wiring a 2203 PT

[phsyconoodler]

I have a 2203/JCM800 power transformer that has a center tap for using an HT fuse.I want to use the PT for a quad of 6L6's at a lower current level.Can I just wire it up without the HT center tap using a fullwave bridge rectifier or do I have to wire up the HT fuse like a Marshall?
  It's a bit odd the way the Marshall is done(to me at least)
Any insight would be appreciated.

[sluckey]

Say what? The 2203 schematic I'm looking at says the center tap is not used and shows it not connected to anything. The HT fuse is in the B+ rail between the bridge and the choke.

Just use a bridge and tape off the center tap like Marshall did. 

http://www.el34world.com/charts/Schematics/files/marshall/jcm800_lead_mstvol_100w_2203.pdf

[phsyconoodler]

If you look at this spec sheet it clearly shows the HT center tap on the same winding as the two 178v taps.

[sluckey]

Yes. And the schematic clearly shows that the center tap is not used. so, just ignore it.

[phsyconoodler]

Not so.The center tap is wired into the center of the filter caps where they meet in series .
   Like this.
 I know you are right and that I don't need to use it,but it's there for this purpose.

[sluckey]

That ain't a Marshall. Look at the schematic I posted. Now that's a Marshall. You specifically asked about Marshall, not a Ceriatone wanabee.

[phsyconoodler]

Yeah I have a marshall,the real deal and it has the Center tap too.Schematic or not. Not trying to stir up anything,just wonder why the real marshall and the ceriatone both have this 'center tap'.

[jerrydyer]

Nik doesnt wire his 2203 like stock 2203..    his PT's are all pretty close to this set up.

[phsyconoodler]

Indeed.The blue wire going to the filters is that HT center tap.And the Hoffman 100 watt PT shows this center tap too,just a different color.
  Wonder if the PT will work like a normal PT if you just ground that center tap?Then you don't need the full wave bridge?
 I'm tired and not quite understanding this anomaly right now.

[phsyconoodler]

Hoffman's 100 watt marshall PT.

[sluckey]

I have a 2203/JCM800 power transformer

Sorry for my confusion. I assumed you were talking about a Marshall JCM-800 series 2203. Marshall did two very similar 2203 amps. The JMP series 2203 has a power supply very similar to the Ceriatone layout. Your pic is similar to the Ceriatone layout and appears to be the JCM series also. The JCM-800 series 2203 does not use the center tap on the HT winding. (See pic below and/or look up the schematics for both amps.)

Not trying to stir up anything,just wonder why the real marshall and the ceriatone both have this 'center tap'.

And I was just funnin' with you. You did see the grin, right? All 3 amps have the center tap. Two use it, one doesn't. The JCM-800 series used caps that were rated at enough voltage to not need to connect caps in series or use the CT to balance the voltage across them.

Wonder if the PT will work like a normal PT if you just ground that center tap?Then you don't need the full wave bridge?

Are you talking about your Hammond PT? If so, sure it will. But your 178-0-178 Hammond will only produce 252VDC unloaded if you do. Using a bridge will double that figure to 504VDC unloaded, which is probably much closer to what you want for a quad of 6L6s.

Hopefully this pic will make the amp differences clearer. Both circuits were cropped from Dougs schematic library.


 

[phsyconoodler]

Thanks Sluckey.I just was wondering about that damn 'common' on those transformers.
  I'm just taping off the one on my Hammond PT and using the full wave bridge.It's easier that way for sure.
It's been a while since I built a 2203,about 5 years now.This one is being used in an Overdrive Rocket with 4-6L6's.

[jojokeo]

Using a CT or not is no big deal at all as long as it's wired like it should be for which ever way the voltages and ratings are for whatever tranny it is and how it's to be used. There's no set rule or tranny that's a "must have to build it this way" to use to build a certain amp with.