|
Title: Setting up and testing a ceriatone jcm800 2203 Post by: jcm800man on July 04, 2008, 11:30:04 AM I'm going to get a jcm800 2203 from nik at ceriatone with PPIMV mod in the pack2+JJ El34 tubes+ head cab package deal. I am fairly confident with the soldering and building of the amp and my father is trained in using a soldering iron as part of his job teaching welding and fitting ect... But the only thing I am unsure of is biasing and setting the new amp up.
If i was retubing say a second hand amp with the exact same tubes or doing a bias check on an old amp i would be probably right. It's just setting up and testing a new amp isn't as easy as retubing. Could someone explain this in simple idiots form. Lol... I understand how to work out what Ma to set poweramp tubes at you need to divide tube dissipation by the plate voltage and that give you 100% and as tubes run best at about 70% you divide by .7 So say that plate voltage was 470 and the EL34's tube dissipation is 25watts it would be 25 devide by 470 = 53Ma then times by .7 which = 37Ma. My questions are: how do you work out/measure plate voltage? dose nik's ceriatone jcm 800 2203 have a bias trim pot that ajust all vavles and if so were is it located using nik's jcm800 diagrahm? Are pre-amp tubes self biasing if not how do you bias these? many thanks in advance!!!!!!!! P.s. this will be my first build Title: Re: Setting up and testing a ceriatone jcm800 2203 Post by: cmoore on July 04, 2008, 06:10:36 PM If you have never built an amp before, I would say a 100 watt (or 50 for that matter) JCM 800 is a lot to start with. But HEY, if you already ordered it.... I do not know if I would get too concerned with math calculations. Jump on one of the many forums(Metro, Plexi, etc.) and you will see where most guys run there tubes in a 2203.
There will only be one bias pot, hence the need for a "Matched Quad" of tubes. The preamp tubes will not need to be biased or matched. I am just skimming the surface of all this of course. If you will, take this advice, join The Amp Garage and Metro Amps forums. Do as much reading as you can before your kit arrives. Pay special attention to the FAQ and "Stickys" at the beginning of each forum. Try to read as much as you can before bombarding the members with questions that they have heard a Billion time before. Use the SEARCH function on the forums before you ask a question. You will see that A LOT of your questions have already been asked and answered many times before. Good Luck Title: Re: Setting up and testing a ceriatone jcm800 2203 Post by: jcm800man on July 05, 2008, 12:23:57 AM Thanks, i will do that (go ask what Ma they have there el34's at)
Before posting my last question i read heaps and heaps on biasing buy not one information said how to work out plate voltage. the power in our county is 240volts would that have a differences as to what Ma i set the valves at? thanks |