Members Thmbs26 Posted March 6, 2010 Members Share Posted March 6, 2010 My fellow guitarist has a Peavey 6505 plus with two 6l6 in the middle and two KT66 at the both ends of the power tubes section. Can I just take a multimeter and plug it in through the back and read it off of there? I did that and received a reading of about 56. The guy at eurotubes told him that the back of the amp where you put in the test points are useless and that he would need a bias probe, what ever that means. We're really confused and need your help. Link to comment Share on other sites More sharing options...
Members MRAAJR Posted March 6, 2010 Members Share Posted March 6, 2010 Link to comment Share on other sites More sharing options...
Members BryanFTWL Posted March 6, 2010 Members Share Posted March 6, 2010 This Link to comment Share on other sites More sharing options...
Members wiseblood Posted March 6, 2010 Members Share Posted March 6, 2010 get a bias probe. This question is asked every day here. Link to comment Share on other sites More sharing options...
Members duncan Posted March 6, 2010 Members Share Posted March 6, 2010 I'm probably wrong, but you have to modify the amp to have a bias control added. Link to comment Share on other sites More sharing options...
Members Tawlks Posted March 6, 2010 Members Share Posted March 6, 2010 Tech. Link to comment Share on other sites More sharing options...
Members wiseblood Posted March 6, 2010 Members Share Posted March 6, 2010 You don't need a tech. It is dead simple to bias a amp.All the info you need is easily found on the net. Link to comment Share on other sites More sharing options...
Members Thmbs26 Posted March 6, 2010 Author Members Share Posted March 6, 2010 get a bias probe. This question is asked every day here. Would something like this be good? : http://taweber.powweb.com/biasrite/br_page.htm Link to comment Share on other sites More sharing options...
Members wiseblood Posted March 6, 2010 Members Share Posted March 6, 2010 That will work great. On the 6505 plus you may have to swap a resistor if you cannot get in the range you want. Actually I would just replace the 12k with a 6.8k while I had the amp opened up. Link to comment Share on other sites More sharing options...
Members Thmbs26 Posted March 6, 2010 Author Members Share Posted March 6, 2010 Hey, so what's the purpose for the test points at the rear of the amp? Link to comment Share on other sites More sharing options...
Members wiseblood Posted March 6, 2010 Members Share Posted March 6, 2010 I think they measure grid current. Link to comment Share on other sites More sharing options...
Members MRAAJR Posted March 6, 2010 Members Share Posted March 6, 2010 That will work great. On the 6505 plus you may have to swap a resistor if you cannot get in the range you want.Actually I would just replace the 12k with a 6.8k while I had the amp opened up. I am going to go out on a limb and say about that to 99.9% of HC what you just said might as well be Japanese. Link to comment Share on other sites More sharing options...
Members Whackmaster Posted March 6, 2010 Members Share Posted March 6, 2010 i dont think those bais test points are for adjusting the bais, I wouldnt leave those KT66 in there, unless you want a blown amp Link to comment Share on other sites More sharing options...
Members wiseblood Posted March 6, 2010 Members Share Posted March 6, 2010 I thought kt66 and 6l6 were interchangeable. Maybe not. Link to comment Share on other sites More sharing options...
Members Beavis808 Posted March 6, 2010 Members Share Posted March 6, 2010 You can't bias a 6505 unless its modded, right? Link to comment Share on other sites More sharing options...
Members wiseblood Posted March 6, 2010 Members Share Posted March 6, 2010 Right but he has a plus. Link to comment Share on other sites More sharing options...
Members shredloud Posted March 6, 2010 Members Share Posted March 6, 2010 The Eurotubes websites has all Peavey biasing info you will ever need... check it out. I bought my bias probe from them for 20 bux, hook it into a multimeter and bam you got your reading.. Link to comment Share on other sites More sharing options...
Members Dewysoss Posted March 6, 2010 Members Share Posted March 6, 2010 Right but he has a plus. which still has a retardedly small bias range. Link to comment Share on other sites More sharing options...
Members wiseblood Posted March 6, 2010 Members Share Posted March 6, 2010 Yeah. it was by design though.do they sound better hotter? I don't know that is subjective. They do sound different. Link to comment Share on other sites More sharing options...
Members O'Rourke Posted March 6, 2010 Members Share Posted March 6, 2010 The 6505+ should have an external bias trim pot on top of the chassis. The bias mod that needs to be done to those is changing a resistor to give the pot more range, you won't be able to get a stock one hot enough. The 5150/5150II needs to have a pot added to adjust the bias AFAIK. Link to comment Share on other sites More sharing options...
Members metalone Posted March 7, 2010 Members Share Posted March 7, 2010 I did this mod on my 6505+ it is really easy, the stock one will not get you where you want to go Link to comment Share on other sites More sharing options...
Members FappyTheClown Posted March 9, 2010 Members Share Posted March 9, 2010 Bias mod is most definitely a plus in my book. The bias points on the back are not completely useless. Setting your meter to DCV, getting a reading of about -45-47 volts evokes the best combination of clarity and crunch, getting you out of crossover distortion range, and it's perfectly within the tubes' plate dissipation safety zone. Link to comment Share on other sites More sharing options...
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