bought used. i have never seen any factory job that looked like this

Does not look like a factory job at all. The inside of all of my Bogners look super tidy. that kinda looks messy.

Just look up "5 band color code resistor" on google, and you should get some sort of calculator to help.

 

[MYLILSS]

Anyone tried 6ca7's in the uber?

That would be interesting to hear. I think we are just gonna go with some kt77's. See how they sound in this amp

 

[wIsEbLooD]

I think I will try it in my rev blue if they will bias up properly.