Tube Biasing Question

[Padrino]

So...i picked up this old HRDx for 50 bucks (it was in pretty bad shape). Long story short, the thing was barely working, so i'm deciding to make it a project. I ordered a mode kit from Frommel electronics to recap everything, and got a new set of tubes to swap out, as well as a new speaker (thing was still fitted with the stock speaker )

 

I was talking to my professor, who is also a guitarist, and he said i will need to bias the tubes before i put them in, as well as rebiasing the amp.

 

I'm an engineer, but my EE knowledge doesnt really extend this far. What do i need to do to bias the tubes and rebias the amp? or do i even need to do it?

[pine]

The tubes are what they are, you can't bias them by themselves. there is nothing on a tube that is adjustable. You put the new tubes in and then bias the amp for those tubes. A worthwhile piece of equipment to get is the Weber Bias Rite probe which will allow you to take readings off the power tubes without danger of electrocution, You can find the probe and a link to its use at the Weber website https://taweber.powweb.com/biasrite/br_page.htm

 

 

PS I just noticed that you are in State College, which is where I live, when you're finished with the rebuild and ready for the new tubes PM me and you can bring it over and I'll show you how with my Bias Rite

[hecticone]

Depending on what year that speaker might be pretty darn nice.

[knucklefux]

ask your professor how to bias tubes

[whatsaguitar]

 

The tubes are what they are, you can't bias them by themselves. there is nothing on a tube that is adjustable. You put the new tubes in and then bias the amp for those tubes. A worthwhile piece of equipment to get is the Weber Bias Rite probe which will allow you to take readings off the power tubes without danger of electrocution, You can find the probe and a link to its use at the Weber website https://taweber.powweb.com/biasrite/br_page.htm PS I just noticed that you are in State College, which is where I live, when you're finished with the rebuild and ready for the new tubes PM me and you can bring it over and I'll show you how with my Bias Rite

 

 

hows the bias rite compare to the bias king?

[pine]

 

hows the bias rite compare to the bias king?

 

 

 

I wish I could afford a Bias King, it's way easier to use, I just have the $60 Bias Rite Adapter Head w/VI option

[davydusade]

I biased my HRD at about 38 ma with 6l6's and It was teh Juizy cleans ,,hit it with an od on the clean and yer in heaven..Now the dirt side FAIL no matter what ya try..

[VanR]

I got one of the $25 Eurotubes bias probes and use my Radio Shack digital multimeter and it works fine.