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Old 16th October 2006, 05:12 AM   #1
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Default 269EX in a champ?

I was thinking about building a champ, after my first build ( EL84 powered dual preamp rocket! ) I want something a little cleaner.


will this transformer produce the needed 373v for the champ? ( do I need more/less?) Can't seem to find consistant voltage readings online for the champ 5f2...


I have the 269 EX in my amp right now and I'm measuring about 273v on the rectifier tube ( before rectification.) this is using it full wave, with the center tap grounded. Will using a fwb with no center tap give me the right voltage for the champ?
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Old 17th October 2006, 02:00 AM   #2
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Default Re: 269EX in a champ?

Quote:
Originally posted by ThSpeakerDude88
I was thinking about building a champ, after my first build ( EL84 powered dual preamp rocket! ) I want something a little cleaner.


will this transformer produce the needed 373v for the champ? ( do I need more/less?) Can't seem to find consistant voltage readings online for the champ 5f2...


I have the 269 EX in my amp right now and I'm measuring about 273v on the rectifier tube ( before rectification.) this is using it full wave, with the center tap grounded. Will using a fwb with no center tap give me the right voltage for the champ?

Im not sure about the 269EX in a stock Champ amplifier looks a bit shy on B+, But for sure the 272BX makes an excellent champ transformer.


I would think that the 269EX would work especially well with a tube like the EL84 or 6AQ5 even.

If you head over the the AX84.com site, there is a lot of data on using the EL84 In a SE type amp, If memory serves, That transformer is used in the P1 amp as well as a couple others.

269EX
Secondary: 190-0-190 V, 65 mA
Filament winding: 6.3 V, 2.5 A
Mounting centers: 1.75" x 1.56" vertical mount
Weight: 1.8 lbs.


272BX
Secondary: 300-0-300 V, 100 mA
Filament winding 1: 5 V, 2 A
Filament winding 2: 6.3 V, 3 A
Mounting centers: 2" x 2.19" vertical mount
Weight: 3.5 lbs.


I just built a champ (AA764)64 thru 67 blackface.
Used the 272BX and matches up great.

I designed an eyelet board especially to fit a cheapo hammond 13.5 X 2 Chassis.
Set it up with axial filter caps, Common sprague caps, and 1W carbon film resistors throughtout. Hole spacings are such that these carbon film 1w resistors fit correctly. Used Xircon 5W ceramics for Cathode bypass(6V6) and and power supply.

I could post a scan of the board, I have a dozen made up.

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Old 17th October 2006, 02:11 AM   #3
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I built the high octane, thats what the 269 is in

wish I could post some pictures, its a beautiful amp.

I'm not understanding this exactly....

190-0-190v.... shouldnt that give me 380v if I didn't use the center tap and I used a FWB rectifier instead of a 5y3 tube?

or are the trafo's designed to be used with the center tap? That seems like an awful lot of wasted potential voltage to me...I'm a lil confused about this
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Old 17th October 2006, 02:47 AM   #4
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Yes, that would give 380VAC. Now I assume you'd use a solid-state bridge (you'd need 3 tube rectifiers) - so there's only 2 Volts drop - and you get about 530VDC! If you use a 5Y3 and two SS diodes, that's "only" 500V. Even Leo Fender didn't push 6V6s that hard! Now you COULD use choke input to get around 360V... but it will still start out at 530V until the 6V6 starts drawing current. So you'll need stacked capacitors (450V WON'T do), and the solid state bridge needs to be protected by a varistor or a SMALL (.1-.5 uF) input cap.

Now this transformer wan't designed for FWB use, but I wouldn't worry about it at only 380V. DON'T even THINK you can get away with it with a 450-0-450 transformer...
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Old 17th October 2006, 03:16 AM   #5
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wow, so could I do with a smaller transformer? I want something with enough current capability btw to possibly run a 6L6
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Old 17th October 2006, 05:21 AM   #6
Trout is offline Trout  United States
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Quote:
Originally posted by ThSpeakerDude88
wow, so could I do with a smaller transformer? I want something with enough current capability btw to possibly run a 6L6
In all my PP 6L6 amps, I run 350-0-350 200ma with Tube Rect, I would think you would want to stay at least close to 100ma. on a SE amp. I have run 6L6GC's with a transformer rated at 300-0-300 70ma and it sounded good, but the transformer got pretty warm and I finally swapped it out.
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Old 18th October 2006, 02:19 AM   #7
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so 120ma to have some hearoom would be ok?
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