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

THANKS VERY MUCH FOR YOUR HELP VERY GOOD!
found this somewhere on another forum thought i would post here for all to read

Here's how I do it:

1) If not using a bias probe, you need to have a 1 ohm resistor on each power tube socket (one end of resistor to ground; the other end tied to pins 1 & 8 ) Use a 1% tolerance resistor.

2) Turn power on and let tubes warm up. Switch standby to "on".

3) *Be very careful on this step (high voltages)*
Set your meter to the highest DC volts (600 or higher) and put the common (ground) lead in one of the chassis mounting nuts or alligator clip it. With one hand behind your back for safety, touch the positive lead to pin 3 (plate) of one of the power tubes. This is your plate or "B+" voltage. Write it down.

4) EL34's are 25 watts max and you want to set the bias to be between 60% and 70% maximum dissipation watts. (60% = 15 watts; 70% = 17.5 watts) Divide your desired wattage by your plate voltage from step 3. (example: 15/450 = .033 or 33mV) This is your desired bias voltage (probably between 30 and 40 mV).

5) Set your meter to lowest DCV setting (200mV or less) and touch the ground lead to the ground side of the 1 ohm resistor and the positive lead to the pin 1 side. Do this on all power tubes and adjust the tube with the highest value to your desired bias voltage from step 4.

Plate voltage will change a little when adjusting the bias so you may need to take another reading from pin 3 and adjust your equation accordingly and repeat steps 4 & 5.

And here is what nik sent me about biasing his amps

Ryan,
 
  The amp has only 1 bias pot. The tubes should match.
 
  All you need is a multimeter, and read in DC Volts.
 
  There are 4 jacks, 1 for each power tube, and 1 neg jack for the earth.
 
  Just adjust for 1 tube. Since the others match, the readings will be similar.
 
  Preamp tubes are self biasing, just plop em in,
 
Hope this helps, let me know.
 
_________________

On nic's layout the lines that go from cont... to dotted on main circ..board go under the board don't they?
and the lines that are only dotted on board are pre installed by nik when builds your board for the pack 2 kit and also are under board? I have inc.. a pic with these pointed out in green arrows

I am still making up my on weather to build the 2203 or 2204. the 2204's diagrahm is alot more clearer and better drawn. I feel i easily tackle the 2204. if you could load up a pretty large pic for me to look at that would be good. about same size as nic's diagrahm you loaded up.
it would also make up my mind on what one to build as either amp will be loud enough for gig use (playingat pubs and clubs) As for biasing i will use internal bias method testing resistor that runs on valve sockets across pin 8-1-resistor-ground. This is my first build adding external bias might complicate the build too much.
thanks ryan

Yeh, I'm gunna do whatt joe popp did build say 2 then sell them to get money back to buy a new one and also get the experience and then build maybe the 2203 on the third one when i have the exoerience under my belt.

sorry about the delay couldn't get into this site for about 1 week had to reset my modem when i found out othr people had acess and it was just me who could not get in.
yeh will be ordering one in about 2weeks. i'm thinking of doing a step-bystep instructions for the jcm800 and loading it on this site with lots of pics. like metroamps instructions i found on there forum.